Evolutionary psychology

Evolutionary psychology

Overview
Evolutionary psychology (EP) is an approach in the social and natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...

s that examines psychological traits
Trait theory
In psychology, Trait theory is a major approach to the study of human personality. Trait theorists are primarily interested in the measurement of traits, which can be defined as habitual patterns of behavior, thought, and emotion. According to this perspective, traits are relatively stable over...

 such as memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

, perception
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...

, and language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

 from a modern evolutionary perspective
Modern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...

. It seeks to identify which human psychological traits are evolved adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s, that is, the functional products of natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 or sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

. Adaptationist thinking about physiological mechanisms, such as the heart, lungs, and immune system, is common in evolutionary biology.
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Encyclopedia
Evolutionary psychology (EP) is an approach in the social and natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...

s that examines psychological traits
Trait theory
In psychology, Trait theory is a major approach to the study of human personality. Trait theorists are primarily interested in the measurement of traits, which can be defined as habitual patterns of behavior, thought, and emotion. According to this perspective, traits are relatively stable over...

 such as memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

, perception
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...

, and language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

 from a modern evolutionary perspective
Modern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...

. It seeks to identify which human psychological traits are evolved adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s, that is, the functional products of natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 or sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

. Adaptationist thinking about physiological mechanisms, such as the heart, lungs, and immune system, is common in evolutionary biology. Evolutionary psychology applies the same thinking to psychology, arguing that the mind has a modular structure
Modularity of mind
Modularity of mind is the notion that a mind may, at least in part, be composed of separate innate structures which have established evolutionarily developed functional purposes...

 similar to that of the body, with different modular adaptations serving different functions. Evolutionary psychologists argue that much of human behavior is the output of psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s that evolved to solve recurrent problems in human ancestral environments.

The adaptationist approach is steadily increasing as an influence in the general field of psychology.

Evolutionary psychologists suggest that EP is not simply a subdiscipline of psychology but that evolutionary theory can provide a foundational, metatheoretical framework that integrates the entire field of psychology, in the same way it has for biology.

Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations including the abilities to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, and cooperate with others. They report successful tests of theoretical predictions related to such topics as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.

The theories and findings of EP have applications in many fields, including economics
Economics
Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...

, law
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

, psychiatry
Psychiatry
Psychiatry is the medical specialty devoted to the study and treatment of mental disorders. These mental disorders include various affective, behavioural, cognitive and perceptual abnormalities...

, politics
Politics
Politics is a process by which groups of people make collective decisions. The term is generally applied to the art or science of running governmental or state affairs, including behavior within civil governments, but also applies to institutions, fields, and special interest groups such as the...

, and literature
Literature
Literature is the art of written works, and is not bound to published sources...

.

Controversies concerning EP involve questions of testability, cognitive and evolutionary assumptions (such as modular functioning of the brain or the ancestral environment), importance of non-genetic and non-adaptive explanations, as well as political and ethical issues due to interpretations of research results.

Principles


Evolutionary psychology is an approach that views human nature
Human nature
Human nature refers to the distinguishing characteristics, including ways of thinking, feeling and acting, that humans tend to have naturally....

 as a universal set of evolved psychological adaptations to recurring problems in the ancestral environment. It refers to sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, a systematic study in biological basis in gender behaviour. Proponents of EP suggest that it seeks to heal a fundamental division at the very heart of science --- that between the soft human social sciences and the hard natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...

s, recognizing that human beings are living organisms, which motivates understanding psychology
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

 as a branch of biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

. Anthropologist John Tooby
John Tooby
John Tooby is an American anthropologist, who, together with psychologist wife Leda Cosmides, helped pioneer the field of evolutionary psychology....

 and psychologist Leda Cosmides
Leda Cosmides
Leda Cosmides, is an American psychologist, who, together with anthropologist husband John Tooby, helped develop the field of evolutionary psychology....

 note:

"Evolutionary psychology is the long-forestalled scientific attempt to assemble out of the disjointed, fragmentary, and mutually contradictory human disciplines a single, logically integrated research framework for the psychological, social, and behavioral sciences—a framework
that not only incorporates the evolutionary sciences on a full and equal basis, but that systematically works out all of the revisions in existing belief and research practice that such a synthesis requires."


Just as human physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

 and evolutionary physiology
Evolutionary physiology
Evolutionary physiology is the study of physiological evolution, which is to say, the manner in which the functional characteristics of individuals in a population of organisms have responded to selection across multiple generations during the history of the population.It is a subdiscipline of both...

 have worked to identify physical adaptations of the body that represent "human physiological nature," the purpose of evolutionary psychology is to identify evolved emotional and cognitive adaptations that represent "human psychological nature." EP is, to quote Steven Pinker
Steven Pinker
Steven Arthur Pinker is a Canadian-American experimental psychologist, cognitive scientist, linguist and popular science author...

, "not a single theory but a large set of hypotheses" and a term which "has also come to refer to a particular way of applying evolutionary theory to the mind, with an emphasis on adaptation, gene-level selection, and modularity
Modularity of mind
Modularity of mind is the notion that a mind may, at least in part, be composed of separate innate structures which have established evolutionarily developed functional purposes...

." Evolutionary psychology adopts an understanding of the mind that is based on the computational theory of mind
Computational theory of mind
In philosophy, the computational theory of mind is the view that the human mind is an information processing system and that thinking is a form of computing. The theory was proposed in its modern form by Hilary Putnam in 1961 and developed by Jerry Fodor in the 60s and 70s...

. It describes mental processes as computational operations, so that for example a fear response is described as arising from a neurological computation that inputs the perceptional data, e.g. a visual image of a spider and outputs the appropriate reaction, e.g. fear of possibly dangerous animals.

While philosophers have generally considered human mind to include broad faculties, such as reason and lust, evolutionary psychologists describe evolved psychological mechanisms as narrowly focused to deal with specific issues, such as catching cheaters or choosing mates. EP views the human brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

 as comprising many functional mechanisms, called psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s
or evolved cognitive mechanisms or cognitive modules, designed by the process of natural selection. Examples include language-acquisition modules
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...

, incest-avoidance mechanisms
Westermarck effect
The Westermarck effect, or reverse sexual imprinting, is a hypothetical psychological effect through which people who live in close domestic proximity during the first few years of their lives become desensitized to later sexual attraction. This phenomenon was first hypothesized by Finnish...

, cheater-detection mechanisms
Wason selection task
Devised in 1966 by Peter Cathcart Wason, the Wason selection task, one of the most famous tasks in the psychology of reasoning, is a logic puzzle which is formally equivalent to the following question:...

, intelligence and sex
Sex
In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

-specific mating preferences, foraging mechanisms, alliance-tracking mechanisms, agent-detection mechanisms, and others. Some mechanisms, termed domain-specific, deal with recurrent adaptive problems over the course of human evolutionary history. Domain-general mechanisms, on the other hand, are proposed to deal with evolutionary novelty.

EP has roots in cognitive psychology
Cognitive psychology
Cognitive psychology is a subdiscipline of psychology exploring internal mental processes.It is the study of how people perceive, remember, think, speak, and solve problems.Cognitive psychology differs from previous psychological approaches in two key ways....

 and evolutionary biology but also draws on behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

, artificial intelligence
Artificial intelligence
Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...

, genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

, ethology
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....

, anthropology
Anthropology
Anthropology is the study of humanity. It has origins in the humanities, the natural sciences, and the social sciences. The term "anthropology" is from the Greek anthrōpos , "man", understood to mean mankind or humanity, and -logia , "discourse" or "study", and was first used in 1501 by German...

, archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

, biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, and zoology
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

. EP is closely linked to sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, but there are key differences between them including the emphasis on domain-specific rather than domain-general mechanisms, the relevance of measures of current fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

, the importance of mismatch theory
Mismatch theory
Mismatch theory is a concept in evolutionary biology that refers to fluidity in fitness criteria.The essence of mismatch theory is that organisms possess traits that have been passed down through generations, preserved by natural selection because of their adaptive function in a given environment...

, and psychology rather than behaviour. Most of what is now labeled as sociobiological research is now confined to the field of behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

.

Nikolaas Tinbergen
Nikolaas Tinbergen
Nikolaas "Niko" Tinbergen was a Dutch ethologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning organization and elicitation of individual and social behaviour patterns in animals.In the 1960s he...

's four categories of questions
Tinbergen's four questions
Tinbergen's four questions, named after Nikolaas Tinbergen, are complementary categories of explanations for behavior. It suggests that an integrative understanding of behavior must include both a proximate and ultimate analysis of behavior, as well as an understanding of both...

 can help to clarify the distinctions between several different, but complementary, types of explanations. Evolutionary psychology focuses primarily on the "why?" questions, while traditional psychology focuses on the "how?" questions.
Sequential vs. Static Perspective
Historical/Developmental
Explanation of current form in terms of a historical sequence
Current Form
Explanation of the current form of species
How vs. Why Questions Proximate
How an individual organism's structures function
Ontogeny
Developmental explanations for changes in individuals, from DNA to their current form
Mechanism
Mechanistic explanations for how an organism's structures work
Evolutionary
Why a species evolved the structures (adaptations) it has
Phylogeny
The history of the evolution of sequential changes in a species over many generations
Adaptation
A species trait that evolved to solve a reproductive or survival problem in the ancestral environment

Premises


Evolutionary psychology is founded on several core premises.
  1. The brain is an information processing device, and it produces behavior in response to external and internal inputs.
  2. The brain's adaptive mechanisms were shaped by natural and sexual selection.
  3. Different neural mechanisms are specialized for solving problems in humanity's evolutionary past.
  4. The brain has evolved specialized neural mechanisms that were designed for solving problems that recurred over deep evolutionary time, giving modern humans Stone age minds.
  5. Most contents and processes of the brain are unconscious; and most mental problems that seem easy to solve are actually extremely difficult problems that are solved unconsciously by complicated neural mechanisms.
  6. Human psychology consists of many specialized mechanisms, each sensitive to different classes of information or inputs. These mechanisms combine to produce manifest behavior.

History



Evolutionary psychology has its historical roots in Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

’s theory of natural selection. In The Origin of Species Darwin predicted that psychology would develop an evolutionary basis:

Two of his later books were devoted to the study of animal emotions and psychology; The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex is a book on evolutionary theory by English naturalist Charles Darwin, first published in 1871. It was Darwin's second great book on evolutionary theory, following his 1859 work, On The Origin of Species. In The Descent of Man, Darwin applies...

in 1871 and The Expression of the Emotions in Man and Animals
The Expression of the Emotions in Man and Animals
The Expression of the Emotions in Man and Animals is a book by Charles Darwin, published in 1872, concerning genetically determined aspects of behaviour. It was published thirteen years after On The Origin of Species and is, along with his 1871 book The Descent of Man, Darwin's main consideration...

in 1872. Darwin's work inspired William James
William James
William James was a pioneering American psychologist and philosopher who was trained as a physician. He wrote influential books on the young science of psychology, educational psychology, psychology of religious experience and mysticism, and on the philosophy of pragmatism...

’s functionalist approach to psychology.

The content of EP has derived from, on the one hand, the biological sciences (especially evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary theory as it relates to ancient human environments, the study of paleoanthropology
Paleoanthropology
Paleoanthropology, which combines the disciplines of paleontology and physical anthropology, is the study of ancient humans as found in fossil hominid evidence such as petrifacted bones and footprints.-19th century:...

 and animal behavior) and, on the other, the human sciences especially psychology.

Evolutionary biology as an academic discipline
Academic discipline
An academic discipline, or field of study, is a branch of knowledge that is taught and researched at the college or university level. Disciplines are defined , and recognized by the academic journals in which research is published, and the learned societies and academic departments or faculties to...

 emerged with the modern evolutionary synthesis
Modern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...

 in the 1930s and 1940s. In the 1930s the study of animal behaviour (ethology
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....

) emerged with the work of Dutch biologist Nikolaas Tinbergen
Nikolaas Tinbergen
Nikolaas "Niko" Tinbergen was a Dutch ethologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning organization and elicitation of individual and social behaviour patterns in animals.In the 1960s he...

 and Austrian biologists Konrad Lorenz
Konrad Lorenz
Konrad Zacharias Lorenz was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize with Nikolaas Tinbergen and Karl von Frisch...

  and Karl von Frisch
Karl von Frisch
Karl Ritter von Frisch was an Austrian ethologist who received the Nobel Prize in Physiology or Medicine in 1973, along with Nikolaas Tinbergen and Konrad Lorenz....

.

W.D. Hamilton's (1964) papers on inclusive fitness
Inclusive fitness
In evolutionary biology and evolutionary psychology, the inclusive fitness of an organism is the sum of its classical fitness and the number of equivalents of its own offspring it can add to the population by supporting others...

 and Robert Trivers
Robert Trivers
Robert L. Trivers is an American evolutionary biologist and sociobiologist and Professor of Anthropology and Biological Sciences at Rutgers University. Trivers is most noted for proposing the theories of reciprocal altruism , parental investment , facultative sex ratio determination , and...

's (1972) theories on reciprocity
Reciprocity (evolution)
Reciprocity in evolutionary biology refers to mechanisms whereby the evolution of cooperative or altruistic behaviour may be favoured by the probability of future mutual interactions...

 and parental investment
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

 helped to establish evolutionary thinking in psychology and the other social sciences. In 1975, E O Wilson combined evolutionary theory with studies of animal and social behavior, building on the works of Lorenz and Tinbergen, in his book Sociobiology:The New Synthesis.

In the 1970s, two major branches developed from ethology. Firstly, the study of animal social behavior (including humans) generated sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, defined by its pre-eminent proponent Edward O. Wilson in 1975 as "the systematic study of the biological basis of all social behavior" and in 1978 as "the extension of population biology and evolutionary theory to social organization". Secondly, there was behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

 which placed less emphasis on social behavior by focusing on the ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

  and evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary basis of both animal and human
Human behavioral ecology
Human behavioral ecology or human evolutionary ecology applies the principles of evolutionary theory and optimization to the study of human behavioral and cultural diversity. HBE examines the adaptive design of traits, behaviors, and life histories of humans in an ecological context...

 behavior.

In the 1970s and 1980s university departments began to include the term evolutionary biology in their titles. The modern era of evolutionary psychology was ushered in, in particular, by Donald Symons
Donald Symons
Donald Symons is an American anthropologist who is best known as one of the founders of evolutionary psychology, and for pioneering the study of human sexuality from an evolutionary perspective...

' 1979 book The Evolution Human Sexuality and Tooby and Cosmides 1992 book The Adapted Mind
The Adapted Mind
The Adapted Mind: Evolutionary Psychology and the Generation of Culture is an edited volume, first published in 1992 by Oxford University Press, edited by Jerome Barkow, Leda Cosmides and John Tooby...

.

From psychology there are the primary streams of developmental
Developmental psychology
Developmental psychology, also known as human development, is the scientific study of systematic psychological changes, emotional changes, and perception changes that occur in human beings over the course of their life span. Originally concerned with infants and children, the field has expanded to...

, social
Social psychology
Social psychology is the scientific study of how people's thoughts, feelings, and behaviors are influenced by the actual, imagined, or implied presence of others. By this definition, scientific refers to the empirical method of investigation. The terms thoughts, feelings, and behaviors include all...

 and cognitive psychology
Cognitive psychology
Cognitive psychology is a subdiscipline of psychology exploring internal mental processes.It is the study of how people perceive, remember, think, speak, and solve problems.Cognitive psychology differs from previous psychological approaches in two key ways....

. Establishing some measure of the relative influence of genetics and environment on behavior has been at the core of behavioral genetics and its variants, notably studies at the molecular level that examine the relationship between genes, neurotransmitters and behavior. Dual inheritance theory
Dual inheritance theory
Dual inheritance theory , also known as gene-culture coevolution, was developed in the late 1970s and early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution...

 (DIT), developed in the late 1970s and early 1980s, has a slightly different perspective by trying to explain how human behavior
Human behavior
Human behavior refers to the range of behaviors exhibited by humans and which are influenced by culture, attitudes, emotions, values, ethics, authority, rapport, hypnosis, persuasion, coercion and/or genetics....

 is a product of two different and interacting evolutionary processes: genetic evolution  and cultural evolution. DIT is a "middle-ground" between much of social science, which views culture
Culture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...

  as the primary cause of human behavioral variation, and human sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

  and evolutionary psychology which view culture as an insignificant by-product of genetic selection.

Theoretical foundations


The theories on which evolutionary psychology is based originated with Charles Darwin's work, including his speculations about the evolutionary origins of social instincts in humans. Modern evolutionary psychology, however, is possible only because of advances in evolutionary theory in the 20th century.

Evolutionary psychologists say that natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 has provided humans with many psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s, in much the same way that it generated humans' anatomical and physiological adaptations. As with adaptations in general, psychological adaptations are said to be specialized for the environment in which an organism evolved, the environment of evolutionary adaptedness, or EEA. Sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

 provides organisms with adaptations related to mating. For male mammals, which have a relatively fast reproduction rate, sexual selection leads to adaptations that help them compete for females. For female mammals, with a relatively slow reproduction rate, sexual selection leads to choosiness, which helps females select higher quality mates. Charles Darwin described both natural selection and sexual selection, but he relied on group selection to explain the evolution of self-sacrificing behavior. Group selection is a weak explanation because in any group the less self-sacrificing animals will be more likely to survive and the group will become less self-sacrificing.

In 1964, William D. Hamilton proposed inclusive fitness
Inclusive fitness
In evolutionary biology and evolutionary psychology, the inclusive fitness of an organism is the sum of its classical fitness and the number of equivalents of its own offspring it can add to the population by supporting others...

 theory, emphasizing a "gene's-eye
Gene-centered view of evolution
The gene-centered view of evolution, gene selection theory or selfish gene theory holds that evolution occurs through the differential survival of competing genes, increasing the frequency of those alleles whose phenotypic effects successfully promote their own propagation, with gene defined as...

" view of evolution. Hamilton noted that individuals can increase the replication of their genes into the next generation by helping close relatives with whom they share genes survive and reproduce. According to "Hamilton's rule", a self-sacrificing behavior can evolve if it helps close relatives so much that it more than compensates for the individual animal's sacrifice. Inclusive fitness theory resolved the issue of how "altruism" evolved. Other theories also help explain the evolution of altruistic behavior, including evolutionary game theory
Evolutionary game theory
Evolutionary game theory is the application of Game Theory to evolving populations of lifeforms in biology. EGT is useful in this context by defining a framework of contests, strategies and analytics into which Darwinian competition can be modelled. It originated in 1973 with John Maynard Smith...

, tit-for-tat reciprocity, and generalized reciprocity. These theories not only help explain the development of altruistic behavior but also account for hostility toward cheaters (individuals that take advantage of others' altruism).

Several mid-level evolutionary theories inform evolutionary psychology. The r/K selection theory proposes that some species prosper by having many offspring while others follow the strategy of having fewer offspring but investing much more in each one. Humans follow the second strategy. Parental investment
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

 theory explains how parents invest more or less in individual offspring based on how successful those offspring are likely to be, and thus how much they might improve the parents' inclusive fitness. According to the Trivers-Willard hypothesis
Trivers-Willard hypothesis
In evolutionary biology, the Trivers–Willard hypothesis, formally proposed by Robert Trivers and Dan Willard, predicts greater investment in males by parents in good conditions and greater investment in females by parents in poor conditions...

, parents in good conditions tend to invest more in sons (who are best able to take advantage of good conditions), while parents in poor conditions tend to invest more in daughters (who are best able to have successful offspring even in poor conditions). According to life history theory
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...

, animals evolve life histories to match their environments, determining details such as age at first reproduction and number of offspring. Dual inheritance theory
Dual inheritance theory
Dual inheritance theory , also known as gene-culture coevolution, was developed in the late 1970s and early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution...

 posits that genes and human culture have interacted, with genes affecting the development of culture and culture, in turn, affecting human evolution on a genetic level (see also the Baldwin effect
Baldwin effect
The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is a theory of a possible evolutionary processes that was originally put forward in 1896 in a paper, "A New Factor in Evolution," by American psychologist James Mark Baldwin. The paper proposed a mechanism for specific...

).

Evolved psychological mechanisms



Evolutionary psychology is based on the hypothesis that, just like hearts, lungs, livers, kidneys, and immune systems, cognition has functional structure that has a genetic basis, and therefore has evolved by natural selection. Like other organs and tissues, this functional structure should be universally shared amongst a species, and should solve important problems of survival and reproduction.

Evolutionary psychologists seek to understand psychological mechanisms
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

 by understanding the survival and reproductive functions they might have served over the course of evolutionary history. These might include abilities to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, cooperate with others. Consistent with the theory of natural selection, evolutionary psychology sees humans as often in conflict with others, including mates and relatives. Even mothers sometimes struggle with their children over weaning, which benefits the mother more than the child. Evolutionary psychology also recognizes the role of kin selection and reciprocity in evolving prosocial traits such as altruism. Like chimps and bonobos, humans have subtle and flexible social instincts, allowing them to form extended families, lifelong friendships, and political alliances. In studies testing theoretical predictions, evolutionary psychologists have made modest findings on topics such as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.

Products of evolution: adaptations, exaptations, byproducts, and random variation


Not all traits of organisms are adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s. As noted in the table below, traits may also be exaptation
Exaptation
Exaptation, cooption, and preadaptation are related terms referring to shifts in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another. Exaptations are common in both anatomy and behaviour...

s, byproducts of adaptations (sometimes called "spandrels"), or random variation between individuals.

Psychological adaptations are hypothesized to be innate or relatively easy to learn, and to manifest in cultures worldwide. For example, the ability of toddlers to learn a language with virtually no training is likely to be a psychological adaptation. On the other hand, ancestral humans did not read or write, thus today learning to read and write require extensive training, and presumably represent byproducts of cognitive processing that use psychological adaptations designed for other functions.
Adaptation Exaptation By-Product Random Noise
Definition Organismic trait designed to solve an ancestral problem(s). Shows complexity, special "design", functionality Adaptation that has been "re-designed" to solve a different adaptive problem. Byproduct of an adapative mechanism with no current or ancestral function Random variations in an adaptation or byproduct
Physiological Example Bones / Umbilical cord Small bones of the inner ear White color of bones / Belly button Bumps on the skull, convex or concave belly button shape
Psychological Example Toddlers’ ability to learn to talk with minimal instruction. Voluntary Attention Ability to learn to read and write. Within-sex variations in voice pitch.


One of the tasks of evolutionary psychology is to identify which psychological traits are likely to be adaptations, byproducts or random variation. George C Williams suggested that an "adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

 is a special and onerous concept that should only be used where it is really necessary". As noted by Williams and others, adaptations can be identified by their improbable complexity, species universality, and adaptive functionality.

Obligate and facultative adaptations


A question that may be asked about an adaptation is whether it is generally obligate (relatively robust in the face of typical environmental variation) or facultative (sensitive to typical environmental variation). The sweet taste of sugar and the pain of hitting one's knee against concrete are the result of fairly obligate psychological adaptations; typical environmental variability during development does not much affect their operation. By contrast, facultative adaptations are somewhat like "if-then" statements. For example, adult attachment style seems particularly sensitive to early childhood experiences. As adults, the propensity to develop close, trusting bonds with others is dependent on whether early childhood caregivers could be trusted to provide reliable assistance and attention. The adaptation for skin to tan is conditional to exposure to sunlight; this is an example of another facultative adaptation. When a psychological adaptation is facultative, evolutionary psychologists concern themselves with how developmental and environmental inputs influence the expression of the adaptation.

Cultural universals



Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations. Cultural universals include behaviors related to language, cognition, social roles, gender roles, and technology. Evolved psychological adaptations (such as the ability to learn a language) interact with cultural inputs to produce specific behaviors (e.g., the specific language learned). Basic gender differences, such as greater eagerness for sex among men and greater coyness among women, are explained as sexually dimorphic psychological adaptations that reflect the different reproductive strategies of males and females. Evolutionary psychologists contrast their approach to what they term the "standard social science model
Standard social science model
The term the Standard Social Science Model was first introduced to a wide audience by John Tooby and Leda Cosmides in the 1992 edited volume The Adapted Mind, to describe the "blank slate," social constructionist,or "cultural determinist" perspective that they claim is the dominant theoretical...

," according to which the mind is a general-purpose cognition device shaped almost entirely by culture.

Environment of evolutionary adaptedness



EP argues that to properly understand the functions of the brain, one must understand the properties of the environment in which the brain evolved. That environment is often referred to as the "environment of evolutionary adaptedness" (EEA).

The term "environment of evolutionary adaptedness" was coined by John Bowlby
John Bowlby
Edward John Mostyn "John" Bowlby was a British psychologist, psychiatrist and psychoanalyst, notable for his interest in child development and for his pioneering work in attachment theory.- Family background :...

 as part of attachment theory
Attachment theory
Attachment theory describes the dynamics of long-term relationships between humans. Its most important tenet is that an infant needs to develop a relationship with at least one primary caregiver for social and emotional development to occur normally. Attachment theory is an interdisciplinary study...

. It refers to the environment to which a particular evolved mechanism is adapted. More specifically, the EEA is defined as the set of historically recurring selection pressures that formed a given adaptation, as well as those aspects of the environment that were necessary for the proper development and functioning of the adaptation.

Humans, comprising the genus Homo
Homo (genus)
Homo is the genus that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis....

, appeared between 1.5 and 2.5 million years ago, a time that roughly coincides with the start of the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 1.8 million years ago. Because the Pleistocene ended a mere 12,000 years ago, most human adaptations either newly evolved during the Pleistocene, or were maintained by stabilizing selection
Stabilizing selection
-Description:Stabilizing or ambidirectional selection, , is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. This is probably the most common mechanism of action for natural selection...

 during the Pleistocene. Evolutionary psychology therefore proposes that the majority of human psychological mechanisms are adapted to reproductive problems frequently encountered in Pleistocene environments. In broad terms, these problems include those of growth, development, differentiation, maintenance, mating, parenting, and social relationships.

The EEA is significantly different from modern society. Our ancestors lived in smaller groups, had more cohesive cultures, and had more stable and rich contexts for identity and meaning. Researchers look to existing hunter-gatherer societies for clues as to how our hunter-gatherer ancestors lived. Since hunter-gatherer societies are egalitarian, the ancestral population may have been egalitarian as well, a social pattern different from the hierarchies found in chimp bands. Unfortunately, the few surviving hunter-gatherer societies are different from each other, and they have been pushed out of the best land and into harsh environments, so it is not clear how closely they reflect ancestral culture.

Evolutionary psychologists sometimes look to chimpanzees, bonobos, and other great apes for insight into human ancestral behavior. Christopher Ryan and Cacilda Jetha argue that evolutionary psychologists have overemphasized our similarity to chimps, which are more violent, while underestimating our similarity to bonobos, which are more peaceful.

Mismatches


Since an organism's adaptations were suited to its ancestral environment, a new and different environment can create a mismatch. Because humans are mostly adapted to Pleistocene environments, psychological mechanisms sometimes exhibit "mismatches" to the modern environment. One example is the fact that although about 10,000 people are killed with guns in the US annually, whereas spiders and snakes kill only a handful, people nonetheless learn to fear spiders and snakes about as easily as they do a pointed gun, and more easily than an unpointed gun, rabbits or flowers. A potential explanation is that spiders and snakes were a threat to human ancestors throughout the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

, whereas guns (and rabbits and flowers) were not. There is thus a mismatch between our evolved fear-learning psychology and the modern environment.

This mismatch also shows up in the phenomena of the supernormal stimulus, a stimulus that elicits a response more strongly than the stimulus for which the response evolved. The term was coined by Niko Tinbergen to describe animal behavior, but psychologist Deirdre Barrett
Deirdre Barrett
Deirdre Barrett, Ph.D. is an author and psychologist who teaches at Harvard Medical School. She is known for her research on dreams, hypnosis, and imagery and has written on evolutionary psychology. Barrett is a Past President of The International Association for the Study of Dreams and of the...

 said that supernormal stimulation governs the behavior of humans as powerfully as that of animals. She explained junk food as an exaggerated stimulus to cravings for salt, sugar, and fats, and she says that television is an exaggeration of social cues of laughter, smiling faces and attention-grabbing action. Magazine centerfolds and double cheeseburgers pull instincts intended for an EEA where breast development was a sign of health, youth and fertility in a prospective mate, and fat was a rare and vital nutrient.

Research methods


Evolutionary theory is heuristic
Heuristic
Heuristic refers to experience-based techniques for problem solving, learning, and discovery. Heuristic methods are used to speed up the process of finding a satisfactory solution, where an exhaustive search is impractical...

 in that it may generate hypotheses that might not be developed from other theoretical approaches. One of the major goals of adaptationist research is to identify which organismic traits are likely to be adaptations, and which are byproducts or random variations. As noted earlier, adaptations are expected to show evidence of complexity, functionality, and species universality, while byproducts or random variation will not. In addition, adaptations are expected to manifest as proximate mechanisms that interact with the environment in either a generally obligate or facultative fashion (see above). Evolutionary psychologists are also interested in identifying these proximate mechanisms (sometimes termed "mental mechanisms" or "psychological adaptations") and what type of information they take as input, how they process that information, and their outputs. Evolutionary developmental psychology
Evolutionary developmental psychology
Evolutionary developmental psychology, , is the application of the basic principles of Darwinian evolution, particularly natural selection, to explain contemporary human development...

, or "evo-devo," focuses on how adaptations may be activated at certain developmental times (e.g., losing baby teeth, adolescence, etc.) or how events during the development of an individual may alter life history
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...

 trajectories.

Evolutionary psychologists use several strategies to develop and test hypotheses about whether a psychological trait is likely to be an evolved adaptation. Buss (2011) notes that these methods include:
Cross-cultural Consistency. Characteristics that that been demonstrated to be cross cultural human universals
Human Universals
Human Universals is a book by Donald Brown, an American professor of anthropology who worked at the University of California, Santa Barbara. It was published by McGraw Hill in 1991...

 such as smiling, crying, facial expressions are presumed to be evolved psychological adaptations. Several evolutionary psychologists have collected massive datasets from cultures around the world to assess cross-cultural universalty.

Function to Form (or "problem to solution"). The fact that males, but not females, risk potential misidentification of genetic offspring (referred to as "paternity insecurity") led evolutionary psychologists to hypothesize that, compared to females, male jealousy would be more focused on sexual, rather than emotional, infidelity.

Form to Function (reverse-engineering -- or "solution to problem"). Morning sickness
Morning sickness
Morning sickness, also called nausea gravidarum, nausea, vomiting of pregnancy , or pregnancy sickness is a condition that affects more than half of all pregnant women. Related to increased oestrogen levels, a similar form of nausea is also seen in some women who use hormonal contraception or...

, and associated aversions to certain types of food, during pregnancy seemed to have the characteristics of an evolved adaptation (complexity and universality). Margie Profet
Margie Profet
Margie Profet is an American evolutionary biologist with no formal biology training who created a decade-long controversy when she published her findings on the role of Darwinian evolution in menstruation, allergies and morning sickness....

 hypothesized that the function was to avoid the ingestion of toxins during early pregnancy that could damage fetus (but which are likely harmless to healthy women).

Corresponding Neurological Modules Evolutionary psychology and cognitive neuropsychology are mutually compatible -- evolutionary psychology helps to identify psychological adaptations and their ultimate, evolutionary functions, while neuropsychology helps to identify the proximate manifestations of these adaptations.


Evolutionary psychologists also use various sources of data for testing, including experiments, archeological records, data from hunter-gatherer societies, observational studies, self-reports and surveys, public records, and human products.
Recently, additional methods and tools have been introduced based on fictional scenarios, mathematical models, and multi-agent computer simulations.

Major areas of research


Foundational areas of research in evolutionary psychology can be divided into broad categories of adaptive problems that arise from the theory of evolution itself: survival, mating, parenting, family and kinship, interactions with non-kin, and cultural evolution.

Survival and individual level psychological adaptations


Problems of survival are thus clear targets for the evolution of physical and psychological adaptations. Major problems our ancestors faced included food selection and acquisition; territory selection and physical shelter; and avoiding predators and other environmental threats.

Consciousness



Consciousness is likely an evolved adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

 since it meets George Williams
George C. Williams
Professor George Christopher Williams was an American evolutionary biologist.Williams was a professor emeritus of biology at the State University of New York at Stony Brook. He was best known for his vigorous critique of group selection. The work of Williams in this area, along with W. D...

' criteria of species universality, complexity, and functionality, and it is a trait that apparently increases fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

.

In his paper "Evolution of consciousness," John Eccles argues that special anatomical and physical adaptations of the mammalian cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

 gave rise to consciousness. In contrast, others have argued that the recursive circuitry underwriting consciousness is much more primitive, having evolved initially in pre-mammalian species because it improves the capacity for interaction with both social and natural environments by providing an energy-saving "neutral" gear in an otherwise energy-expensive motor output machine. Once in place, this recursive circuitry may well have provided a basis for the subsequent development of many of the functions that consciousness facilitates in higher organisms, as outlined by Bernard J. Baars. Richard Dawkins suggested that we evolved consciousness in order to make ourselves the subjects of thought. Daniel Povinelli suggests that large, tree-climbing apes evolved consciousness to take into account one's own mass when moving safely among tree branches. Consistent with this hypothesis, Gordon Gallup found that chimps and orangutans, but not little monkeys or terrestrial gorillas, demonstrated self-awareness in mirror tests.

The concept of consciousness can refer to voluntary action, awareness, or wakefulness. However, even voluntary behavior involves unconscious mechanisms.Many cognitive processes take place in the cognitive unconscious, unavailable to conscious awareness. Some behaviors are conscious when learned but then become unconscious, seemingly automatic. Learning, especially implicitly learning a skill, can take place outside of consciousness. For example, plenty of people know how to turn right when they ride a bike, but very few can accurately explain how they actually do so.

Evolutionary psychology (EP) is an approach in the social and natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...

s that examines psychological traits
Trait theory
In psychology, Trait theory is a major approach to the study of human personality. Trait theorists are primarily interested in the measurement of traits, which can be defined as habitual patterns of behavior, thought, and emotion. According to this perspective, traits are relatively stable over...

 such as memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

, perception
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...

, and language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

 from a modern evolutionary perspective
Modern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...

. It seeks to identify which human psychological traits are evolved adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s, that is, the functional products of natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 or sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

. Adaptationist thinking about physiological mechanisms, such as the heart, lungs, and immune system, is common in evolutionary biology. Evolutionary psychology applies the same thinking to psychology, arguing that the mind has a modular structure
Modularity of mind
Modularity of mind is the notion that a mind may, at least in part, be composed of separate innate structures which have established evolutionarily developed functional purposes...

 similar to that of the body, with different modular adaptations serving different functions. Evolutionary psychologists argue that much of human behavior is the output of psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s that evolved to solve recurrent problems in human ancestral environments.

The adaptationist approach is steadily increasing as an influence in the general field of psychology.

Evolutionary psychologists suggest that EP is not simply a subdiscipline of psychology but that evolutionary theory can provide a foundational, metatheoretical framework that integrates the entire field of psychology, in the same way it has for biology.

Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations including the abilities to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, and cooperate with others. They report successful tests of theoretical predictions related to such topics as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.

The theories and findings of EP have applications in many fields, including economics
Economics
Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...

, law
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

, psychiatry
Psychiatry
Psychiatry is the medical specialty devoted to the study and treatment of mental disorders. These mental disorders include various affective, behavioural, cognitive and perceptual abnormalities...

, politics
Politics
Politics is a process by which groups of people make collective decisions. The term is generally applied to the art or science of running governmental or state affairs, including behavior within civil governments, but also applies to institutions, fields, and special interest groups such as the...

, and literature
Literature
Literature is the art of written works, and is not bound to published sources...

.

Controversies concerning EP involve questions of testability, cognitive and evolutionary assumptions (such as modular functioning of the brain or the ancestral environment), importance of non-genetic and non-adaptive explanations, as well as political and ethical issues due to interpretations of research results.

Principles


Evolutionary psychology is an approach that views human nature
Human nature
Human nature refers to the distinguishing characteristics, including ways of thinking, feeling and acting, that humans tend to have naturally....

 as a universal set of evolved psychological adaptations to recurring problems in the ancestral environment. It refers to sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, a systematic study in biological basis in gender behaviour. Proponents of EP suggest that it seeks to heal a fundamental division at the very heart of science --- that between the soft human social sciences and the hard natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...

s, recognizing that human beings are living organisms, which motivates understanding psychology
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

 as a branch of biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

. Anthropologist John Tooby
John Tooby
John Tooby is an American anthropologist, who, together with psychologist wife Leda Cosmides, helped pioneer the field of evolutionary psychology....

 and psychologist Leda Cosmides
Leda Cosmides
Leda Cosmides, is an American psychologist, who, together with anthropologist husband John Tooby, helped develop the field of evolutionary psychology....

 note:

"Evolutionary psychology is the long-forestalled scientific attempt to assemble out of the disjointed, fragmentary, and mutually contradictory human disciplines a single, logically integrated research framework for the psychological, social, and behavioral sciences—a framework
that not only incorporates the evolutionary sciences on a full and equal basis, but that systematically works out all of the revisions in existing belief and research practice that such a synthesis requires."


Just as human physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

 and evolutionary physiology
Evolutionary physiology
Evolutionary physiology is the study of physiological evolution, which is to say, the manner in which the functional characteristics of individuals in a population of organisms have responded to selection across multiple generations during the history of the population.It is a subdiscipline of both...

 have worked to identify physical adaptations of the body that represent "human physiological nature," the purpose of evolutionary psychology is to identify evolved emotional and cognitive adaptations that represent "human psychological nature." EP is, to quote Steven Pinker
Steven Pinker
Steven Arthur Pinker is a Canadian-American experimental psychologist, cognitive scientist, linguist and popular science author...

, "not a single theory but a large set of hypotheses" and a term which "has also come to refer to a particular way of applying evolutionary theory to the mind, with an emphasis on adaptation, gene-level selection, and modularity
Modularity of mind
Modularity of mind is the notion that a mind may, at least in part, be composed of separate innate structures which have established evolutionarily developed functional purposes...

." Evolutionary psychology adopts an understanding of the mind that is based on the computational theory of mind
Computational theory of mind
In philosophy, the computational theory of mind is the view that the human mind is an information processing system and that thinking is a form of computing. The theory was proposed in its modern form by Hilary Putnam in 1961 and developed by Jerry Fodor in the 60s and 70s...

. It describes mental processes as computational operations, so that for example a fear response is described as arising from a neurological computation that inputs the perceptional data, e.g. a visual image of a spider and outputs the appropriate reaction, e.g. fear of possibly dangerous animals.

While philosophers have generally considered human mind to include broad faculties, such as reason and lust, evolutionary psychologists describe evolved psychological mechanisms as narrowly focused to deal with specific issues, such as catching cheaters or choosing mates. EP views the human brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

 as comprising many functional mechanisms, called psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s
or evolved cognitive mechanisms or cognitive modules, designed by the process of natural selection. Examples include language-acquisition modules
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...

, incest-avoidance mechanisms
Westermarck effect
The Westermarck effect, or reverse sexual imprinting, is a hypothetical psychological effect through which people who live in close domestic proximity during the first few years of their lives become desensitized to later sexual attraction. This phenomenon was first hypothesized by Finnish...

, cheater-detection mechanisms
Wason selection task
Devised in 1966 by Peter Cathcart Wason, the Wason selection task, one of the most famous tasks in the psychology of reasoning, is a logic puzzle which is formally equivalent to the following question:...

, intelligence and sex
Sex
In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

-specific mating preferences, foraging mechanisms, alliance-tracking mechanisms, agent-detection mechanisms, and others. Some mechanisms, termed domain-specific, deal with recurrent adaptive problems over the course of human evolutionary history. Domain-general mechanisms, on the other hand, are proposed to deal with evolutionary novelty.

EP has roots in cognitive psychology
Cognitive psychology
Cognitive psychology is a subdiscipline of psychology exploring internal mental processes.It is the study of how people perceive, remember, think, speak, and solve problems.Cognitive psychology differs from previous psychological approaches in two key ways....

 and evolutionary biology but also draws on behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

, artificial intelligence
Artificial intelligence
Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...

, genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

, ethology
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....

, anthropology
Anthropology
Anthropology is the study of humanity. It has origins in the humanities, the natural sciences, and the social sciences. The term "anthropology" is from the Greek anthrōpos , "man", understood to mean mankind or humanity, and -logia , "discourse" or "study", and was first used in 1501 by German...

, archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

, biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, and zoology
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

. EP is closely linked to sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, but there are key differences between them including the emphasis on domain-specific rather than domain-general mechanisms, the relevance of measures of current fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

, the importance of mismatch theory
Mismatch theory
Mismatch theory is a concept in evolutionary biology that refers to fluidity in fitness criteria.The essence of mismatch theory is that organisms possess traits that have been passed down through generations, preserved by natural selection because of their adaptive function in a given environment...

, and psychology rather than behaviour. Most of what is now labeled as sociobiological research is now confined to the field of behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

.

Nikolaas Tinbergen
Nikolaas Tinbergen
Nikolaas "Niko" Tinbergen was a Dutch ethologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning organization and elicitation of individual and social behaviour patterns in animals.In the 1960s he...

's four categories of questions
Tinbergen's four questions
Tinbergen's four questions, named after Nikolaas Tinbergen, are complementary categories of explanations for behavior. It suggests that an integrative understanding of behavior must include both a proximate and ultimate analysis of behavior, as well as an understanding of both...

 can help to clarify the distinctions between several different, but complementary, types of explanations. Evolutionary psychology focuses primarily on the "why?" questions, while traditional psychology focuses on the "how?" questions.
Sequential vs. Static Perspective
Historical/Developmental
Explanation of current form in terms of a historical sequence
Current Form
Explanation of the current form of species
How vs. Why Questions Proximate
How an individual organism's structures function
Ontogeny
Developmental explanations for changes in individuals, from DNA to their current form
Mechanism
Mechanistic explanations for how an organism's structures work
Evolutionary
Why a species evolved the structures (adaptations) it has
Phylogeny
The history of the evolution of sequential changes in a species over many generations
Adaptation
A species trait that evolved to solve a reproductive or survival problem in the ancestral environment

Premises


Evolutionary psychology is founded on several core premises.
  1. The brain is an information processing device, and it produces behavior in response to external and internal inputs.
  2. The brain's adaptive mechanisms were shaped by natural and sexual selection.
  3. Different neural mechanisms are specialized for solving problems in humanity's evolutionary past.
  4. The brain has evolved specialized neural mechanisms that were designed for solving problems that recurred over deep evolutionary time, giving modern humans Stone age minds.
  5. Most contents and processes of the brain are unconscious; and most mental problems that seem easy to solve are actually extremely difficult problems that are solved unconsciously by complicated neural mechanisms.
  6. Human psychology consists of many specialized mechanisms, each sensitive to different classes of information or inputs. These mechanisms combine to produce manifest behavior.

History



Evolutionary psychology has its historical roots in Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

’s theory of natural selection. In The Origin of Species Darwin predicted that psychology would develop an evolutionary basis:

Two of his later books were devoted to the study of animal emotions and psychology; The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex is a book on evolutionary theory by English naturalist Charles Darwin, first published in 1871. It was Darwin's second great book on evolutionary theory, following his 1859 work, On The Origin of Species. In The Descent of Man, Darwin applies...

in 1871 and The Expression of the Emotions in Man and Animals
The Expression of the Emotions in Man and Animals
The Expression of the Emotions in Man and Animals is a book by Charles Darwin, published in 1872, concerning genetically determined aspects of behaviour. It was published thirteen years after On The Origin of Species and is, along with his 1871 book The Descent of Man, Darwin's main consideration...

in 1872. Darwin's work inspired William James
William James
William James was a pioneering American psychologist and philosopher who was trained as a physician. He wrote influential books on the young science of psychology, educational psychology, psychology of religious experience and mysticism, and on the philosophy of pragmatism...

’s functionalist approach to psychology.

The content of EP has derived from, on the one hand, the biological sciences (especially evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary theory as it relates to ancient human environments, the study of paleoanthropology
Paleoanthropology
Paleoanthropology, which combines the disciplines of paleontology and physical anthropology, is the study of ancient humans as found in fossil hominid evidence such as petrifacted bones and footprints.-19th century:...

 and animal behavior) and, on the other, the human sciences especially psychology.

Evolutionary biology as an academic discipline
Academic discipline
An academic discipline, or field of study, is a branch of knowledge that is taught and researched at the college or university level. Disciplines are defined , and recognized by the academic journals in which research is published, and the learned societies and academic departments or faculties to...

 emerged with the modern evolutionary synthesis
Modern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...

 in the 1930s and 1940s. In the 1930s the study of animal behaviour (ethology
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....

) emerged with the work of Dutch biologist Nikolaas Tinbergen
Nikolaas Tinbergen
Nikolaas "Niko" Tinbergen was a Dutch ethologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning organization and elicitation of individual and social behaviour patterns in animals.In the 1960s he...

 and Austrian biologists Konrad Lorenz
Konrad Lorenz
Konrad Zacharias Lorenz was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize with Nikolaas Tinbergen and Karl von Frisch...

  and Karl von Frisch
Karl von Frisch
Karl Ritter von Frisch was an Austrian ethologist who received the Nobel Prize in Physiology or Medicine in 1973, along with Nikolaas Tinbergen and Konrad Lorenz....

.

W.D. Hamilton's (1964) papers on inclusive fitness
Inclusive fitness
In evolutionary biology and evolutionary psychology, the inclusive fitness of an organism is the sum of its classical fitness and the number of equivalents of its own offspring it can add to the population by supporting others...

 and Robert Trivers
Robert Trivers
Robert L. Trivers is an American evolutionary biologist and sociobiologist and Professor of Anthropology and Biological Sciences at Rutgers University. Trivers is most noted for proposing the theories of reciprocal altruism , parental investment , facultative sex ratio determination , and...

's (1972) theories on reciprocity
Reciprocity (evolution)
Reciprocity in evolutionary biology refers to mechanisms whereby the evolution of cooperative or altruistic behaviour may be favoured by the probability of future mutual interactions...

 and parental investment
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

 helped to establish evolutionary thinking in psychology and the other social sciences. In 1975, E O Wilson combined evolutionary theory with studies of animal and social behavior, building on the works of Lorenz and Tinbergen, in his book Sociobiology:The New Synthesis.

In the 1970s, two major branches developed from ethology. Firstly, the study of animal social behavior (including humans) generated sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, defined by its pre-eminent proponent Edward O. Wilson in 1975 as "the systematic study of the biological basis of all social behavior" and in 1978 as "the extension of population biology and evolutionary theory to social organization". Secondly, there was behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

 which placed less emphasis on social behavior by focusing on the ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

  and evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary basis of both animal and human
Human behavioral ecology
Human behavioral ecology or human evolutionary ecology applies the principles of evolutionary theory and optimization to the study of human behavioral and cultural diversity. HBE examines the adaptive design of traits, behaviors, and life histories of humans in an ecological context...

 behavior.

In the 1970s and 1980s university departments began to include the term evolutionary biology in their titles. The modern era of evolutionary psychology was ushered in, in particular, by Donald Symons
Donald Symons
Donald Symons is an American anthropologist who is best known as one of the founders of evolutionary psychology, and for pioneering the study of human sexuality from an evolutionary perspective...

' 1979 book The Evolution Human Sexuality and Tooby and Cosmides 1992 book The Adapted Mind
The Adapted Mind
The Adapted Mind: Evolutionary Psychology and the Generation of Culture is an edited volume, first published in 1992 by Oxford University Press, edited by Jerome Barkow, Leda Cosmides and John Tooby...

.

From psychology there are the primary streams of developmental
Developmental psychology
Developmental psychology, also known as human development, is the scientific study of systematic psychological changes, emotional changes, and perception changes that occur in human beings over the course of their life span. Originally concerned with infants and children, the field has expanded to...

, social
Social psychology
Social psychology is the scientific study of how people's thoughts, feelings, and behaviors are influenced by the actual, imagined, or implied presence of others. By this definition, scientific refers to the empirical method of investigation. The terms thoughts, feelings, and behaviors include all...

 and cognitive psychology
Cognitive psychology
Cognitive psychology is a subdiscipline of psychology exploring internal mental processes.It is the study of how people perceive, remember, think, speak, and solve problems.Cognitive psychology differs from previous psychological approaches in two key ways....

. Establishing some measure of the relative influence of genetics and environment on behavior has been at the core of behavioral genetics and its variants, notably studies at the molecular level that examine the relationship between genes, neurotransmitters and behavior. Dual inheritance theory
Dual inheritance theory
Dual inheritance theory , also known as gene-culture coevolution, was developed in the late 1970s and early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution...

 (DIT), developed in the late 1970s and early 1980s, has a slightly different perspective by trying to explain how human behavior
Human behavior
Human behavior refers to the range of behaviors exhibited by humans and which are influenced by culture, attitudes, emotions, values, ethics, authority, rapport, hypnosis, persuasion, coercion and/or genetics....

 is a product of two different and interacting evolutionary processes: genetic evolution  and cultural evolution. DIT is a "middle-ground" between much of social science, which views culture
Culture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...

  as the primary cause of human behavioral variation, and human sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

  and evolutionary psychology which view culture as an insignificant by-product of genetic selection.

Theoretical foundations


The theories on which evolutionary psychology is based originated with Charles Darwin's work, including his speculations about the evolutionary origins of social instincts in humans. Modern evolutionary psychology, however, is possible only because of advances in evolutionary theory in the 20th century.

Evolutionary psychologists say that natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 has provided humans with many psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s, in much the same way that it generated humans' anatomical and physiological adaptations. As with adaptations in general, psychological adaptations are said to be specialized for the environment in which an organism evolved, the environment of evolutionary adaptedness, or EEA. Sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

 provides organisms with adaptations related to mating. For male mammals, which have a relatively fast reproduction rate, sexual selection leads to adaptations that help them compete for females. For female mammals, with a relatively slow reproduction rate, sexual selection leads to choosiness, which helps females select higher quality mates. Charles Darwin described both natural selection and sexual selection, but he relied on group selection to explain the evolution of self-sacrificing behavior. Group selection is a weak explanation because in any group the less self-sacrificing animals will be more likely to survive and the group will become less self-sacrificing.

In 1964, William D. Hamilton proposed inclusive fitness
Inclusive fitness
In evolutionary biology and evolutionary psychology, the inclusive fitness of an organism is the sum of its classical fitness and the number of equivalents of its own offspring it can add to the population by supporting others...

 theory, emphasizing a "gene's-eye
Gene-centered view of evolution
The gene-centered view of evolution, gene selection theory or selfish gene theory holds that evolution occurs through the differential survival of competing genes, increasing the frequency of those alleles whose phenotypic effects successfully promote their own propagation, with gene defined as...

" view of evolution. Hamilton noted that individuals can increase the replication of their genes into the next generation by helping close relatives with whom they share genes survive and reproduce. According to "Hamilton's rule", a self-sacrificing behavior can evolve if it helps close relatives so much that it more than compensates for the individual animal's sacrifice. Inclusive fitness theory resolved the issue of how "altruism" evolved. Other theories also help explain the evolution of altruistic behavior, including evolutionary game theory
Evolutionary game theory
Evolutionary game theory is the application of Game Theory to evolving populations of lifeforms in biology. EGT is useful in this context by defining a framework of contests, strategies and analytics into which Darwinian competition can be modelled. It originated in 1973 with John Maynard Smith...

, tit-for-tat reciprocity, and generalized reciprocity. These theories not only help explain the development of altruistic behavior but also account for hostility toward cheaters (individuals that take advantage of others' altruism).

Several mid-level evolutionary theories inform evolutionary psychology. The r/K selection theory proposes that some species prosper by having many offspring while others follow the strategy of having fewer offspring but investing much more in each one. Humans follow the second strategy. Parental investment
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

 theory explains how parents invest more or less in individual offspring based on how successful those offspring are likely to be, and thus how much they might improve the parents' inclusive fitness. According to the Trivers-Willard hypothesis
Trivers-Willard hypothesis
In evolutionary biology, the Trivers–Willard hypothesis, formally proposed by Robert Trivers and Dan Willard, predicts greater investment in males by parents in good conditions and greater investment in females by parents in poor conditions...

, parents in good conditions tend to invest more in sons (who are best able to take advantage of good conditions), while parents in poor conditions tend to invest more in daughters (who are best able to have successful offspring even in poor conditions). According to life history theory
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...

, animals evolve life histories to match their environments, determining details such as age at first reproduction and number of offspring. Dual inheritance theory
Dual inheritance theory
Dual inheritance theory , also known as gene-culture coevolution, was developed in the late 1970s and early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution...

 posits that genes and human culture have interacted, with genes affecting the development of culture and culture, in turn, affecting human evolution on a genetic level (see also the Baldwin effect
Baldwin effect
The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is a theory of a possible evolutionary processes that was originally put forward in 1896 in a paper, "A New Factor in Evolution," by American psychologist James Mark Baldwin. The paper proposed a mechanism for specific...

).

Evolved psychological mechanisms



Evolutionary psychology is based on the hypothesis that, just like hearts, lungs, livers, kidneys, and immune systems, cognition has functional structure that has a genetic basis, and therefore has evolved by natural selection. Like other organs and tissues, this functional structure should be universally shared amongst a species, and should solve important problems of survival and reproduction.

Evolutionary psychologists seek to understand psychological mechanisms
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

 by understanding the survival and reproductive functions they might have served over the course of evolutionary history. These might include abilities to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, cooperate with others. Consistent with the theory of natural selection, evolutionary psychology sees humans as often in conflict with others, including mates and relatives. Even mothers sometimes struggle with their children over weaning, which benefits the mother more than the child. Evolutionary psychology also recognizes the role of kin selection and reciprocity in evolving prosocial traits such as altruism. Like chimps and bonobos, humans have subtle and flexible social instincts, allowing them to form extended families, lifelong friendships, and political alliances. In studies testing theoretical predictions, evolutionary psychologists have made modest findings on topics such as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.

Products of evolution: adaptations, exaptations, byproducts, and random variation


Not all traits of organisms are adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s. As noted in the table below, traits may also be exaptation
Exaptation
Exaptation, cooption, and preadaptation are related terms referring to shifts in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another. Exaptations are common in both anatomy and behaviour...

s, byproducts of adaptations (sometimes called "spandrels"), or random variation between individuals.

Psychological adaptations are hypothesized to be innate or relatively easy to learn, and to manifest in cultures worldwide. For example, the ability of toddlers to learn a language with virtually no training is likely to be a psychological adaptation. On the other hand, ancestral humans did not read or write, thus today learning to read and write require extensive training, and presumably represent byproducts of cognitive processing that use psychological adaptations designed for other functions.
Adaptation Exaptation By-Product Random Noise
Definition Organismic trait designed to solve an ancestral problem(s). Shows complexity, special "design", functionality Adaptation that has been "re-designed" to solve a different adaptive problem. Byproduct of an adapative mechanism with no current or ancestral function Random variations in an adaptation or byproduct
Physiological Example Bones / Umbilical cord Small bones of the inner ear White color of bones / Belly button Bumps on the skull, convex or concave belly button shape
Psychological Example Toddlers’ ability to learn to talk with minimal instruction. Voluntary Attention Ability to learn to read and write. Within-sex variations in voice pitch.


One of the tasks of evolutionary psychology is to identify which psychological traits are likely to be adaptations, byproducts or random variation. George C Williams suggested that an "adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

 is a special and onerous concept that should only be used where it is really necessary". As noted by Williams and others, adaptations can be identified by their improbable complexity, species universality, and adaptive functionality.

Obligate and facultative adaptations


A question that may be asked about an adaptation is whether it is generally obligate (relatively robust in the face of typical environmental variation) or facultative (sensitive to typical environmental variation). The sweet taste of sugar and the pain of hitting one's knee against concrete are the result of fairly obligate psychological adaptations; typical environmental variability during development does not much affect their operation. By contrast, facultative adaptations are somewhat like "if-then" statements. For example, adult attachment style seems particularly sensitive to early childhood experiences. As adults, the propensity to develop close, trusting bonds with others is dependent on whether early childhood caregivers could be trusted to provide reliable assistance and attention. The adaptation for skin to tan is conditional to exposure to sunlight; this is an example of another facultative adaptation. When a psychological adaptation is facultative, evolutionary psychologists concern themselves with how developmental and environmental inputs influence the expression of the adaptation.

Cultural universals



Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations. Cultural universals include behaviors related to language, cognition, social roles, gender roles, and technology. Evolved psychological adaptations (such as the ability to learn a language) interact with cultural inputs to produce specific behaviors (e.g., the specific language learned). Basic gender differences, such as greater eagerness for sex among men and greater coyness among women, are explained as sexually dimorphic psychological adaptations that reflect the different reproductive strategies of males and females. Evolutionary psychologists contrast their approach to what they term the "standard social science model
Standard social science model
The term the Standard Social Science Model was first introduced to a wide audience by John Tooby and Leda Cosmides in the 1992 edited volume The Adapted Mind, to describe the "blank slate," social constructionist,or "cultural determinist" perspective that they claim is the dominant theoretical...

," according to which the mind is a general-purpose cognition device shaped almost entirely by culture.

Environment of evolutionary adaptedness



EP argues that to properly understand the functions of the brain, one must understand the properties of the environment in which the brain evolved. That environment is often referred to as the "environment of evolutionary adaptedness" (EEA).

The term "environment of evolutionary adaptedness" was coined by John Bowlby
John Bowlby
Edward John Mostyn "John" Bowlby was a British psychologist, psychiatrist and psychoanalyst, notable for his interest in child development and for his pioneering work in attachment theory.- Family background :...

 as part of attachment theory
Attachment theory
Attachment theory describes the dynamics of long-term relationships between humans. Its most important tenet is that an infant needs to develop a relationship with at least one primary caregiver for social and emotional development to occur normally. Attachment theory is an interdisciplinary study...

. It refers to the environment to which a particular evolved mechanism is adapted. More specifically, the EEA is defined as the set of historically recurring selection pressures that formed a given adaptation, as well as those aspects of the environment that were necessary for the proper development and functioning of the adaptation.

Humans, comprising the genus Homo
Homo (genus)
Homo is the genus that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis....

, appeared between 1.5 and 2.5 million years ago, a time that roughly coincides with the start of the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 1.8 million years ago. Because the Pleistocene ended a mere 12,000 years ago, most human adaptations either newly evolved during the Pleistocene, or were maintained by stabilizing selection
Stabilizing selection
-Description:Stabilizing or ambidirectional selection, , is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. This is probably the most common mechanism of action for natural selection...

 during the Pleistocene. Evolutionary psychology therefore proposes that the majority of human psychological mechanisms are adapted to reproductive problems frequently encountered in Pleistocene environments. In broad terms, these problems include those of growth, development, differentiation, maintenance, mating, parenting, and social relationships.

The EEA is significantly different from modern society. Our ancestors lived in smaller groups, had more cohesive cultures, and had more stable and rich contexts for identity and meaning. Researchers look to existing hunter-gatherer societies for clues as to how our hunter-gatherer ancestors lived. Since hunter-gatherer societies are egalitarian, the ancestral population may have been egalitarian as well, a social pattern different from the hierarchies found in chimp bands. Unfortunately, the few surviving hunter-gatherer societies are different from each other, and they have been pushed out of the best land and into harsh environments, so it is not clear how closely they reflect ancestral culture.

Evolutionary psychologists sometimes look to chimpanzees, bonobos, and other great apes for insight into human ancestral behavior. Christopher Ryan and Cacilda Jetha argue that evolutionary psychologists have overemphasized our similarity to chimps, which are more violent, while underestimating our similarity to bonobos, which are more peaceful.

Mismatches


Since an organism's adaptations were suited to its ancestral environment, a new and different environment can create a mismatch. Because humans are mostly adapted to Pleistocene environments, psychological mechanisms sometimes exhibit "mismatches" to the modern environment. One example is the fact that although about 10,000 people are killed with guns in the US annually, whereas spiders and snakes kill only a handful, people nonetheless learn to fear spiders and snakes about as easily as they do a pointed gun, and more easily than an unpointed gun, rabbits or flowers. A potential explanation is that spiders and snakes were a threat to human ancestors throughout the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

, whereas guns (and rabbits and flowers) were not. There is thus a mismatch between our evolved fear-learning psychology and the modern environment.

This mismatch also shows up in the phenomena of the supernormal stimulus, a stimulus that elicits a response more strongly than the stimulus for which the response evolved. The term was coined by Niko Tinbergen to describe animal behavior, but psychologist Deirdre Barrett
Deirdre Barrett
Deirdre Barrett, Ph.D. is an author and psychologist who teaches at Harvard Medical School. She is known for her research on dreams, hypnosis, and imagery and has written on evolutionary psychology. Barrett is a Past President of The International Association for the Study of Dreams and of the...

 said that supernormal stimulation governs the behavior of humans as powerfully as that of animals. She explained junk food as an exaggerated stimulus to cravings for salt, sugar, and fats, and she says that television is an exaggeration of social cues of laughter, smiling faces and attention-grabbing action. Magazine centerfolds and double cheeseburgers pull instincts intended for an EEA where breast development was a sign of health, youth and fertility in a prospective mate, and fat was a rare and vital nutrient.

Research methods


Evolutionary theory is heuristic
Heuristic
Heuristic refers to experience-based techniques for problem solving, learning, and discovery. Heuristic methods are used to speed up the process of finding a satisfactory solution, where an exhaustive search is impractical...

 in that it may generate hypotheses that might not be developed from other theoretical approaches. One of the major goals of adaptationist research is to identify which organismic traits are likely to be adaptations, and which are byproducts or random variations. As noted earlier, adaptations are expected to show evidence of complexity, functionality, and species universality, while byproducts or random variation will not. In addition, adaptations are expected to manifest as proximate mechanisms that interact with the environment in either a generally obligate or facultative fashion (see above). Evolutionary psychologists are also interested in identifying these proximate mechanisms (sometimes termed "mental mechanisms" or "psychological adaptations") and what type of information they take as input, how they process that information, and their outputs. Evolutionary developmental psychology
Evolutionary developmental psychology
Evolutionary developmental psychology, , is the application of the basic principles of Darwinian evolution, particularly natural selection, to explain contemporary human development...

, or "evo-devo," focuses on how adaptations may be activated at certain developmental times (e.g., losing baby teeth, adolescence, etc.) or how events during the development of an individual may alter life history
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...

 trajectories.

Evolutionary psychologists use several strategies to develop and test hypotheses about whether a psychological trait is likely to be an evolved adaptation. Buss (2011) notes that these methods include:
Cross-cultural Consistency. Characteristics that that been demonstrated to be cross cultural human universals
Human Universals
Human Universals is a book by Donald Brown, an American professor of anthropology who worked at the University of California, Santa Barbara. It was published by McGraw Hill in 1991...

 such as smiling, crying, facial expressions are presumed to be evolved psychological adaptations. Several evolutionary psychologists have collected massive datasets from cultures around the world to assess cross-cultural universalty.

Function to Form (or "problem to solution"). The fact that males, but not females, risk potential misidentification of genetic offspring (referred to as "paternity insecurity") led evolutionary psychologists to hypothesize that, compared to females, male jealousy would be more focused on sexual, rather than emotional, infidelity.

Form to Function (reverse-engineering -- or "solution to problem"). Morning sickness
Morning sickness
Morning sickness, also called nausea gravidarum, nausea, vomiting of pregnancy , or pregnancy sickness is a condition that affects more than half of all pregnant women. Related to increased oestrogen levels, a similar form of nausea is also seen in some women who use hormonal contraception or...

, and associated aversions to certain types of food, during pregnancy seemed to have the characteristics of an evolved adaptation (complexity and universality). Margie Profet
Margie Profet
Margie Profet is an American evolutionary biologist with no formal biology training who created a decade-long controversy when she published her findings on the role of Darwinian evolution in menstruation, allergies and morning sickness....

 hypothesized that the function was to avoid the ingestion of toxins during early pregnancy that could damage fetus (but which are likely harmless to healthy women).

Corresponding Neurological Modules Evolutionary psychology and cognitive neuropsychology are mutually compatible -- evolutionary psychology helps to identify psychological adaptations and their ultimate, evolutionary functions, while neuropsychology helps to identify the proximate manifestations of these adaptations.


Evolutionary psychologists also use various sources of data for testing, including experiments, archeological records, data from hunter-gatherer societies, observational studies, self-reports and surveys, public records, and human products.
Recently, additional methods and tools have been introduced based on fictional scenarios, mathematical models, and multi-agent computer simulations.

Major areas of research


Foundational areas of research in evolutionary psychology can be divided into broad categories of adaptive problems that arise from the theory of evolution itself: survival, mating, parenting, family and kinship, interactions with non-kin, and cultural evolution.

Survival and individual level psychological adaptations


Problems of survival are thus clear targets for the evolution of physical and psychological adaptations. Major problems our ancestors faced included food selection and acquisition; territory selection and physical shelter; and avoiding predators and other environmental threats.

Consciousness



Consciousness is likely an evolved adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

 since it meets George Williams
George C. Williams
Professor George Christopher Williams was an American evolutionary biologist.Williams was a professor emeritus of biology at the State University of New York at Stony Brook. He was best known for his vigorous critique of group selection. The work of Williams in this area, along with W. D...

' criteria of species universality, complexity, and functionality, and it is a trait that apparently increases fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

.

In his paper "Evolution of consciousness," John Eccles argues that special anatomical and physical adaptations of the mammalian cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

 gave rise to consciousness. In contrast, others have argued that the recursive circuitry underwriting consciousness is much more primitive, having evolved initially in pre-mammalian species because it improves the capacity for interaction with both social and natural environments by providing an energy-saving "neutral" gear in an otherwise energy-expensive motor output machine. Once in place, this recursive circuitry may well have provided a basis for the subsequent development of many of the functions that consciousness facilitates in higher organisms, as outlined by Bernard J. Baars. Richard Dawkins suggested that we evolved consciousness in order to make ourselves the subjects of thought. Daniel Povinelli suggests that large, tree-climbing apes evolved consciousness to take into account one's own mass when moving safely among tree branches. Consistent with this hypothesis, Gordon Gallup found that chimps and orangutans, but not little monkeys or terrestrial gorillas, demonstrated self-awareness in mirror tests.

The concept of consciousness can refer to voluntary action, awareness, or wakefulness. However, even voluntary behavior involves unconscious mechanisms.Many cognitive processes take place in the cognitive unconscious, unavailable to conscious awareness. Some behaviors are conscious when learned but then become unconscious, seemingly automatic. Learning, especially implicitly learning a skill, can take place outside of consciousness. For example, plenty of people know how to turn right when they ride a bike, but very few can accurately explain how they actually do so.

Evolutionary psychology (EP) is an approach in the social and natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...

s that examines psychological traits
Trait theory
In psychology, Trait theory is a major approach to the study of human personality. Trait theorists are primarily interested in the measurement of traits, which can be defined as habitual patterns of behavior, thought, and emotion. According to this perspective, traits are relatively stable over...

 such as memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

, perception
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...

, and language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

 from a modern evolutionary perspective
Modern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...

. It seeks to identify which human psychological traits are evolved adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s, that is, the functional products of natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 or sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

. Adaptationist thinking about physiological mechanisms, such as the heart, lungs, and immune system, is common in evolutionary biology. Evolutionary psychology applies the same thinking to psychology, arguing that the mind has a modular structure
Modularity of mind
Modularity of mind is the notion that a mind may, at least in part, be composed of separate innate structures which have established evolutionarily developed functional purposes...

 similar to that of the body, with different modular adaptations serving different functions. Evolutionary psychologists argue that much of human behavior is the output of psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s that evolved to solve recurrent problems in human ancestral environments.

The adaptationist approach is steadily increasing as an influence in the general field of psychology.

Evolutionary psychologists suggest that EP is not simply a subdiscipline of psychology but that evolutionary theory can provide a foundational, metatheoretical framework that integrates the entire field of psychology, in the same way it has for biology.

Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations including the abilities to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, and cooperate with others. They report successful tests of theoretical predictions related to such topics as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.

The theories and findings of EP have applications in many fields, including economics
Economics
Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...

, law
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

, psychiatry
Psychiatry
Psychiatry is the medical specialty devoted to the study and treatment of mental disorders. These mental disorders include various affective, behavioural, cognitive and perceptual abnormalities...

, politics
Politics
Politics is a process by which groups of people make collective decisions. The term is generally applied to the art or science of running governmental or state affairs, including behavior within civil governments, but also applies to institutions, fields, and special interest groups such as the...

, and literature
Literature
Literature is the art of written works, and is not bound to published sources...

.

Controversies concerning EP involve questions of testability, cognitive and evolutionary assumptions (such as modular functioning of the brain or the ancestral environment), importance of non-genetic and non-adaptive explanations, as well as political and ethical issues due to interpretations of research results.

Principles


Evolutionary psychology is an approach that views human nature
Human nature
Human nature refers to the distinguishing characteristics, including ways of thinking, feeling and acting, that humans tend to have naturally....

 as a universal set of evolved psychological adaptations to recurring problems in the ancestral environment. It refers to sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, a systematic study in biological basis in gender behaviour. Proponents of EP suggest that it seeks to heal a fundamental division at the very heart of science --- that between the soft human social sciences and the hard natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...

s, recognizing that human beings are living organisms, which motivates understanding psychology
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

 as a branch of biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

. Anthropologist John Tooby
John Tooby
John Tooby is an American anthropologist, who, together with psychologist wife Leda Cosmides, helped pioneer the field of evolutionary psychology....

 and psychologist Leda Cosmides
Leda Cosmides
Leda Cosmides, is an American psychologist, who, together with anthropologist husband John Tooby, helped develop the field of evolutionary psychology....

 note:

"Evolutionary psychology is the long-forestalled scientific attempt to assemble out of the disjointed, fragmentary, and mutually contradictory human disciplines a single, logically integrated research framework for the psychological, social, and behavioral sciences—a framework
that not only incorporates the evolutionary sciences on a full and equal basis, but that systematically works out all of the revisions in existing belief and research practice that such a synthesis requires."


Just as human physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

 and evolutionary physiology
Evolutionary physiology
Evolutionary physiology is the study of physiological evolution, which is to say, the manner in which the functional characteristics of individuals in a population of organisms have responded to selection across multiple generations during the history of the population.It is a subdiscipline of both...

 have worked to identify physical adaptations of the body that represent "human physiological nature," the purpose of evolutionary psychology is to identify evolved emotional and cognitive adaptations that represent "human psychological nature." EP is, to quote Steven Pinker
Steven Pinker
Steven Arthur Pinker is a Canadian-American experimental psychologist, cognitive scientist, linguist and popular science author...

, "not a single theory but a large set of hypotheses" and a term which "has also come to refer to a particular way of applying evolutionary theory to the mind, with an emphasis on adaptation, gene-level selection, and modularity
Modularity of mind
Modularity of mind is the notion that a mind may, at least in part, be composed of separate innate structures which have established evolutionarily developed functional purposes...

." Evolutionary psychology adopts an understanding of the mind that is based on the computational theory of mind
Computational theory of mind
In philosophy, the computational theory of mind is the view that the human mind is an information processing system and that thinking is a form of computing. The theory was proposed in its modern form by Hilary Putnam in 1961 and developed by Jerry Fodor in the 60s and 70s...

. It describes mental processes as computational operations, so that for example a fear response is described as arising from a neurological computation that inputs the perceptional data, e.g. a visual image of a spider and outputs the appropriate reaction, e.g. fear of possibly dangerous animals.

While philosophers have generally considered human mind to include broad faculties, such as reason and lust, evolutionary psychologists describe evolved psychological mechanisms as narrowly focused to deal with specific issues, such as catching cheaters or choosing mates. EP views the human brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

 as comprising many functional mechanisms, called psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s
or evolved cognitive mechanisms or cognitive modules, designed by the process of natural selection. Examples include language-acquisition modules
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive, produce and use words to understand and communicate. This capacity involves the picking up of diverse capacities including syntax, phonetics, and an extensive vocabulary. This language might be vocal as with...

, incest-avoidance mechanisms
Westermarck effect
The Westermarck effect, or reverse sexual imprinting, is a hypothetical psychological effect through which people who live in close domestic proximity during the first few years of their lives become desensitized to later sexual attraction. This phenomenon was first hypothesized by Finnish...

, cheater-detection mechanisms
Wason selection task
Devised in 1966 by Peter Cathcart Wason, the Wason selection task, one of the most famous tasks in the psychology of reasoning, is a logic puzzle which is formally equivalent to the following question:...

, intelligence and sex
Sex
In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

-specific mating preferences, foraging mechanisms, alliance-tracking mechanisms, agent-detection mechanisms, and others. Some mechanisms, termed domain-specific, deal with recurrent adaptive problems over the course of human evolutionary history. Domain-general mechanisms, on the other hand, are proposed to deal with evolutionary novelty.

EP has roots in cognitive psychology
Cognitive psychology
Cognitive psychology is a subdiscipline of psychology exploring internal mental processes.It is the study of how people perceive, remember, think, speak, and solve problems.Cognitive psychology differs from previous psychological approaches in two key ways....

 and evolutionary biology but also draws on behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

, artificial intelligence
Artificial intelligence
Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...

, genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

, ethology
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....

, anthropology
Anthropology
Anthropology is the study of humanity. It has origins in the humanities, the natural sciences, and the social sciences. The term "anthropology" is from the Greek anthrōpos , "man", understood to mean mankind or humanity, and -logia , "discourse" or "study", and was first used in 1501 by German...

, archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

, biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, and zoology
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

. EP is closely linked to sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, but there are key differences between them including the emphasis on domain-specific rather than domain-general mechanisms, the relevance of measures of current fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

, the importance of mismatch theory
Mismatch theory
Mismatch theory is a concept in evolutionary biology that refers to fluidity in fitness criteria.The essence of mismatch theory is that organisms possess traits that have been passed down through generations, preserved by natural selection because of their adaptive function in a given environment...

, and psychology rather than behaviour. Most of what is now labeled as sociobiological research is now confined to the field of behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

.

Nikolaas Tinbergen
Nikolaas Tinbergen
Nikolaas "Niko" Tinbergen was a Dutch ethologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning organization and elicitation of individual and social behaviour patterns in animals.In the 1960s he...

's four categories of questions
Tinbergen's four questions
Tinbergen's four questions, named after Nikolaas Tinbergen, are complementary categories of explanations for behavior. It suggests that an integrative understanding of behavior must include both a proximate and ultimate analysis of behavior, as well as an understanding of both...

 can help to clarify the distinctions between several different, but complementary, types of explanations. Evolutionary psychology focuses primarily on the "why?" questions, while traditional psychology focuses on the "how?" questions.
Sequential vs. Static Perspective
Historical/Developmental
Explanation of current form in terms of a historical sequence
Current Form
Explanation of the current form of species
How vs. Why Questions Proximate
How an individual organism's structures function
Ontogeny
Developmental explanations for changes in individuals, from DNA to their current form
Mechanism
Mechanistic explanations for how an organism's structures work
Evolutionary
Why a species evolved the structures (adaptations) it has
Phylogeny
The history of the evolution of sequential changes in a species over many generations
Adaptation
A species trait that evolved to solve a reproductive or survival problem in the ancestral environment

Premises


Evolutionary psychology is founded on several core premises.
  1. The brain is an information processing device, and it produces behavior in response to external and internal inputs.
  2. The brain's adaptive mechanisms were shaped by natural and sexual selection.
  3. Different neural mechanisms are specialized for solving problems in humanity's evolutionary past.
  4. The brain has evolved specialized neural mechanisms that were designed for solving problems that recurred over deep evolutionary time, giving modern humans Stone age minds.
  5. Most contents and processes of the brain are unconscious; and most mental problems that seem easy to solve are actually extremely difficult problems that are solved unconsciously by complicated neural mechanisms.
  6. Human psychology consists of many specialized mechanisms, each sensitive to different classes of information or inputs. These mechanisms combine to produce manifest behavior.

History



Evolutionary psychology has its historical roots in Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

’s theory of natural selection. In The Origin of Species Darwin predicted that psychology would develop an evolutionary basis:

Two of his later books were devoted to the study of animal emotions and psychology; The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex is a book on evolutionary theory by English naturalist Charles Darwin, first published in 1871. It was Darwin's second great book on evolutionary theory, following his 1859 work, On The Origin of Species. In The Descent of Man, Darwin applies...

in 1871 and The Expression of the Emotions in Man and Animals
The Expression of the Emotions in Man and Animals
The Expression of the Emotions in Man and Animals is a book by Charles Darwin, published in 1872, concerning genetically determined aspects of behaviour. It was published thirteen years after On The Origin of Species and is, along with his 1871 book The Descent of Man, Darwin's main consideration...

in 1872. Darwin's work inspired William James
William James
William James was a pioneering American psychologist and philosopher who was trained as a physician. He wrote influential books on the young science of psychology, educational psychology, psychology of religious experience and mysticism, and on the philosophy of pragmatism...

’s functionalist approach to psychology.

The content of EP has derived from, on the one hand, the biological sciences (especially evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary theory as it relates to ancient human environments, the study of paleoanthropology
Paleoanthropology
Paleoanthropology, which combines the disciplines of paleontology and physical anthropology, is the study of ancient humans as found in fossil hominid evidence such as petrifacted bones and footprints.-19th century:...

 and animal behavior) and, on the other, the human sciences especially psychology.

Evolutionary biology as an academic discipline
Academic discipline
An academic discipline, or field of study, is a branch of knowledge that is taught and researched at the college or university level. Disciplines are defined , and recognized by the academic journals in which research is published, and the learned societies and academic departments or faculties to...

 emerged with the modern evolutionary synthesis
Modern evolutionary synthesis
The modern evolutionary synthesis is a union of ideas from several biological specialties which provides a widely accepted account of evolution...

 in the 1930s and 1940s. In the 1930s the study of animal behaviour (ethology
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....

) emerged with the work of Dutch biologist Nikolaas Tinbergen
Nikolaas Tinbergen
Nikolaas "Niko" Tinbergen was a Dutch ethologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning organization and elicitation of individual and social behaviour patterns in animals.In the 1960s he...

 and Austrian biologists Konrad Lorenz
Konrad Lorenz
Konrad Zacharias Lorenz was an Austrian zoologist, ethologist, and ornithologist. He shared the 1973 Nobel Prize with Nikolaas Tinbergen and Karl von Frisch...

  and Karl von Frisch
Karl von Frisch
Karl Ritter von Frisch was an Austrian ethologist who received the Nobel Prize in Physiology or Medicine in 1973, along with Nikolaas Tinbergen and Konrad Lorenz....

.

W.D. Hamilton's (1964) papers on inclusive fitness
Inclusive fitness
In evolutionary biology and evolutionary psychology, the inclusive fitness of an organism is the sum of its classical fitness and the number of equivalents of its own offspring it can add to the population by supporting others...

 and Robert Trivers
Robert Trivers
Robert L. Trivers is an American evolutionary biologist and sociobiologist and Professor of Anthropology and Biological Sciences at Rutgers University. Trivers is most noted for proposing the theories of reciprocal altruism , parental investment , facultative sex ratio determination , and...

's (1972) theories on reciprocity
Reciprocity (evolution)
Reciprocity in evolutionary biology refers to mechanisms whereby the evolution of cooperative or altruistic behaviour may be favoured by the probability of future mutual interactions...

 and parental investment
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

 helped to establish evolutionary thinking in psychology and the other social sciences. In 1975, E O Wilson combined evolutionary theory with studies of animal and social behavior, building on the works of Lorenz and Tinbergen, in his book Sociobiology:The New Synthesis.

In the 1970s, two major branches developed from ethology. Firstly, the study of animal social behavior (including humans) generated sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

, defined by its pre-eminent proponent Edward O. Wilson in 1975 as "the systematic study of the biological basis of all social behavior" and in 1978 as "the extension of population biology and evolutionary theory to social organization". Secondly, there was behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...

 which placed less emphasis on social behavior by focusing on the ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

  and evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary basis of both animal and human
Human behavioral ecology
Human behavioral ecology or human evolutionary ecology applies the principles of evolutionary theory and optimization to the study of human behavioral and cultural diversity. HBE examines the adaptive design of traits, behaviors, and life histories of humans in an ecological context...

 behavior.

In the 1970s and 1980s university departments began to include the term evolutionary biology in their titles. The modern era of evolutionary psychology was ushered in, in particular, by Donald Symons
Donald Symons
Donald Symons is an American anthropologist who is best known as one of the founders of evolutionary psychology, and for pioneering the study of human sexuality from an evolutionary perspective...

' 1979 book The Evolution Human Sexuality and Tooby and Cosmides 1992 book The Adapted Mind
The Adapted Mind
The Adapted Mind: Evolutionary Psychology and the Generation of Culture is an edited volume, first published in 1992 by Oxford University Press, edited by Jerome Barkow, Leda Cosmides and John Tooby...

.

From psychology there are the primary streams of developmental
Developmental psychology
Developmental psychology, also known as human development, is the scientific study of systematic psychological changes, emotional changes, and perception changes that occur in human beings over the course of their life span. Originally concerned with infants and children, the field has expanded to...

, social
Social psychology
Social psychology is the scientific study of how people's thoughts, feelings, and behaviors are influenced by the actual, imagined, or implied presence of others. By this definition, scientific refers to the empirical method of investigation. The terms thoughts, feelings, and behaviors include all...

 and cognitive psychology
Cognitive psychology
Cognitive psychology is a subdiscipline of psychology exploring internal mental processes.It is the study of how people perceive, remember, think, speak, and solve problems.Cognitive psychology differs from previous psychological approaches in two key ways....

. Establishing some measure of the relative influence of genetics and environment on behavior has been at the core of behavioral genetics and its variants, notably studies at the molecular level that examine the relationship between genes, neurotransmitters and behavior. Dual inheritance theory
Dual inheritance theory
Dual inheritance theory , also known as gene-culture coevolution, was developed in the late 1970s and early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution...

 (DIT), developed in the late 1970s and early 1980s, has a slightly different perspective by trying to explain how human behavior
Human behavior
Human behavior refers to the range of behaviors exhibited by humans and which are influenced by culture, attitudes, emotions, values, ethics, authority, rapport, hypnosis, persuasion, coercion and/or genetics....

 is a product of two different and interacting evolutionary processes: genetic evolution  and cultural evolution. DIT is a "middle-ground" between much of social science, which views culture
Culture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...

  as the primary cause of human behavioral variation, and human sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

  and evolutionary psychology which view culture as an insignificant by-product of genetic selection.

Theoretical foundations


The theories on which evolutionary psychology is based originated with Charles Darwin's work, including his speculations about the evolutionary origins of social instincts in humans. Modern evolutionary psychology, however, is possible only because of advances in evolutionary theory in the 20th century.

Evolutionary psychologists say that natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 has provided humans with many psychological adaptation
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

s, in much the same way that it generated humans' anatomical and physiological adaptations. As with adaptations in general, psychological adaptations are said to be specialized for the environment in which an organism evolved, the environment of evolutionary adaptedness, or EEA. Sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

 provides organisms with adaptations related to mating. For male mammals, which have a relatively fast reproduction rate, sexual selection leads to adaptations that help them compete for females. For female mammals, with a relatively slow reproduction rate, sexual selection leads to choosiness, which helps females select higher quality mates. Charles Darwin described both natural selection and sexual selection, but he relied on group selection to explain the evolution of self-sacrificing behavior. Group selection is a weak explanation because in any group the less self-sacrificing animals will be more likely to survive and the group will become less self-sacrificing.

In 1964, William D. Hamilton proposed inclusive fitness
Inclusive fitness
In evolutionary biology and evolutionary psychology, the inclusive fitness of an organism is the sum of its classical fitness and the number of equivalents of its own offspring it can add to the population by supporting others...

 theory, emphasizing a "gene's-eye
Gene-centered view of evolution
The gene-centered view of evolution, gene selection theory or selfish gene theory holds that evolution occurs through the differential survival of competing genes, increasing the frequency of those alleles whose phenotypic effects successfully promote their own propagation, with gene defined as...

" view of evolution. Hamilton noted that individuals can increase the replication of their genes into the next generation by helping close relatives with whom they share genes survive and reproduce. According to "Hamilton's rule", a self-sacrificing behavior can evolve if it helps close relatives so much that it more than compensates for the individual animal's sacrifice. Inclusive fitness theory resolved the issue of how "altruism" evolved. Other theories also help explain the evolution of altruistic behavior, including evolutionary game theory
Evolutionary game theory
Evolutionary game theory is the application of Game Theory to evolving populations of lifeforms in biology. EGT is useful in this context by defining a framework of contests, strategies and analytics into which Darwinian competition can be modelled. It originated in 1973 with John Maynard Smith...

, tit-for-tat reciprocity, and generalized reciprocity. These theories not only help explain the development of altruistic behavior but also account for hostility toward cheaters (individuals that take advantage of others' altruism).

Several mid-level evolutionary theories inform evolutionary psychology. The r/K selection theory proposes that some species prosper by having many offspring while others follow the strategy of having fewer offspring but investing much more in each one. Humans follow the second strategy. Parental investment
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

 theory explains how parents invest more or less in individual offspring based on how successful those offspring are likely to be, and thus how much they might improve the parents' inclusive fitness. According to the Trivers-Willard hypothesis
Trivers-Willard hypothesis
In evolutionary biology, the Trivers–Willard hypothesis, formally proposed by Robert Trivers and Dan Willard, predicts greater investment in males by parents in good conditions and greater investment in females by parents in poor conditions...

, parents in good conditions tend to invest more in sons (who are best able to take advantage of good conditions), while parents in poor conditions tend to invest more in daughters (who are best able to have successful offspring even in poor conditions). According to life history theory
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...

, animals evolve life histories to match their environments, determining details such as age at first reproduction and number of offspring. Dual inheritance theory
Dual inheritance theory
Dual inheritance theory , also known as gene-culture coevolution, was developed in the late 1970s and early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution...

 posits that genes and human culture have interacted, with genes affecting the development of culture and culture, in turn, affecting human evolution on a genetic level (see also the Baldwin effect
Baldwin effect
The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is a theory of a possible evolutionary processes that was originally put forward in 1896 in a paper, "A New Factor in Evolution," by American psychologist James Mark Baldwin. The paper proposed a mechanism for specific...

).

Evolved psychological mechanisms



Evolutionary psychology is based on the hypothesis that, just like hearts, lungs, livers, kidneys, and immune systems, cognition has functional structure that has a genetic basis, and therefore has evolved by natural selection. Like other organs and tissues, this functional structure should be universally shared amongst a species, and should solve important problems of survival and reproduction.

Evolutionary psychologists seek to understand psychological mechanisms
Psychological adaptation
A psychological adaptation, also called an Evolved psychological mechanism or EPM, is an aspect of a human or other animal's psychology that is the result of evolutionary pressures. It could serve a specific purpose, have served a purpose in the past , or be a side-effect of another EPM...

 by understanding the survival and reproductive functions they might have served over the course of evolutionary history. These might include abilities to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, cooperate with others. Consistent with the theory of natural selection, evolutionary psychology sees humans as often in conflict with others, including mates and relatives. Even mothers sometimes struggle with their children over weaning, which benefits the mother more than the child. Evolutionary psychology also recognizes the role of kin selection and reciprocity in evolving prosocial traits such as altruism. Like chimps and bonobos, humans have subtle and flexible social instincts, allowing them to form extended families, lifelong friendships, and political alliances. In studies testing theoretical predictions, evolutionary psychologists have made modest findings on topics such as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.

Products of evolution: adaptations, exaptations, byproducts, and random variation


Not all traits of organisms are adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s. As noted in the table below, traits may also be exaptation
Exaptation
Exaptation, cooption, and preadaptation are related terms referring to shifts in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another. Exaptations are common in both anatomy and behaviour...

s, byproducts of adaptations (sometimes called "spandrels"), or random variation between individuals.

Psychological adaptations are hypothesized to be innate or relatively easy to learn, and to manifest in cultures worldwide. For example, the ability of toddlers to learn a language with virtually no training is likely to be a psychological adaptation. On the other hand, ancestral humans did not read or write, thus today learning to read and write require extensive training, and presumably represent byproducts of cognitive processing that use psychological adaptations designed for other functions.
Adaptation Exaptation By-Product Random Noise
Definition Organismic trait designed to solve an ancestral problem(s). Shows complexity, special "design", functionality Adaptation that has been "re-designed" to solve a different adaptive problem. Byproduct of an adapative mechanism with no current or ancestral function Random variations in an adaptation or byproduct
Physiological Example Bones / Umbilical cord Small bones of the inner ear White color of bones / Belly button Bumps on the skull, convex or concave belly button shape
Psychological Example Toddlers’ ability to learn to talk with minimal instruction. Voluntary Attention Ability to learn to read and write. Within-sex variations in voice pitch.


One of the tasks of evolutionary psychology is to identify which psychological traits are likely to be adaptations, byproducts or random variation. George C Williams suggested that an "adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

 is a special and onerous concept that should only be used where it is really necessary". As noted by Williams and others, adaptations can be identified by their improbable complexity, species universality, and adaptive functionality.

Obligate and facultative adaptations


A question that may be asked about an adaptation is whether it is generally obligate (relatively robust in the face of typical environmental variation) or facultative (sensitive to typical environmental variation). The sweet taste of sugar and the pain of hitting one's knee against concrete are the result of fairly obligate psychological adaptations; typical environmental variability during development does not much affect their operation. By contrast, facultative adaptations are somewhat like "if-then" statements. For example, adult attachment style seems particularly sensitive to early childhood experiences. As adults, the propensity to develop close, trusting bonds with others is dependent on whether early childhood caregivers could be trusted to provide reliable assistance and attention. The adaptation for skin to tan is conditional to exposure to sunlight; this is an example of another facultative adaptation. When a psychological adaptation is facultative, evolutionary psychologists concern themselves with how developmental and environmental inputs influence the expression of the adaptation.

Cultural universals



Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations. Cultural universals include behaviors related to language, cognition, social roles, gender roles, and technology. Evolved psychological adaptations (such as the ability to learn a language) interact with cultural inputs to produce specific behaviors (e.g., the specific language learned). Basic gender differences, such as greater eagerness for sex among men and greater coyness among women, are explained as sexually dimorphic psychological adaptations that reflect the different reproductive strategies of males and females. Evolutionary psychologists contrast their approach to what they term the "standard social science model
Standard social science model
The term the Standard Social Science Model was first introduced to a wide audience by John Tooby and Leda Cosmides in the 1992 edited volume The Adapted Mind, to describe the "blank slate," social constructionist,or "cultural determinist" perspective that they claim is the dominant theoretical...

," according to which the mind is a general-purpose cognition device shaped almost entirely by culture.

Environment of evolutionary adaptedness



EP argues that to properly understand the functions of the brain, one must understand the properties of the environment in which the brain evolved. That environment is often referred to as the "environment of evolutionary adaptedness" (EEA).

The term "environment of evolutionary adaptedness" was coined by John Bowlby
John Bowlby
Edward John Mostyn "John" Bowlby was a British psychologist, psychiatrist and psychoanalyst, notable for his interest in child development and for his pioneering work in attachment theory.- Family background :...

 as part of attachment theory
Attachment theory
Attachment theory describes the dynamics of long-term relationships between humans. Its most important tenet is that an infant needs to develop a relationship with at least one primary caregiver for social and emotional development to occur normally. Attachment theory is an interdisciplinary study...

. It refers to the environment to which a particular evolved mechanism is adapted. More specifically, the EEA is defined as the set of historically recurring selection pressures that formed a given adaptation, as well as those aspects of the environment that were necessary for the proper development and functioning of the adaptation.

Humans, comprising the genus Homo
Homo (genus)
Homo is the genus that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis....

, appeared between 1.5 and 2.5 million years ago, a time that roughly coincides with the start of the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 1.8 million years ago. Because the Pleistocene ended a mere 12,000 years ago, most human adaptations either newly evolved during the Pleistocene, or were maintained by stabilizing selection
Stabilizing selection
-Description:Stabilizing or ambidirectional selection, , is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. This is probably the most common mechanism of action for natural selection...

 during the Pleistocene. Evolutionary psychology therefore proposes that the majority of human psychological mechanisms are adapted to reproductive problems frequently encountered in Pleistocene environments. In broad terms, these problems include those of growth, development, differentiation, maintenance, mating, parenting, and social relationships.

The EEA is significantly different from modern society. Our ancestors lived in smaller groups, had more cohesive cultures, and had more stable and rich contexts for identity and meaning. Researchers look to existing hunter-gatherer societies for clues as to how our hunter-gatherer ancestors lived. Since hunter-gatherer societies are egalitarian, the ancestral population may have been egalitarian as well, a social pattern different from the hierarchies found in chimp bands. Unfortunately, the few surviving hunter-gatherer societies are different from each other, and they have been pushed out of the best land and into harsh environments, so it is not clear how closely they reflect ancestral culture.

Evolutionary psychologists sometimes look to chimpanzees, bonobos, and other great apes for insight into human ancestral behavior. Christopher Ryan and Cacilda Jetha argue that evolutionary psychologists have overemphasized our similarity to chimps, which are more violent, while underestimating our similarity to bonobos, which are more peaceful.

Mismatches


Since an organism's adaptations were suited to its ancestral environment, a new and different environment can create a mismatch. Because humans are mostly adapted to Pleistocene environments, psychological mechanisms sometimes exhibit "mismatches" to the modern environment. One example is the fact that although about 10,000 people are killed with guns in the US annually, whereas spiders and snakes kill only a handful, people nonetheless learn to fear spiders and snakes about as easily as they do a pointed gun, and more easily than an unpointed gun, rabbits or flowers. A potential explanation is that spiders and snakes were a threat to human ancestors throughout the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

, whereas guns (and rabbits and flowers) were not. There is thus a mismatch between our evolved fear-learning psychology and the modern environment.

This mismatch also shows up in the phenomena of the supernormal stimulus, a stimulus that elicits a response more strongly than the stimulus for which the response evolved. The term was coined by Niko Tinbergen to describe animal behavior, but psychologist Deirdre Barrett
Deirdre Barrett
Deirdre Barrett, Ph.D. is an author and psychologist who teaches at Harvard Medical School. She is known for her research on dreams, hypnosis, and imagery and has written on evolutionary psychology. Barrett is a Past President of The International Association for the Study of Dreams and of the...

 said that supernormal stimulation governs the behavior of humans as powerfully as that of animals. She explained junk food as an exaggerated stimulus to cravings for salt, sugar, and fats, and she says that television is an exaggeration of social cues of laughter, smiling faces and attention-grabbing action. Magazine centerfolds and double cheeseburgers pull instincts intended for an EEA where breast development was a sign of health, youth and fertility in a prospective mate, and fat was a rare and vital nutrient.

Research methods


Evolutionary theory is heuristic
Heuristic
Heuristic refers to experience-based techniques for problem solving, learning, and discovery. Heuristic methods are used to speed up the process of finding a satisfactory solution, where an exhaustive search is impractical...

 in that it may generate hypotheses that might not be developed from other theoretical approaches. One of the major goals of adaptationist research is to identify which organismic traits are likely to be adaptations, and which are byproducts or random variations. As noted earlier, adaptations are expected to show evidence of complexity, functionality, and species universality, while byproducts or random variation will not. In addition, adaptations are expected to manifest as proximate mechanisms that interact with the environment in either a generally obligate or facultative fashion (see above). Evolutionary psychologists are also interested in identifying these proximate mechanisms (sometimes termed "mental mechanisms" or "psychological adaptations") and what type of information they take as input, how they process that information, and their outputs. Evolutionary developmental psychology
Evolutionary developmental psychology
Evolutionary developmental psychology, , is the application of the basic principles of Darwinian evolution, particularly natural selection, to explain contemporary human development...

, or "evo-devo," focuses on how adaptations may be activated at certain developmental times (e.g., losing baby teeth, adolescence, etc.) or how events during the development of an individual may alter life history
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...

 trajectories.

Evolutionary psychologists use several strategies to develop and test hypotheses about whether a psychological trait is likely to be an evolved adaptation. Buss (2011) notes that these methods include:
Cross-cultural Consistency. Characteristics that that been demonstrated to be cross cultural human universals
Human Universals
Human Universals is a book by Donald Brown, an American professor of anthropology who worked at the University of California, Santa Barbara. It was published by McGraw Hill in 1991...

 such as smiling, crying, facial expressions are presumed to be evolved psychological adaptations. Several evolutionary psychologists have collected massive datasets from cultures around the world to assess cross-cultural universalty.

Function to Form (or "problem to solution"). The fact that males, but not females, risk potential misidentification of genetic offspring (referred to as "paternity insecurity") led evolutionary psychologists to hypothesize that, compared to females, male jealousy would be more focused on sexual, rather than emotional, infidelity.

Form to Function (reverse-engineering -- or "solution to problem"). Morning sickness
Morning sickness
Morning sickness, also called nausea gravidarum, nausea, vomiting of pregnancy , or pregnancy sickness is a condition that affects more than half of all pregnant women. Related to increased oestrogen levels, a similar form of nausea is also seen in some women who use hormonal contraception or...

, and associated aversions to certain types of food, during pregnancy seemed to have the characteristics of an evolved adaptation (complexity and universality). Margie Profet
Margie Profet
Margie Profet is an American evolutionary biologist with no formal biology training who created a decade-long controversy when she published her findings on the role of Darwinian evolution in menstruation, allergies and morning sickness....

 hypothesized that the function was to avoid the ingestion of toxins during early pregnancy that could damage fetus (but which are likely harmless to healthy women).

Corresponding Neurological Modules Evolutionary psychology and cognitive neuropsychology are mutually compatible -- evolutionary psychology helps to identify psychological adaptations and their ultimate, evolutionary functions, while neuropsychology helps to identify the proximate manifestations of these adaptations.


Evolutionary psychologists also use various sources of data for testing, including experiments, archeological records, data from hunter-gatherer societies, observational studies, self-reports and surveys, public records, and human products.
Recently, additional methods and tools have been introduced based on fictional scenarios, mathematical models, and multi-agent computer simulations.

Major areas of research


Foundational areas of research in evolutionary psychology can be divided into broad categories of adaptive problems that arise from the theory of evolution itself: survival, mating, parenting, family and kinship, interactions with non-kin, and cultural evolution.

Survival and individual level psychological adaptations


Problems of survival are thus clear targets for the evolution of physical and psychological adaptations. Major problems our ancestors faced included food selection and acquisition; territory selection and physical shelter; and avoiding predators and other environmental threats.

Consciousness



Consciousness is likely an evolved adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

 since it meets George Williams
George C. Williams
Professor George Christopher Williams was an American evolutionary biologist.Williams was a professor emeritus of biology at the State University of New York at Stony Brook. He was best known for his vigorous critique of group selection. The work of Williams in this area, along with W. D...

' criteria of species universality, complexity, and functionality, and it is a trait that apparently increases fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

.

In his paper "Evolution of consciousness," John Eccles argues that special anatomical and physical adaptations of the mammalian cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

 gave rise to consciousness. In contrast, others have argued that the recursive circuitry underwriting consciousness is much more primitive, having evolved initially in pre-mammalian species because it improves the capacity for interaction with both social and natural environments by providing an energy-saving "neutral" gear in an otherwise energy-expensive motor output machine. Once in place, this recursive circuitry may well have provided a basis for the subsequent development of many of the functions that consciousness facilitates in higher organisms, as outlined by Bernard J. Baars. Richard Dawkins suggested that we evolved consciousness in order to make ourselves the subjects of thought. Daniel Povinelli suggests that large, tree-climbing apes evolved consciousness to take into account one's own mass when moving safely among tree branches. Consistent with this hypothesis, Gordon Gallup found that chimps and orangutans, but not little monkeys or terrestrial gorillas, demonstrated self-awareness in mirror tests.

The concept of consciousness can refer to voluntary action, awareness, or wakefulness. However, even voluntary behavior involves unconscious mechanisms.Many cognitive processes take place in the cognitive unconscious, unavailable to conscious awareness. Some behaviors are conscious when learned but then become unconscious, seemingly automatic. Learning, especially implicitly learning a skill, can take place outside of consciousness. For example, plenty of people know how to turn right when they ride a bike, but very few can accurately explain how they actually do so.

Sleep may have evolved to conserve energy when activity would be less fruitful or more dangerous, such as at night, especially in winter.

Sensation and perception


Many experts, such as Jerry Fodor
Jerry Fodor
Jerry Alan Fodor is an American philosopher and cognitive scientist. He holds the position of State of New Jersey Professor of Philosophy at Rutgers University and is the author of many works in the fields of philosophy of mind and cognitive science, in which he has laid the groundwork for the...

, write that the purpose of perception is knowledge, but evolutionary psychologists hold that its primary purpose is to guide action. For example, they say, depth perception
Depth perception
Depth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth sensation is the ability to move accurately, or to respond consistently, based on the distances of objects in an environment....

 seems to have evolved not to help us know the distances to other objects but rather to help us move around in space. Evolutionary psychologists say that animals from fiddler crabs to humans use eyesight for collision avoidance, suggesting that vision is basically for directing action, not providing knowledge.

Building and maintaining sense organs is metabolically expensive, so these organs evolve only when they improve an organism's fitness. More than half the brain is devoted to processing sensory information, and the brain itself consumes roughly one-fourth of one's metabolic resources, so the senses must provide exceptional benefits to fitness. Perception accurately mirrors the world; animals get useful, accurate information through their senses.

Scientists who study perception and sensation have long understood the human senses as adaptations. Depth perception consists of processing over half a dozen visual cues, each of which is based on a regularity of the physical world. Vision evolved to respond to the narrow range of electromagnetic energy that is plentiful and that does not pass through objects. Sound waves go around corners and interact with obstacles, creating a complex pattern that includes useful information about the sources of and distances to objects. Larger animals naturally make lower-pitched sounds as a consequence of their size. The range over which an animal hears, on the other hand, is determined by adaptation. Homing pigeons, for example, can hear very low-pitched sound (infrasound) that carries great distances, even though most smaller animals detect higher-pitched sounds. Taste and smell respond to chemicals in the environment that are thought to have been significant for fitness in the EEA. For example, salt and sugar were apparently both valuable to our ancestors, and we favor salty and sweet tastes. The sense of touch is actually many senses, including pressure, heat, cold, tickle, and pain. Pain, while unpleasant, is adaptive. An important adaptation for senses is range shifting, by which the organism becomes temporarily more or less sensitive to sensation. For example, one's eyes automatically adjust to dim or bright ambient light. Sensory abilities of different organisms often coevolve, as is the case with the hearing of echolocating bats and that of the moths that have evolved to respond to the sounds that the bats make.

Evolutionary psychologists claim that perception demonstrates the principle of modularity, with specialized mechanisms handling particular perception tasks. For example, people with damage to a particular part of the brain suffer from the specific defect of not being able to recognize faces (prospagnosia). EP suggests that this indicates a so-called face-reading module.

Learning and facultative adaptations


In evolutionary psychology, learning is said to be accomplished through evolved capacities, specifically facultative adaptations. Facultative adaptations express themselves differently depending on input from the environment. Sometimes the input comes during development and helps shape that development. For example, migrating birds learn to orient themselves by the stars during a critical period in their maturation. Evolutionary psychologists claim that humans also learn language along an evolved program, also with critical periods. The input can also come during daily tasks, helping the organism cope with changing environmental conditions. For example, animals evolved Pavlovian conditioning in order to solve problems about causal relationships. Animals accomplish learning tasks most easily when those tasks resemble problems that they faced in their evolutionary past, such as a rat learning where to find food or water. Learning capacities sometimes demonstrate differences between the sexes. In many animal species, for example, males can solve spatial problem faster and more accurately than females, due to the effects of male hormones during development. The same might be true of humans.

Emotion and motivation


Motivations direct and energize behavior, while emotions provide the affective component to motivation, positive or negative. In the early 1970s, Paul Ekman
Paul Ekman
Paul Ekman is a psychologist who has been a pioneer in the study of emotions and their relation to facial expressions. He has been considered one of the 100 most eminent psychologists of the twentieth century...

 and colleagues began a line of research that suggests that many emotions are universal. He found evidence that humans share at least five basic emotions: fear, sadness, happiness, anger, and disgust. Social emotions evidently evolved to motivate social behaviors that were adaptive in the EEA. For example, spite seems to work against the individual but it can establish an individual's reputation as someone to be feared. Shame and pride can motivate behaviors that help one maintain one's standing in a community, and self-esteem is one's estimate of one's status.

Cognition


Cognition refers to internal representations of the world and internal information processing. From an EP perspective, cognition is not "general purpose," but uses heuristics, or strategies, that generally increase the likelihood of solving problems our ancestors routinely faced. For example, humans are far more likely to solve logic problems that involve detecting cheating (a common problem given our social nature) than the same logic problem put in purely abstract terms. Since our ancestors did not encounter truly random events, we may be cognitively predisposed to incorrectly identify patterns in random sequences. "Gamblers' Fallacy" is one example of this. Gamblers may falsely believe that they have hit a "lucky streak" even when each outcome is actually random and independent of previous trials. Most people believe that if a fair coin has been flipped 9 times and Heads appears each time, that on the tenth flip, there is a greater than 50% chance of getting Tails. Humans find it far easier to make diagnoses or predictions using frequency data than when the same information is presented as probabilities or percentages, presumably because our ancestors lived in relatively small tribes (usually with fewer that 150 people) where frequency information was more readily available.

Personality


Evolutionary psychology is primarily interested in finding commonalities between people, or basic human psychological nature. From an evolutionary perspective, the fact that people have fundamental differences in personality traits initially presents something of a puzzle. (Note: The field of behavioral genetics
Behavioural genetics
Quantitative human behavioural genetics is a specialisation in the biological field of behaviour genetics that studies the role of genetics in human behaviour employing quantitative-genetic methods. The field is an overlap of quantitative genetics and psychology...

 is concerned with statistically partitioning differences between people into genetic and environmental sources of variance. However, understanding the concept of heritability
Heritability
The Heritability of a population is the proportion of observable differences between individuals that is due to genetic differences. Factors including genetics, environment and random chance can all contribute to the variation between individuals in their observable characteristics...

 can be tricky—heritability refers only to the differences between people, never the degree to which the traits of an individual are due to environmental or genetic factors, since traits are always a complex interweaving of both.)

Personality traits are conceptualized by evolutionary psychologists as due to normal variation around an optimum, or due to frequency-dependent selection, or facultative adaptations. Like variability in height, some personality traits may be simply reflect inter-individual variability around a general optimum. Or, personality traits may represent different genetically predisposed "behavioral morphs" -- alternate behavioral strategies that depend on the frequency of competing behavioral strategies in the population. For example, if most of the population is generally trusting and gullible, the behavioral morph of being a "cheater" (or, in the extreme case, a sociopath) may be advantageous. Finally, like many other psychological adaptations, personality traits may be facultative—sensitive to typical variations in the social environment, especially during early development. For example, later born children are more likely than first borns to be rebellious, less conscientious and more open to new experiences, which may be advantageous to them given their particular niche in family structure.

Language



According to Steven Pinker
Steven Pinker
Steven Arthur Pinker is a Canadian-American experimental psychologist, cognitive scientist, linguist and popular science author...

, who builds on the work by Noam Chomsky
Noam Chomsky
Avram Noam Chomsky is an American linguist, philosopher, cognitive scientist, and activist. He is an Institute Professor and Professor in the Department of Linguistics & Philosophy at MIT, where he has worked for over 50 years. Chomsky has been described as the "father of modern linguistics" and...

, the universal human ability to learn to talk between the ages of 1 - 4, basically without training, suggests that language acquisition is a distinctly human psychological adaptation (see, in particular, Pinker's The Language Instinct
The Language Instinct
The Language Instinct is a book by Steven Pinker for a general audience, published in 1994. In it, Pinker argues that humans are born with an innate capacity for language. In addition, he deals sympathetically with Noam Chomsky's claim that all human language shows evidence of a universal grammar...

). Pinker and Bloom (1990) argue that language as a mental faculty shares many likenesses with the complex organs of the body which suggests that, like these organs, language has evolved as an adaptation, since this is the only known mechanism by which such complex organs can develop. Pinker follows Chomsky in arguing that the fact that children can learn any human language with no explicit instruction suggests that language, including most of grammar, is basically innate and that it only needs to be activated by interaction. Chomsky himself does not believe language to have evolved as an adaption, but suggests that it likely evolved as a byproduct of some other adaptation, a so-called spandrel
Spandrel
A spandrel, less often spandril or splaundrel, is the space between two arches or between an arch and a rectangular enclosure....

. But Pinker and Bloom argue that the organic nature of language strongly suggests that it has an adaptational origin.

Evolutionary psychologists hold that the FOXP2
FOXP2
Forkhead box protein P2 also known as FOXP2 is a protein that in humans is encoded by the FOXP2 gene, located on human chromosome 7 . FOXP2 orthologs have also been identified in all mammals for which complete genome data are available...

 gene may well be associated with the evolution of human language. In the 1980s, psycholinguist Myrna Gropnik identified a dominant gene that causes language impairment in the KE family of Britain. This gene turned out to be a mutation of the FOXP2 gene. Humans have a unique allele of this gene, which has otherwise been closely conserved through most of mammalian evolutionary history. This unique allele seems to have first appeared between 100 and 200 thousand years ago, and it is now all but universal in humans.

Currently several competing theories about the evolutionary origin of language coexist, none of them having achieved a general consensus. Researchers of language acquisition in primates and humans such as Michael Tomasello
Michael Tomasello
Michael Tomasello is an American developmentalpsychologist. He is a co-director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.-Life:...

 and Talmy Givón
Talmy Givón
Thomas Givon is a linguist and writer. He is one of the founders of functionalism in linguistics...

, argue that the innatist framework has understated the role of imitation in learning and that it is not at all necessary to posit the existence of an innate grammar module to explain human language acquisition. Tomasello argues that studies of how children and primates actually acquire communicative skills suggests that we learn complex behavior through experience, so that instead of a module specifically dedicated to language acquisition, language is acquired by the same cognitive mechanisms that are used to acquire all other kinds of socially transmitted behavior.

On the issue of whether language is best seen as having evolved as an adaptation or as a spandrel, evolutionary biologist W. Tecumseh Fitch
W. Tecumseh Fitch
William Tecumseh Sherman Fitch III is an American evolutionary biologist and cognitive scientist, and at the University of Vienna , where he is co-founder of the...

, following Stephen J. Gould, argues that it is unwarranted to assume that every aspect of language is an adaptation, or that language as a whole is an adaptation. He criticizes some strands of evolutionary psychology for suggesting a pan-adaptionist view of evolution, and dismisses Pinker and Bloom's question of whether "Language has evolved as an adaptation" as being misleading. He argues instead that from a biological viewpoint the evolutionary origins of language is best conceptualized as being the probable result of a convergence of many separate adaptions into a complex system. A similar argument is made by Terrence Deacon
Terrence Deacon
Terrence William Deacon is an American anthropologist . He taught at Harvard for eight years, relocated to Boston University in 1992, and is currently Professor of Biological Anthropology and Neuroscience at the University of California, Berkeley.-Theoretical interests:Prof...

 who in The Symbolic Species argues that the different features of language have co-evolved with the evolution of the mind and that the ability to use symbolic communication is integrated in all other cognitive processes.

If the theory that language could have evolved as a single adaptation is accepted, the question becomes which of its many functions has been the basis of adaptation, several evolutionary hypotheses have been posited: that it evolved for the person of social grooming, that it evolved to as way to show mating potential or that it evolved to form social contracts. Evolutionary psychologists recognize that these theories are all speculative and that much more evidence is required to understand how language might have been selectively adapted.

Mating


Given that sexual reproduction is the means by which genes are propagated into future generations, sexual selection plays a large role in the direction of human evolution. Human mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...

, then, is of interest to evolutionary psychologists who aim to investigate evolved mechanisms to attract and secure mates. Several lines of research have stemmed from this interest, such as studies of mate selection mate poaching, and mate retention.

Much of the research on human mating is based on parental investment
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

 theory, which makes important predictions about the different strategies men and women will use in the mating domain (see above under "Middle-level evolutionary theories"). In essence, it predicts that women will be more selective when choosing mates, whereas men will not, especially under short-term mating conditions. This has led some researchers to predict sex differences in such domains as sexual jealousy
Sexual jealousy
Sexual jealousy is a special form of jealousy in sexual relationships, present in animals that reproduce through internal fertilization, and is based on suspected or imminent sexual infidelity. It is founded on the instinct of keeping genes in the gene pool and expecting sexual partners to care for...

, (however, see also,) wherein females will react more aversively to emotional infidelity and males will react more aversively to sexual infidelity. This particular pattern is predicted because the costs involved in mating for each sex are distinct. Women, on average, should prefer a mate who can offer some kind of resources (e.g., financial, commitment), which means that a woman would also be more at risk for losing those valued traits in a mate who commits an emotional infidelity. Men, on the other hand, are limited by the fact that they can never be certain of the paternity of their children because they do not bear the offspring themselves. This obstacle entails that sexual infidelity would be more aversive than emotional infidelity for a man because investing resources in another man's offspring does not lead to propagation of the man's own genes.

Another interesting line of research is that which examines women's mate preferences across the ovulatory cycle
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...

. The theoretical underpinning of this research is that ancestral women would have evolved mechanisms to select mates with certain traits depending on their hormonal status. For example, the theory hypothesizes that, during the ovulatory phase of a woman's cycle (approximately days 10-15 of a woman's cycle), a woman who mated with a male with high genetic quality would have been more likely, on average, to produce and rear a healthy offspring than a woman who mated with a male with low genetic quality. These putative preferences are predicted to be especially apparent for short-term mating domains because a potential male mate would only be offering genes to a potential offspring. This hypothesis allows researchers to examine whether women select mates who have characteristics that indicate high genetic quality during the high fertility phase of their ovulatory cycles. Indeed, studies have shown that women's preferences vary across the ovulatory cycle. In particular, Haselton and Miller (2006) showed that highly fertile women prefer creative but poor men as short-term mates. Creativity may be a proxy for good genes. Research by Gangestad et al. (2004) indicates that highly fertile women prefer men who display social presence and intrasexual competition; these traits may act as cues that would help women predict which men may have, or would be able to acquire, resources.

Parenting


Reproduction is always costly for women, and can also be for men. Individuals are limited in the degree to which they can devote time and resources to producing and raising their young, and such expenditure may also be detrimental to their future condition, survival and further reproductive output.
Parental investment
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

 is any parental expenditure (time, energy etc.) that benefits one offspring
Offspring
In biology, offspring is the product of reproduction, of a new organism produced by one or more parents.Collective offspring may be known as a brood or progeny in a more general way...

 at a cost to parent
Parent
A parent is a caretaker of the offspring in their own species. In humans, a parent is of a child . Children can have one or more parents, but they must have two biological parents. Biological parents consist of the male who sired the child and the female who gave birth to the child...

s' ability to invest in other components of fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

 (Clutton-Brock 1991: 9; Trivers 1972). Components of fitness (Beatty 1992) include the well being of existing offspring, parents' future reproduction
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...

, and inclusive fitness
Inclusive fitness
In evolutionary biology and evolutionary psychology, the inclusive fitness of an organism is the sum of its classical fitness and the number of equivalents of its own offspring it can add to the population by supporting others...

 through aid to kin (Hamilton
W. D. Hamilton
William Donald Hamilton FRS was a British evolutionary biologist, widely recognised as one of the greatest evolutionary theorists of the 20th century....

, 1964). Parental investment theory is a branch of life history theory
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...

.

Robert Trivers
Robert Trivers
Robert L. Trivers is an American evolutionary biologist and sociobiologist and Professor of Anthropology and Biological Sciences at Rutgers University. Trivers is most noted for proposing the theories of reciprocal altruism , parental investment , facultative sex ratio determination , and...

' theory of parental investment predicts that the sex
Sex
In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

 making the largest investment in lactation
Lactation
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...

, nurturing and protecting offspring will be more discriminating in mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...

 and that the sex that invests less in offspring will compete for access to the higher investing sex (see Bateman's principle
Bateman's principle
In biology, Bateman's principle is the theory that females almost always invest more energy into producing offspring than males invest, and therefore in most species females are a limiting resource over which the other sex will compete...

). Sex differences in parental effort are important in determining the strength of sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

.

The benefits of parental investment to the offspring are large and are associated with the effects on condition, growth, survival and ultimately, on reproductive success of the offspring. However, these benefits can come at the cost of parent's ability to reproduce in the future e.g. through the increased risk of injury when defending offspring against predators, the loss of mating opportunities whilst rearing offspring and an increase in the time to the next reproduction. Overall, parents are selected
Selection
In the context of evolution, certain traits or alleles of genes segregating within a population may be subject to selection. Under selection, individuals with advantageous or "adaptive" traits tend to be more successful than their peers reproductively—meaning they contribute more offspring to the...

 to maximise the difference between the benefits and the costs, and parental care will be likely to evolve when the benefits exceed the costs.

The Cinderella effect
Cinderella Effect
The Cinderella effect is a term used by psychologists to describe the high incidence of stepchildren being physically abused, emotionally abused, sexually abused, neglected, murdered, or otherwise mistreated at the hands of their stepparents at significantly higher rates than at the hands of their...

 is a term used to describe the high incidence of stepchildren being physically, emotionally or sexually abused, neglected or murdered, or otherwise mistreated at the hands of their stepparents at significantly higher rates than their genetic counterparts. It takes its name from the fairy tale character Cinderella, who in the story was cruelly mistreated by her stepmother and stepsisters. Daly and Wilson (1996) noted: "Evolutionary thinking led to the discovery of the most important risk factor for child homicide -- the presence of a stepparents. Parental efforts and investments are valuable resources, and selection favors those parental psyches that allocate effort effectively to promote fitness. The adaptive problems that challenge parental decision making include both the accurate identification of one's offspring and the allocation of one's resources among them with sensitivity to their needs and abilities to convert parental investment into fitness increments…. Stepchildren were seldom or never so valuable to one's expected fitness as one's own offspring would be, and those parental psyches that were easily parasitized by just any appealing youngster must always have incurred a selective disadvantage"(Daly & Wilson, 1996, p64 - 65). However, they note that not all stepparents will "want" to abuse their partner's children, or that genetic parenthood is absolute insurance against abuse. They see step parental care is as primarily "mating effort" towards the genetic parent.

Family and kin


Inclusive fitness
Inclusive fitness
In evolutionary biology and evolutionary psychology, the inclusive fitness of an organism is the sum of its classical fitness and the number of equivalents of its own offspring it can add to the population by supporting others...

 is the sum of an organism's classical fitness (how many of its own offspring it produces and supports) and the number of equivalents of its own offspring it can add to the population by supporting others. The first component is called classical fitness by Hamilton (1964).

From the gene's point of view, evolutionary success ultimately depends on leaving behind the maximum number of copies of itself in the population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

. Until 1964, it was generally believed that genes only achieved this by causing the individual to leave the maximum number of viable offspring. However, in 1964 W. D. Hamilton proved mathematically that, because close relatives of an organism share some identical genes, a gene can also increase its evolutionary success by promoting the reproduction and survival of these related or otherwise similar individuals. Hamilton claimed that this leads natural selection to favor organisms that would behave in ways that maximize their inclusive fitness. It is also true that natural selection favors behavior that maximizes personal fitness.

Hamilton's rule describes mathematically whether or not a gene for altruistic behaviour will spread in a population:
where
  • is the reproductive cost to the altruist,
  • is the reproductive benefit to the recipient of the altruistic behavior, and
  • is the probability, above the population average, of the individuals sharing an altruistic gene – commonly viewed as "degree of relatedness".


The concept serves to explain how natural selection can perpetuate altruism
Altruism
Altruism is a concern for the welfare of others. It is a traditional virtue in many cultures, and a core aspect of various religious traditions, though the concept of 'others' toward whom concern should be directed can vary among cultures and religions. Altruism is the opposite of...

. If there is an '"altruism gene"' (or complex of genes) that influences an organism's behavior to be helpful and protective of relatives and their offspring, this behavior also increases the proportion of the altruism gene in the population, because relatives are likely to share genes with the altruist due to common descent. Altruists may also have some way to recognize altruistic behavior in unrelated individuals and be inclined to support them. As Dawkins points out in The Selfish Gene (Chapter 6) and The Extended Phenotype, this must be distinguished from the green-beard effect
Green-beard effect
The gene-centered view of evolution postulates that natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication...

.

Psychological adaptations related to interactions with kin are facultative. Although it is generally true that humans tend to be more altruistic toward their kin than toward non-kin, there may be exceptions. Specific types of behavioral output are dependent on the interaction of both genetic and environmental influences. For example, John Bowlby and others have noted that patterns of attachment to others are dependent on early developmental experiences with caregivers. In any specific instance, the manifestation of emotional bonds into altruistic behaviour depends on early bonding experiences, and symbolic, economic and other cultural factors, which may or may not always coincide with consanguinity.

Interactions with non-kin / reciprocity


Although interactions with non-kin are generally less altruistic compared to those with kin, cooperation can be maintained with non-kin via mutually beneficial reciprocity
Reciprocity (evolution)
Reciprocity in evolutionary biology refers to mechanisms whereby the evolution of cooperative or altruistic behaviour may be favoured by the probability of future mutual interactions...

 as was proposed by Robert Trivers
Robert Trivers
Robert L. Trivers is an American evolutionary biologist and sociobiologist and Professor of Anthropology and Biological Sciences at Rutgers University. Trivers is most noted for proposing the theories of reciprocal altruism , parental investment , facultative sex ratio determination , and...

. If there are repeated encounters between the same two players in an evolutionary game in which each of them can choose either to "cooperate" or "defect," then a strategy of mutual cooperation may be favored even if it pays each player, in the short term, to defect when the other cooperates. Direct reciprocity can lead to the evolution of cooperation only if the probability, w, of another encounter between the same two individuals exceeds the cost-to-benefit ratio of the altruistic act:
w > c/b


Reciprocity can also be indirect if information about previous interactions is shared. Reputation allows evolution of cooperation by indirect reciprocity. Natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 favors strategies that base the decision to help on the reputation of the recipient: studies show that people who are more helpful are more likely to receive help. The calculations of indirect reciprocity are complicated and only a tiny fraction of this universe has been uncovered, but again a simple rule has emerged. Indirect reciprocity can only promote cooperation if the probability, q, of knowing someone’s reputation exceeds the cost-to-benefit ratio of the altruistic act:
q > c/b


One important problem with this explanation is that individuals may be able to evolve the capacity to obscure their reputation, reducing the probability, q, that it will be known.

Trivers argues that friendship and various social emotions evolved in order to manage reciprocity. Liking and disliking, he says, evolved to help our ancestors form coalitions with others who reciprocated and to exclude those who did not reciprocate. Moral indignation may have evolved to prevent one's altruism from being exploited by cheaters, and gratitude may have motivated our ancestors to reciprocate appropriately after benefiting from others' altruism. Likewise, we feel guilty when we fail to reciprocate. These social motivations match what evolutionary psychologists expect to see in adaptations that evolved to maximize the benefits and minimize the drawbacks of reciprocity.

Evolutionary psychologists say that humans have psychological adaptations that evolved specifically to help us identify nonreciprocators, commonly referred to as "cheaters." In 1993, Robert Frank and his associates found that participants in a prisoner's dilemma scenario were often able to predict whether their partners would "cheat," based on a half hour of unstructured social interaction. In a 1996 experiment, for example, Linda Mealey and her colleagues found that people were better at remembering the faces of people when those faces were associated with stories about those individuals cheating (such as embezzling money from a church).

Evolution and culture


Evolutionary psychology incorporates insights derived from other disciplines about how cultural phenomena evolve over time. Theories that have applied evolutionary perspectives to cultural phenomena include memetics
Memetics
Memetics is a theory of mental content based on an analogy with Darwinian evolution, originating from Richard Dawkins' 1976 book The Selfish Gene. It purports to be an approach to evolutionary models of cultural information transfer. A meme, analogous to a gene, is essentially a "unit of...

, cultural ecology
Cultural ecology
Cultural ecology studies the relationship between a given society and its natural environment as well as the life-forms and ecosystems that support its lifeways . This may be carried out diachronically , or synchronically...

, and dual inheritance theory
Dual inheritance theory
Dual inheritance theory , also known as gene-culture coevolution, was developed in the late 1970s and early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution...

 (gene-culture co-evolution).

Memetics is a theory of mental content based on an analogy with evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

, originating from Richard Dawkins
Richard Dawkins
Clinton Richard Dawkins, FRS, FRSL , known as Richard Dawkins, is a British ethologist, evolutionary biologist and author...

' 1976 book The Selfish Gene
The Selfish Gene
The Selfish Gene is a book on evolution by Richard Dawkins, published in 1976. It builds upon the principal theory of George C. Williams's first book Adaptation and Natural Selection. Dawkins coined the term "selfish gene" as a way of expressing the gene-centred view of evolution as opposed to the...

.
It purports to be an approach to evolutionary models of cultural information transfer
Information transfer
In telecommunications, information transfer is the process of moving messages containing user information from a source to a sink.Note: The information transfer rate may or may not be equal to the transmission modulation rate.-See also:...

. A meme
Meme
A meme is "an idea, behaviour or style that spreads from person to person within a culture."A meme acts as a unit for carrying cultural ideas, symbols or practices, which can be transmitted from one mind to another through writing, speech, gestures, rituals or other imitable phenomena...

, analogous to a gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

, is essentially a "unit of culture"—an idea, belief, pattern of behavior, etc. which is "hosted" in one or more individual minds, and which can reproduce itself from mind to mind. Thus what would otherwise be regarded as one individual influencing another to adopt a belief is seen memetically as a meme reproducing itself. As with genetics, particularly under Dawkins's interpretation, a meme's success may be due to its contribution to the effectiveness of its host. Memetics is notable for sidestepping the traditional concern with the truth
Truth
Truth has a variety of meanings, such as the state of being in accord with fact or reality. It can also mean having fidelity to an original or to a standard or ideal. In a common usage, it also means constancy or sincerity in action or character...

of ideas and beliefs.

Susan Blackmore
Susan Blackmore
Susan Jane Blackmore is an English freelance writer, lecturer, and broadcaster on psychology and the paranormal, perhaps best known for her book The Meme Machine.-Career:...

 (2002) re-stated the definition of meme as: whatever is copied from one person to another person, whether habits, skills, songs, stories, or any other kind of information. Further she said that memes, like genes, are replicators in the sense as defined by Dawkins. That is, they are information that is copied. Memes are copied by imitation
Imitation
Imitation is an advanced behavior whereby an individual observes and replicates another's. The word can be applied in many contexts, ranging from animal training to international politics.-Anthropology and social sciences:...

, teaching and other methods. The copies are not perfect: memes are copied with variation; moreover, they compete for space in our memories and for the chance to be copied again. Only some of the variants can survive. The combination of these three elements (copies; variation; competition for survival) forms precisely the condition for Darwinian evolution, and so memes (and hence human cultures) evolve. Large groups of memes that are copied and passed on together are called co-adapted meme complexes, or memeplexes. In her definition, the way that a meme replicates is through imitation.

Dual inheritance theory
Dual inheritance theory
Dual inheritance theory , also known as gene-culture coevolution, was developed in the late 1970s and early 1980s to explain how human behavior is a product of two different and interacting evolutionary processes: genetic evolution and cultural evolution...

 (DIT), also known as gene-culture coevolution, suggests that cultural information and genes co-evolve. Marcus Feldman and Luigi Luca Cavalli-Sforza
Luigi Luca Cavalli-Sforza
Luigi Luca Cavalli-Sforza is an Italian population geneticist born in Genoa, who has been a professor at Stanford University since 1970 .-Books:...

 (1976) published perhaps the first dynamic models of gene-culture coevolution. These models were to form the basis for subsequent work on DIT, heralded by the publication of three seminal books in 1980 and 1981. Charles Lumsden and E.O. Wilson's
E. O. Wilson
Edward Osborne Wilson is an American biologist, researcher , theorist , naturalist and author. His biological specialty is myrmecology, the study of ants....

 Genes, Mind and Culture (1981). also outlined a series of mathematical models of how genetic evolution might favor the selection of cultural traits and how cultural traits might, in turn, affect the speed of genetic evolution. Another 1981 book relevant to this topic was Cavalli-Sforza
Luigi Luca Cavalli-Sforza
Luigi Luca Cavalli-Sforza is an Italian population geneticist born in Genoa, who has been a professor at Stanford University since 1970 .-Books:...

 and Feldman's Cultural Transmission and Evolution: A Quantitative Approach. Borrowing heavily from population genetics
Population genetics
Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population...

 and epidemiology
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

, this book built a mathematical theory concerning the spread of cultural traits. It describes the evolutionary implications of vertical transmission
Vertical transmission
Vertical transmission, also known as mother-to-child transmission, is the transmission of an infection or other disease from mother to child immediately before and after birth during the perinatal period. A pathogen's transmissibility refers to its capacity for vertical transmission...

, passing cultural traits from parents to offspring; oblique transmission, passing cultural traits from any member of an older generation to a younger generation; and horizontal transmission
Horizontal transmission
Horizontal transmission is the transmission of a bacterial, fungal, or viral infection between members of the same species that are not in a parent-child relationship....

, passing traits between members of the same population.

Robert Boyd and Peter Richerson's (1985) Culture and the Evolutionary Process presents models of the evolution of social learning under different environmental conditions, the population effects of social learning, various forces of selection on cultural learning rules, different forms of biased transmission and their population-level effects, and conflicts between cultural and genetic evolution.

Along with game theory
Game theory
Game theory is a mathematical method for analyzing calculated circumstances, such as in games, where a person’s success is based upon the choices of others...

, Herbert Gintis
Herbert Gintis
Herbert Gintis is an American behavioral scientist, educator, and author. He is notable for his foundational views on Altruism, Cooperation, Epistemic Game Theory, Gene-culture coevolution, Efficiency wages, Strong reciprocity, and Human capital theory. Gintis has also written extensively on...

 suggested that Dual Inheritance Theory has potential for unifying the behavioral sciences, including economics, biology, anthropology, sociology, psychology and political science because it addresses both the genetic and cultural components of human inheritance. Laland and Brown hold a similar view.

Developmental psychology


In evolutionary theory, what matters most is that individuals live long enough to reproduce and pass on their genes. So why do humans live so long after reproduction? Many evolutionary psychologists have proposed that living a long life improves the survival of babies because while the parents were out hunting, the grandparents cared for the young.

According to Paul Baltes
Paul Baltes
Paul B. Baltes was a German psychologist whose broad scientific agenda was devoted to establishing and promoting the life-span orientation of human development. He was also a theorist in the field of the psychology of aging...

, the benefits granted by evolutionary selection decrease with age. Natural Selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 has not eliminated many harmful conditions and nonadaptive characteristics that appear among older adults, such as Alzheimer disease. If it were a disease that killed 20 year-olds instead of 70 year-olds this may have been a disease that natural selection could have destroyed ages ago. Thus, unaided by evolutionary pressures against nonadaptive conditions, we suffer the aches, pains, and infirmities of aging. And as the benefits of evolutionary selection decrease with age, the need for culture increases.

Social psychology


As humans are a highly social species, there are many adaptive problems associated with navigating the social world (e.g., maintaining allies, managing hierarchies, interacting with outgroup members). Researchers in the emerging field of evolutionary social psychology have made many discoveries pertaining to topics traditionally studied by social psychologists, including person perception, social cognition, attitudes, emotions, motivation, and cross-cultural differences.

Abnormal psychology


Adaptationist hypotheses regarding the etiology of psychological disorders are often based on analogies between physiological and psychological dysfunctions, as noted in the table below. Evolutionary psychiatrists and psychologists suggest that some mental disorders have multiple causes.

Possible Causes of Psychological 'Abnormalities' from an Adaptationist Perspective

Summary based on information in these textbooks (all titled "Evolutionary Psychology"): Buss (2011), Gaulin & McBurney (2004), Workman & Reader (2008)
Causal mechanism of failure or malfunction of adaptation Physiological Example Hypothesized Psychological Example
Functioning adaptation (adaptive defense) Fever / Vomiting

(functional responses to infection or ingestion of toxins)

Mild depression or anxiety

(functional responses to mild loss or stress)

By-product of an adaptation(s) Intestinal gas

(byproduct of digestion of fiber)

Sexual fetishes (?)

(possible byproduct of normal sexual arousal adaptations that have 'imprinted' on unusual objects or situations)

Adaptations with multiple effects Gene for malaria resistance, in homozygous form, causes sickle cell anemia Adaptation(s) for high levels of creativity may also predispose schizophrenia or bi-polar disorder

(adaptations with both positive and negative effects, perhaps dependent on alternate developmental trajectories)

Malfunctioning adaptation Allergies

(over-reactive immunological responses)

Autism

(possible malfunctioning of theory of mind

Theory of mind
Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires and intentions that are different from one's own...

 module)
Frequency-dependent morphs The two sexes / Different blood and immune system types Personality traits and personality disorders

(may represent alternative behavioral strategies dependent on the frequency of the strategy in the population)

Mismatch between ancestral & current environments Modern diet-related Type 2 Diabetes More frequent modern interaction with strangers (compared to family and close friends) may predispose greater incidence of depression & anxiety
Tails of normal (bell shaped) curve Very short or tall height Tails of the distribution of personality traits (e.g., extremely introverted or extroverted)


Evolutionary psychologists have suggested that schizophrenia and bipolar disorder may reflect a side-effect of genes with fitness benefits, such as increased creativity. (Some individuals with bipolar disorder are especially creative during their manic phases and the close relatives of schizophrenics have been found to be more likely to have creative professions.) A 1994 report by the American Psychiatry Association found that people suffered from schizophrenia at roughly the same rate in Western and non-Western cultures, and in industrialized and pastoral societies, suggesting that schizophrenia is not a disease of civilization nor an arbitrary social invention. Likewise sociopathy may represent an evolutionarily stable strategy, by which a small number of people who cheat on social contracts benefit in a society consisting mostly of non-sociopaths.

These speculations have yet to be developed into fully testable hypotheses, and a great deal of research is required to confirm their validity. Clinical psychology and psychiatry are relatively isolated from the field of evolutionary psychology and the etiological speculations of evolutionary psychology have yet to pass the scrutiny and demanding research criteria of these larger disciplines. Psychiatrists raise the concern that evolutionary psychologists seek to explain hidden adaptive advantages without engaging the rigorous empirical testing required to back up such claims. While there is strong research to suggest a genetic link to bipolar disorder and schizophrenia, there is significant debate within clinical psychology about the relative influence and the mediating role of cultural or environmental factors. For example, epidemiological research suggests that different cultural groups may have divergent rates of diagnosis, symptomatology, and expression of mental illnesses. There has also been increasing acknowledgment of culture-bound disorders, which may be viewed as an argument for an environmental versus genetic psychological adaptation. While certain mental disorders may have psychological traits that can be explained as 'adaptive' on an evolutionary scale, these disorders cause afflicted individuals significant emotional and psychological distress and negatively influence the stability of interpersonal relationships and day-to-day adaptive functioning.

Psychology of religion



Adaptationist perspectives on religious belief
Religious belief
Religious belief is a strong belief in a supernatural power or powers that control human destiny. Such a state may relate to the existence, characteristics and worship of a deity or deities, divine intervention in the universe and human life, or values and practices centered on the teachings of a...

 suggest that, like all behavior, religious behaviors are a product of the human brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

. As with all other organ functions, cognition
Cognition
In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...

's functional structure has been argued to have a genetic foundation, and is therefore subject to the effects of natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 and sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

. Like other organs and tissues, this functional structure should be universally shared amongst humans and should have solved important problems of survival and reproduction in ancestral environments. However, evolutionary psychologists remain divided on whether religious belief is more likely a consequence of evolved psychological adaptations, or is a byproduct of other cognitive adaptations.

Initial response


Although the application of adaptationist approaches to studying animal behavior has become standard and uncontroversial, evolutionary psychology has been entangled in the larger philosophical and social science controversies related to the nature versus nurture
Nature versus nurture
The nature versus nurture debate concerns the relative importance of an individual's innate qualities versus personal experiences The nature versus nurture debate concerns the relative importance of an individual's innate qualities ("nature," i.e. nativism, or innatism) versus personal experiences...

 debate. Some of the controversy has been related not to the science itself, but to concerns about its potential political misuse by others. For example, eugenics
Eugenics
Eugenics is the "applied science or the bio-social movement which advocates the use of practices aimed at improving the genetic composition of a population", usually referring to human populations. The origins of the concept of eugenics began with certain interpretations of Mendelian inheritance,...

 and social darwinism
Social Darwinism
Social Darwinism is a term commonly used for theories of society that emerged in England and the United States in the 1870s, seeking to apply the principles of Darwinian evolution to sociology and politics...

 were political philosophies of the early 20th Century that were largely based on the naturalistic fallacy
Naturalistic fallacy
The naturalistic fallacy is often claimed to be a formal fallacy. It was described and named by British philosopher G. E. Moore in his 1903 book Principia Ethica...

 -- the idea that what is natural is necessarily a moral good. Other critics have expressed concerned about EP itself. As an adaptationist, nature-nurture interactionist perspective, it challenged the basic tenets of the predominant paradigm of the social sciences, social constructionism
Social constructionism
Social constructionism and social constructivism are sociological theories of knowledge that consider how social phenomena or objects of consciousness develop in social contexts. A social construction is a concept or practice that is the construct of a particular group...

. This view suggested that biology could be pretty much safely ignored when studying human behavior. The result has been sometimes heated discussions between supporters of these two different theoretical paradigms.

Reductionism and determinism


Some critics view evolutionary psychology as a form of genetic reductionism and genetic determinism
Genetic determinism
Genetic determinism is the belief that genes determine morphological and behavioral traits and do so with little or no influence from environmental factors....

, a common critique being that evolutionary psychology does not address the complexity of individual development and experience and fails to explain the influence of genes on behavior in individual cases. Evolutionary psychologists respond that EP works within a nature-nurture interactionist framework that acknowledges that many psychological adaptations are facultative (sensitive to environmental variations during individual development). EP is generally not focused on proximate analyses of behavior but rather its focus is on the study of distal/ultimate causality (the evolution of psychological adaptations). The field of behavioral genetics is focused on the study of the proximate influence of genes on behavior.

Testability of hypotheses


A frequent critique of the discipline is that the hypotheses of evolutionary psychology are difficult or impossible to adequately test, thus questioning its status as an actual scientific discipline, for example because many current traits probably evolved to serve different functions than they do now. While evolutionary psychology hypotheses are difficult to test, evolutionary psychologists assert that is not impossible. Part of the critique of the scientific base of evolutionary psychology includes a critique of the concept of the Environments of Evolutionary Adaptation (EEA). Some critics have argued that we know so little about the environment in which homo sapiens evolved that explaining specific traits as an adaption to that environment becomes highly speculative. Evolutionary psychologists respond that we do know many things about this environment, including the facts that only women got pregnant, our ancestors were hunter-gatherers that generally lived in small tribes, etc.

Modularity of mind


There is disagreement among evolutionary psychologists concerning the ability and necessity of the computational, and specifically the modular
Modularity of mind
Modularity of mind is the notion that a mind may, at least in part, be composed of separate innate structures which have established evolutionarily developed functional purposes...

, theory of mind to explain the evolutionary adaptation of psychological traits. Evolutionary psychologists proposing alternative, non-computational models of the mind argue that computational theories are no better at explaining biological reality than non-evolutionary psychology. Proponents of computational theories criticize non-computational approaches for their lack of predictions and empirical support and point to computational theories' record of empirically confirmed predictions. Proponents of computational theories also disagree among themselves about the mind's modular structure either as a few generalist modules or as many highly specific modules.

Evolutionary psychology defence


Overall, evolutionary psychologists argue that many of the criticisms leveled against the field are straw men
Straw man
A straw man is a component of an argument and is an informal fallacy based on misrepresentation of an opponent's position, twisting his words or by means of [false] assumptions...

, are based on a incorrect nature vs. nurture dichotomy, or are based on a misunderstandings of the discipline.

See also



  • Behavioural genetics
    Behavioural genetics
    Quantitative human behavioural genetics is a specialisation in the biological field of behaviour genetics that studies the role of genetics in human behaviour employing quantitative-genetic methods. The field is an overlap of quantitative genetics and psychology...

  • Biocultural evolution
    Biocultural evolution
    Biocultural evolution refers to historical evolutionary processes that occur as a result of culture's interaction with biology.-Cultural factors:...

  • Darwinian literary studies
    Darwinian literary studies
    Darwinian Literary Studies is a branch of literary criticism that studies literature in the context of evolution by means of natural selection, including gene-culture coevolution...

  • Ethnic nepotism
    Ethnic nepotism
    Ethnic nepotism describes a human tendency for in-group bias or in-group favouritism applied by nepotism for people with the same ethnicity.- The theory :...

  • Evolutionary developmental psychology
    Evolutionary developmental psychology
    Evolutionary developmental psychology, , is the application of the basic principles of Darwinian evolution, particularly natural selection, to explain contemporary human development...

  • Evolutionary educational psychology
    Evolutionary educational psychology
    Evolutionary educational psychology is the study of the relation between inherent folk knowledge and abilities and accompanying inferential and attributional biases as these influence academic learning in evolutionarily novel cultural contexts, such as schools and the industrial workplace...

  • Evolutionary neuroscience
    Evolutionary neuroscience
    Evolutionary neuroscience is an interdisciplinary scientific research field that studies the evolution of nervous systems. Evolutionary neuroscientists attempt to understand the evolution and natural history of nervous system structure and function. The field draws on concepts and findings from...

  • Evolutionary psychology research groups and centers
    Evolutionary psychology research groups and centers
    The following is a list of evolutionary psychology research groups and centers....

  • Human behavioral ecology
    Human behavioral ecology
    Human behavioral ecology or human evolutionary ecology applies the principles of evolutionary theory and optimization to the study of human behavioral and cultural diversity. HBE examines the adaptive design of traits, behaviors, and life histories of humans in an ecological context...

  • List of evolutionary psychologists
  • Universal Darwinism
    Universal darwinism
    Universal Darwinism refers to a variety of approaches that extend the theory of Darwinism beyond its original domain of biological evolution on Earth...


Further reading



  • Heylighen F.
    Francis Heylighen
    Francis Paul Heylighen is a Belgian cyberneticist, and research professor at the Vrije Universiteit Brussel, the Dutch-speaking Free University of Brussels, where he directs the transdisciplinary research group on "Evolution, Complexity and Cognition".-Biography:Francis Heylighen was born on...

     (2012). "Evolutionary Psychology", in: A. Michalos (ed.): Encyclopedia of Quality of Life Research (Springer, Berlin).

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