A
dominance hierarchy (in humans:
social hierarchySocial hierarchy is a multi-tiered pyramid-like social or functional structure having an apex as the centralization of power. The term can also be applied to animal societies, but the term dominance hierarchy is preferred most times...
) is the organization of individuals in a group that occurs when competition for resources leads to aggression. Schjelderup-Ebbe, who studied the often-cited example of the
pecking orderPecking order or just peck order is a hierarchical system of social organization in animals. It was first described from the behaviour of poultry by Thorleif Schjelderup-Ebbe in 1921 under the German terms Hackordnung or Hackliste and introduced into English in 1925. The original usage of "peck...
in chickens, found that such social structures lead to more stable flocks with reduced aggression among individuals.
Dominance hierarchies can be despotic or
linearThe word linear comes from the Latin word linearis, which means created by lines.In mathematics, a linear map or function f is a function which satisfies the following two properties......
. In a despotic hierarchy, only one individual is dominant, while the others are all equally submissive. In a linear hierarchy, for example, in the above cited
pecking orderPecking order or just peck order is a hierarchical system of social organization in animals. It was first described from the behaviour of poultry by Thorleif Schjelderup-Ebbe in 1921 under the German terms Hackordnung or Hackliste and introduced into English in 1925. The original usage of "peck...
of chickens, each individual dominates all individuals below him and not those above him.
Dominance
hierarchiesA hierarchy is an arrangement of items in which the items are represented as being "above," "below," or "at the same level as" one another and with only one "neighbor" above and below each level. These classifications are made with regard to rank, importance, seniority, power status or authority...
occur in most social animal species, including primates who normally live in groups. Dominance hierarchies have been extensively studied in
fishA fish is any aquatic vertebrate animal that is typically ectothermic , covered with scales, and equipped with two sets of paired fins and several unpaired fins...
, birds, and mammals. Dominance hierarchies can be simple linear structures, which often arise from the physical differences among individuals in a group in relation to their access to resources. They are also influenced by the complex social interactions among individuals in the group.
Mechanisms that regulate the formation of hierarchies in animals
The most basic interaction that establishes a Dominance Hierarchy is the dyad, or paired interaction among individuals. To study the formation of hierarchies, scientists have often used the dyadic method, in which two individuals are forced to interact isolated from others. All individuals in the group are paired with each other (i.e. a
round-robinA round-robin tournament or all-play-all tournament is a type of tournament "in which each contestant meets every other contestant in turn". In a single round-robin schedule, each participant plays every other participant once. If each participant plays all others twice, this is frequently called a...
), in isolation, until a hierarchy can be deduced. The process of deducing the hierarchy involves the construction of a dominance matrix, in which wins/ties are expressed in relation to each fish in the group.
Recently, it has been postulated that paired interactions alone can not account for the emergence of dominance hierarchies. This is because in nature, such paired interactions rarely occur in isolation. Thus, a relatively new concept has now emerged in animal behavior: the study of socially-embedded dyads. Such phenomena as the
audience effectThe audience effect is the impact that a passive audience has on a subject performing a task. It was first formally noted in various psychology studies in the early 20th century...
, the context-dependent audience effect in Betta fish (
Betta splendens), the observer effect, and the winner-loser effect, may play important roles in the formation of dominance hierarchies in social groups. Furthermore, it has been argued that the social group forms a complex signaling network: interactions that occur among just two individuals of the group are in turn affected by other signals transmitted by individuals in direct communication with them. In many animals, these putative signals can include postural changes, as well as changes in “state” (such as color changes).
Primates
Dominance hierarchies, though often more subtle, can be observed in human societies and are important for understanding the organization of
familyFamily denotes a group of people or animals affiliated by a consanguinity, affinity or co-residence...
,
tribeA tribe, viewed historically or developmentally, consists of a social group existing before the development of, or outside of, states.Many anthropologists use the term to refer to societies organized largely on the basis of kinship, especially corporate descent groups .Some theorists hold that...
or
clanA clan is a group of people united by kinship and descent, which is defined by actual or perceived descent from a common ancestor. Even if actual lineage patterns are unknown, clan members may nonetheless recognize a founding member or apical ancestor...
, work organizations,
politicsPolitics is a process by which groups of people make decisions. The term is generally applied to behavior within civil governments, but politics has been observed in all human group interactions, including corporate, academic and religious institutions...
, etc. in normal and abnormal social situations. It is not clear how much of dominance hierarchy in humans is due to the
intrinsic biologyThe nature versus nurture debates concern the relative importance of an individual's innate qualities versus personal experiences The nature versus nurture debates concern the relative importance of an individual's innate qualities ("nature", i.e. nativism, or innatism) versus personal experiences...
of our brains, derived from
evolutionIn biology, evolution is change in the genetic material of a population of organisms from one generation to the next. Though changes produced in any one generation are normally small, differences accumulate with each generation and can, over time, cause substantial changes in the population, a...
, and how much is due to
culturalCulture is a term that has different 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...
factors.
Dominance relationships require the cooperation of both parties. The dominant party tacitly agrees not to kill or injure the submissive party provided the submitter concedes and does not interfere with the dominant party's access to resources or compete for mates. The ability to identify and remember members of the group along with their dominance status is also necessary. These hierarchies may have developed, in evolutionary terms, for efficiency and to reduce the likelihood of injury among group members who may share
genesThe 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...
. As with the case of
altruism in animalsAltruism is a well-documented animal behaviour, which appears most obviously in kin relationships but may also be evident amongst wider social groups....
, the voluntary abbreviation of hostilities into symbolic form remains something of a
Darwinian PuzzleA Darwinian puzzle is a trait that appears to reduce the fitness of individuals that possess it. Such traits attract the attention of evolutionary biologists...
.
Individuals with greater hierarchical status tend to displace those ranked lower from access to space, to
foodFood is any substance, usually composed of carbohydrates, fats, proteins and water, that can be eaten or drunk by an animal, including humans, for nutrition or pleasure. Items considered food may be sourced from plants, animals or other categories such as fungus or fermented products like alcohol...
and to
matingIn biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation and, in social animals, also to raise their offspring. For animals, mating methods include random mating, disassortative mating, assortative mating, or a mating pool....
opportunities. Thus, individuals with higher
social statusIn sociology or anthropology, social status is the honor or prestige attached to one's position in society .A society's stratification system, which is the system of distributing rewards to the members of society, determines social status. Social status, the position or rank of a person or group...
tend to have greater
reproductive successReproductive success is defined as the passing of genes onto the next generation in a way that they too can pass those genes on. In practice, this is often a tally of the number of offspring produced by an individual. A more correct definition, which incorporates inclusive fitness, is the...
by mating more often and having more resources to invest in the survival of
offspringIn biology, offspring is the product of reproduction, a new organism produced by one or more parents.Collective offspring may be known as a brood or progeny in a more general way...
.
Hence it serves as an intrinsic factor for population control, insuring adequate resources for the dominant individuals and thus preventing widespread starvation.
TerritorialIn ethology, sociobiology and behavioral ecology, the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
behaviorEthology is the scientific study of animal behavior, and a sub-topic of zoology....
enhances this effect.
These hierarchies are not fixed and depend on any number of changing factors, among them are
ageAgeing or aging is the accumulation of changes in an organism or object over time. Ageing in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of ageing grow and expand over time, while others decline...
,
genderGender commonly refers to the set of characteristics that humans perceive as distinguishing between male and female entities, extending from one's biological sex to, in humans, one's social role or gender identity. As a term, "gender" has more than one valid definition...
, body size, intelligence, and aggressiveness. Status may also be affected by the ability to marshal the support of others. Indeed, the need to maintain social position and social knowledge may be an impetus for the evolution of larger
brainThe brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all...
s in humans and other animals.
Evolution of female dominance
Female dominance is a very rare social structure in mammals, and it is only observed consistently in
hyenaThe Hyaenidae is a mammalian family of order Carnivora. The Hyaenidae family, native to both African and Asian continents, consists of four living species, the Striped Hyena and Brown Hyena , the Spotted Hyena , and the Aardwolf .-Evolution:Hyenas seem to have originated 26 million years ago from...
s and
lemurA lemur is a member of the biological infraorder Lemuriformes, a prosimian and strepsirrhine primate that is endemic to the island of Madagascar. The term "lemur" is derived from the Latin word lemures, meaning "spirits of the night" or "haunter". This likely refers to their large, reflective eyes...
s. It occurs when all adult males exhibit submissive behavior to adult females in social settings. These social settings are usually related to feeding, grooming, and sleeping site priority.
There are three basic proposals for the evolution of female dominance:
- The Energy Conservation Hypothesis: males subordinate to females to conserve energy for intense male-male competition experienced during very short breeding seasons
- Male behavioral strategy: males defer as a parental investment because it ensures more resources in a harsh unpredictable climate for the female, and thus, the male's future offspring.
- Female behavioral strategy: dominance helps females deal with the unusually high reproductive demands; they prevail in more social conflicts because they have more at stake in terms of fitness.
Since these original proposals, scientists like Peter Kappeler have modified and integrated other ideas. However, in the case of lemurs, there is no single hypothesis that can fully explain female
social dominanceSocial dominance orientation , is a personality variable which predicts social and political attitudes. It is a widely applied Social Psychological scale. SDO is conceptualised as a measure of individual differences in levels of group-based discrimination and domination; that is, it is a measure...
at this time and all three are likely to play a role.
See also
- Sociobiology
Sociobiology is a synthesis of scientific disciplines which attempts to explain social behavior in animal species by considering the Darwinian advantages specific behaviors may have. It is often considered a branch of biology and sociology, but also draws from ethology, anthropology, evolution,...
- Social organization
- Hypergamy
Hypergamy is the act or practice of seeking a spouse of equal or higher socio-economic status, or caste status than oneself....
- Organizational hierarchy
- Evolution of intelligence
- Pecking order
Pecking order or just peck order is a hierarchical system of social organization in animals. It was first described from the behaviour of poultry by Thorleif Schjelderup-Ebbe in 1921 under the German terms Hackordnung or Hackliste and introduced into English in 1925. The original usage of "peck...
Books with this theme
- Lord of the Flies
Lord of the Flies is an allegorical novel by Nobel Prize-winning author William Golding. It discusses how culture created by man fails, using as an example a group of British schoolboys stuck on a deserted island who try to govern themselves, but with disastrous results...
by William GoldingSir William Gerald Golding was a British novelist, poet and Nobel Prize for Literature laureate best known for his novel Lord of the Flies...
- Life of Pi
Life of Pi is a fantasy adventure novel written by Canadian author Yann Martel. In the story, the protagonist Piscine "Pi" Molitor Patel, an Indian boy from Pondicherry, explores issues of spirituality and practicality from an early age...
by Yann MartelYann Martel is a Spanish-born Canadian author best known for the Man Booker Prize-winning novel Life of Pi.-Early life:...