Recent African origin of modern humans
Encyclopedia
In 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:...

, the recent African origin of modern humans is the most widely accepted model describing the origin and early dispersal
Early human migrations
Early human migrations began when Homo erectus first migrated out of Africa over the Levantine corridor and Horn of Africa to Eurasia about 1.8 million years ago, a migration probably sparked by the development of language Early human migrations began when Homo erectus first migrated out of Africa...

 of anatomically modern humans
Anatomically modern humans
The term anatomically modern humans in paleoanthropology refers to early individuals of Homo sapiens with an appearance consistent with the range of phenotypes in modern humans....

. The theory is called the (Recent) Out-of-Africa model in the popular press, and academically the recent single-origin hypothesis (RSOH), Replacement Hypothesis, and Recent African Origin (RAO) model. The hypothesis that humans have a single origin (monogenesis) was published 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 Descent of Man (1871). The concept was speculative until the 1980s, when it was corroborated by a study of present-day mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

, combined with evidence based on physical anthropology
Physical anthropology
Biological anthropology is that branch of anthropology that studies the physical development of the human species. It plays an important part in paleoanthropology and in forensic anthropology...

 of archaic specimens.

Genetic and fossil evidence is interpreted to show that archaic Homo sapiens
Archaic Homo sapiens
Archaic Homo sapiens is a loosely defined term used to describe a number of varieties of Homo, as opposed to anatomically modern humans , in the period beginning 500,000 years ago....

 evolved to anatomically modern humans
Anatomically modern humans
The term anatomically modern humans in paleoanthropology refers to early individuals of Homo sapiens with an appearance consistent with the range of phenotypes in modern humans....

 solely in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, between 200,000 and 150,000 years ago, that members of one branch of Homo sapiens left Africa by between 125,000 and 60,000 years ago, and that over time these humans replaced earlier human populations such as Neanderthals and Homo erectus
Homo erectus
Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...

. The date of the earliest successful "out of Africa" migration (earliest migrants with living descendents) has generally been placed at 60,000 years ago as suggested by genetics, although attempts at migration out of the continent may have taken place as early as 125,000 years ago according to Arabian archaeology finds of tools in the region.

The recent single origin of modern humans in East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...

 is the predominant position held within the scientific community. There are differing theories on whether there was a single exodus or several. A multiple dispersal model involves the Southern Dispersal theory, which has gained support in recent years from genetic, linguistic and archaeological evidence. A growing number of researchers also suspect that "long-neglected North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...

", was the original home of the modern humans who first trekked out of the continent.

The major competing hypothesis is the multiregional origin of modern humans
Multiregional origin of modern humans
The multiregional hypothesis is a scientific model that provides an explanation for the pattern of human evolution. The hypothesis holds that humans first arose near the beginning of the Pleistocene two million years ago and subsequent human evolution has been within a single, continuous human...

, which envisions a wave of Homo sapiens migrating from Africa and interbreeding with local Homo erectus
Homo erectus
Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...

populations in multiple regions of the globe. Most multiregionalists still view Africa as a major wellspring of human genetic diversity, but allow a much greater role for hybridization.

History of the theory

With the development of anthropology
History of anthropology
This article mainly discusses 18th- and 19th-century precursors of modern anthropology. For more information on modern social and cultural anthropology as they have developed in Britain, France, and North America since approximately 1900, see the relevant sections under Anthropology.-Overview:The...

 in the early 19th century, scholars disagreed vigorously about different theories of human development. Those such as Johann Friedrich Blumenbach
Johann Friedrich Blumenbach
Johann Friedrich Blumenbach was a German physician, physiologist and anthropologist, one of the first to explore the study of mankind as an aspect of natural history, whose teachings in comparative anatomy were applied to classification of what he called human races, of which he determined...

 and James Cowles Pritchard held that since the creation, the various human races had developed as different varieties sharing descent from one people (monogenism
Monogenesis
Monogenism is the theory of human origins which posits a single origin for all human races. For the belief that all humans are descended from Adam, see Polygenism.Monogenesis may refer to:* Recent African origin of modern humans...

). Their opponents, such as Louis Agassiz
Louis Agassiz
Jean Louis Rodolphe Agassiz was a Swiss paleontologist, glaciologist, geologist and a prominent innovator in the study of the Earth's natural history. He grew up in Switzerland and became a professor of natural history at University of Neuchâtel...

 and Josiah C. Nott
Josiah C. Nott
Josiah Clark Nott was an American physician and surgeon. He was also an author of surgical, yellow fever, and race theories.-Biography:...

, argued for polygenism
Polygenism
Polygenism is a theory of human origins positing that the human races are of different lineages . This is opposite to the idea of monogenism, which posits a single origin of humanity.- Origins :...

, or the separate development of human races as separate species or had developed as separate species through transmutation of species
Transmutation of species
Transmutation of species was a term used by Jean Baptiste Lamarck in 1809 for his theory that described the altering of one species into another, and the term is often used to describe 19th century evolutionary ideas that preceded Charles Darwin's theory of natural selection...

 from apes, with no common ancestor.

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...

 was one of the first to propose common descent
Common descent
In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor....

 of living organisms, and among the first to suggest that all humans had in common ancestors who lived in Africa. In the Descent of Man, he speculated that humans had descended from apes which still had small brains but walked upright, freeing their hands for uses which favoured intelligence. Further, he thought such apes were African:
The prediction was insightful, because in 1871 there were hardly any human fossils of ancient hominids available. Almost fifty years later, Darwin's speculation was supported when anthropologists began finding numerous fossils of ancient small-brained hominids in several areas of Africa (list of hominina fossils).

The debate in anthropology had swung in favour of monogenism by the mid-20th century. Isolated proponents of polygenism held forth in the mid-20th century, such as Carleton Coon
Carleton S. Coon
Carleton Stevens Coon, was an American physical anthropologist, Professor of Anthropology at the University of Pennsylvania, lecturer and professor at Harvard, and president of the American Association of Physical Anthropologists.-Biography:Carleton Coon was born in Wakefield, Massachusetts to a...

, who hypothesized as late as 1962 that Homo sapiens arose five times from Homo erectus in five places. The "Recent African origin" of modern humans means "single origin" (monogenism) and has been used in various contexts as an antonym to polygenism. With the advent of archaeogenetics
Archaeogenetics
Archaeogenetics, a term coined by Colin Renfrew, refers to the application of the techniques of molecular population genetics to the study of the human past. This can involve:*the analysis of DNA recovered from archaeological remains, i.e...

 in the 1990s, scientists were able to date the "out of Africa" migration with some confidence.

In 2000, the mitochondrial DNA (mtDNA) sequence of "Mungo Man 3" (LM3) of ancient Australia was published indicating that Mungo Man was an extinct subspecies that diverged before the most recent common ancestor of contemporary humans. The results, if correct, supports the multiregional origin of modern humans
Multiregional origin of modern humans
The multiregional hypothesis is a scientific model that provides an explanation for the pattern of human evolution. The hypothesis holds that humans first arose near the beginning of the Pleistocene two million years ago and subsequent human evolution has been within a single, continuous human...

 hypothesis. This work was later questioned and explained by W. James Peacock, leader of the team who sequenced Mungo man's ancient mtdna.

The question of whether there was inheritance of other typological (not de facto) 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....

subspecies into the Homo sapiens genetic pool is debated.

Early Homo sapiens

Anatomically modern humans originated in Africa about 250,000 years ago. The trend in cranial expansion
Cranial capacity
Cranial capacity is a measure of the volume of the interior of the cranium of those vertebrates who have both a cranium and a brain. The most commonly used unit of measure is the cubic centimetre or cc...

 and the acheulean
Acheulean
Acheulean is the name given to an archaeological industry of stone tool manufacture associated with early humans during the Lower Palaeolithic era across Africa and much of West Asia, South Asia and Europe. Acheulean tools are typically found with Homo erectus remains...

 elaboration of stone tool technologies which occurred between 400,000 years ago and the second interglacial period in the Middle 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 ....

 (around 250,000 years ago) provide evidence for a transition from H. erectus
Homo erectus
Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...

to H. sapiens. In the Recent African Origin (RAO) scenario, migration within and out of Africa eventually replaced the earlier dispersed H. erectus.

Homo sapiens idaltu
Homo sapiens idaltu
Homo sapiens idaltu is an extinct subspecies of Homo sapiens that lived almost 160,000 years ago in Pleistocene Africa. is from the Saho-Afar word meaning "elder or first born"....

, found at site Middle Awash
Middle Awash
The Middle Awash is an archaeological site along the Awash River in Ethiopia's Afar Depression. A number of Pleistocene and late Miocene hominid remains have been found at the site, along with some of the oldest known Olduwan stone artifacts and patches of fire-baked clay, disputed evidence of the...

 in Ethiopia, lived about 160,000 years ago. It is the oldest known anatomically modern human and classified as an extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 subspecies. Fossils of early Homo sapiens were found in Qafzeh cave in Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

 and have been dated to 80,000 to 100,000 years ago. However these humans seem to have either become extinct or retreated back to Africa 70,000 to 80,000 years ago, possibly replaced by south bound Neanderthals escaping the colder regions of ice age Europe. Hua Liu & al. analyzing autosomal microsatellite markers dates to c. 56,000±5,700 years ago mtDNA evidence. He interprets the paleontological fossil of early modern human from Qafzeh cave as an isolated early offshoot that retracted back to Africa.

All other fossils of fully modern humans outside Africa have been dated to more recent times. The oldest well dated fossils found outside Africa are from Lake Mungo, Australia, and have been dated to about 42,000 years ago. The Tianyuan cave
Tianyuan man
Tianyuan man are the remains of one of the earliest modern humans to inhabit eastern Asia. In 2007, researchers found 34 bone fragments belonging to a single individual at the Tianyuan Cave, near Beijing, China...

 remains in Liujiang region China have a probable date range between 38,000 and 42,000 years ago. They are most similar in morphology to Minatogawa Man
Minatogawa Man
The Minatogawa Man is a prehistoric people of Okinawa, Japan, represented by four skeletons and some isolated bones dated between 16,000 and 14,000 years BCE...

, modern humans dated between 17,000 and 19,000 years ago and found on Okinawa Island, Japan. However, others have dated Liujang Man to 111,000 to 139,000 years before the present.

Beginning about 100,000 years ago evidence of more sophisticated technology and artwork begins to emerge and by 50,000 years ago fully modern behaviour
Behavioral modernity
Behavioral modernity is a term used in anthropology, archeology and sociology to refer to a set of traits that distinguish present day humans and their recent ancestors from both living primates and other extinct hominid lineages. It is the point at which Homo sapiens began to demonstrate a...

 becomes more prominent. Stone tools show regular patterns that are reproduced or duplicated with more precision while tools made of bone and antler appear for the first time.

Genetic reconstruction

Two pieces of the human genome
Human genome
The human genome is the genome of Homo sapiens, which is stored on 23 chromosome pairs plus the small mitochondrial DNA. 22 of the 23 chromosomes are autosomal chromosome pairs, while the remaining pair is sex-determining...

 are quite useful in deciphering human history: mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

 and the Y chromosome
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...

. These are the only two parts of the genome that are not shuffled about by the evolutionary mechanisms that generate diversity with each generation: instead, these elements are passed down intact. According to the hypothesis, all people alive today have inherited the same Mitochondria from one woman who lived in Africa about 160,000 years ago she has been named Mitochondrial Eve
Mitochondrial Eve
In the field of human genetics, Mitochondrial Eve refers to the matrilineal "MRCA" . In other words, she was the woman from whom all living humans today descend, on their mother's side, and through the mothers of those mothers and so on, back until all lines converge on one person...

. All men today have inherited their Y chromosomes from a man who lived 140,000 years ago, probably in Africa. He has been named Y-chromosomal Adam
Y-chromosomal Adam
In human genetics, Y-chromosomal Adam is the theoretical most recent common ancestor from whom all living people are descended patrilineally . Many studies report that Y-chromosomal Adam lived as early as around 142,000 years ago and possibly as recently as 60,000 years ago...

. It is now believed that more men participated in the out of Africa exodus of early humans than women based on comparing non-sex-specific chromosomes with sex-specific ones.

Mitochondrial DNA

The first lineage to branch off from Mitochondrial Eve
Mitochondrial Eve
In the field of human genetics, Mitochondrial Eve refers to the matrilineal "MRCA" . In other words, she was the woman from whom all living humans today descend, on their mother's side, and through the mothers of those mothers and so on, back until all lines converge on one person...

 is L0
Haplogroup L0 (mtDNA)
-Distribution:It is found most commonly in the Sub-Saharan Africa. It reaches its highest frequency in the Khoisan people at 73%. Some of the higher frequencies are: Namibia 79%, South Africa 83% and Botswana 100%....

. This haplogroup is found in high proportions among the San of Southern Africa, the Sandawe of East Africa. It is also found among the Mbuti
Mbuti
Mbuti or Bambuti are one of several indigenous pygmy groups in the Congo region of Africa. Their languages belong to the Central Sudanic and also to Bantu languages.-Overview:...

 people.

These groups branched off early in human history and have remained relatively genetically isolated since then. Haplogroups L1
Haplogroup L1 (mtDNA)
In human mitochondrial genetics, Haplogroup L1 is a human mitochondrial DNA haplogroup common in Central and West Africa.-Origin:Haplogroup L1 is believed to have appeared approximately 110,000 to 170,000 years ago...

, L2
Haplogroup L2 (mtDNA)
In human mitochondrial genetics, Haplogroup L2 is a human mitochondrial DNA haplogroup typical of Africa. Its subclade L2a is a somewhat frequent and widespread mtDNA cluster in Africa, as well as in the African diaspora Americans . et al.-Origin:L2 is a common African lineage. It is believed to...

 and L3
Haplogroup L3 (mtDNA)
In human mitochondrial genetics, Haplogroup L3 is a human mitochondrial DNA haplogroup. Haplogroup L3 has played a pivotal role in the history of the human species...

 are descendents of L1-6 and are largely confined to Africa. The macro haplogroups M
Haplogroup M (mtDNA)
In human mitochondrial genetics, Haplogroup M is a human mitochondrial DNA haplogroup. An enormous haplogroup spanning all the continents, the macro-haplogroup M, like its sibling N, is a descendant of haplogroup L3....

 and N
Haplogroup N (mtDNA)
In human mitochondrial genetics, Haplogroup N is a human mitochondrial DNA haplogroup. An enormous haplogroup spanning many continents, the macro-haplogroup N, like its sibling M, is a descendant of haplogroup L3....

, which are the lineages of the rest of the world outside Africa, descend from L3.

Y-chromosomal DNA

The mutations defining macro-haplogroup CT
Haplogroup CT (Y-DNA)
In human genetics, Haplogroup CT is a Y-chromosome haplogroup, defining one of the major lines of common ancestry of humanity along father-to-son male lines.Men within this haplogroup have Y chromosomes with the SNP mutation M168, along with P9.1 and M294...

 (all Y haplogroups except A
Haplogroup A (Y-DNA)
In human genetics, Haplogroup A refers to a group of y-chromosome lineages that were among the first to branch off from the root of the human y-chromosome phylogeny...

 and B
Haplogroup B (Y-DNA)
In human genetics, Haplogroup B is a Y-chromosome haplogroup.-Distribution:Haplogroup B is localized to sub-Saharan Africa, especially to tropical forests of West-Central Africa. After Y-haplogroup A, it is the second oldest and one of the most diverse human Y-haplogroups...

) predate the "Out of Africa" migration, its descendent macro-group DE
Haplogroup DE (Y-DNA)
In human genetics, Haplogroup DE is a human Y-chromosome DNA haplogroup. It is defined by the single nucleotide polymorphism mutations, or UEPs, M1, M145, M203, P144, P153, P165, P167, P183....

 being confined to Africa. The mutations that distinguish Haplogroup C
Haplogroup C (Y-DNA)
In human genetics, Haplogroup C is a Y-chromosome haplogroup, defined by UEPs M130/RPS4Y711, M216, P184, P255, and P260, which are all SNP mutations. It is a sibling clade of Haplogroup F, within the more ancient grouping of Haplogroup CF...

 from all other descendants of CR have occurred some 60,000 years ago, shortly after the first Out of Africa migration.

Haplogroup F originated some 45,000 years ago, either in North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...

 (in which case it would point to a second wave of out-of-Africa migration) or in South Asia
South Asia
South Asia, also known as Southern Asia, is the southern region of the Asian continent, which comprises the sub-Himalayan countries and, for some authorities , also includes the adjoining countries to the west and the east...

. More than 90% of males not native to Africa are descended in direct male line from the first bearer of haplogroup F.

Genomic analysis

Although mitochondrial DNA and Y-chromosomal DNA are particularly useful in deciphering human history, data on the genomes of dozens of population groups have also been studied. In June 2009, an analysis of genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....

-wide SNP data from the International HapMap Project
International HapMap Project
The International HapMap Project is an organization that aims to develop a haplotype map of the human genome, which will describe the common patterns of human genetic variation. HapMap is a key resource for researchers to find genetic variants affecting health, disease and responses to drugs and...

 (Phase II) and CEPH Human Genome Diversity Panel samples was published. Those samples were taken from 1138 unrelated individuals. Before this analysis, population geneticists
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...

 expected to find dramatic differences among ethnic group
Ethnic group
An ethnic group is a group of people whose members identify with each other, through a common heritage, often consisting of a common language, a common culture and/or an ideology that stresses common ancestry or endogamy...

s, with derived allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...

s shared among such groups but uncommon or nonexistent in other groups. Instead the study of 53 populations taken from the HapMap and CEPH data revealed that the population groups studied fell into just three genetic groups: Africans, Eurasians (which includes natives of Europe and the Middle East, and Southwest Asians east to present-day Pakistan), and East Asians, which includes natives of Asia, Japan, Southeast Asia, the Americas, and Oceania. The study determined that most ethnic group differences can be attributed to genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...

, with modern African populations having greater genetic diversity than the other two genetic groups, and modern Eurasians somewhat more than modern East Asians. The study suggested 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....

 may shape the human genome much more slowly than previously thought, with factors such as migration within and among continents more heavily influencing the distribution of genetic variations.

Exodus from Africa

By some 70 millennia ago, a part of the bearers of mitochondrial haplogroup
L3
Haplogroup L3 (mtDNA)
In human mitochondrial genetics, Haplogroup L3 is a human mitochondrial DNA haplogroup. Haplogroup L3 has played a pivotal role in the history of the human species...

  migrated from East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...

 into the Near East
Near East
The Near East is a geographical term that covers different countries for geographers, archeologists, and historians, on the one hand, and for political scientists, economists, and journalists, on the other...

.
The date of this first wave of "out of Africa" migration has been called into question in 2011, based on the discovery of stone tools in the United Arab Emirates
United Arab Emirates
The United Arab Emirates, abbreviated as the UAE, or shortened to "the Emirates", is a state situated in the southeast of the Arabian Peninsula in Western Asia on the Persian Gulf, bordering Oman, and Saudi Arabia, and sharing sea borders with Iraq, Kuwait, Bahrain, Qatar, and Iran.The UAE is a...

, indicating the presence of modern humans between 100,000 and 125,000 years ago.

Some scientists believe that only a few people left Africa in a single migration that went on to populate the rest of the world, based in the fact that only descents of L3
Haplogroup L3 (mtDNA)
In human mitochondrial genetics, Haplogroup L3 is a human mitochondrial DNA haplogroup. Haplogroup L3 has played a pivotal role in the history of the human species...

 are found outside Africa. From that settlement, some others point to the possibility of several waves of expansion. For example, Wells
Spencer Wells
Spencer Wells is a geneticist and anthropologist, an at the National Geographic Society, and Frank H.T. Rhodes Class of '56 Professor at Cornell University. He leads The Genographic Project.-Education:...

 says that the early travelers followed the southern coastline of Asia, crossed about 250 kilometers [155 miles] of sea, and colonized Australia by around 50,000 years ago. The Aborigines of Australia
Australian Aborigines
Australian Aborigines , also called Aboriginal Australians, from the latin ab originem , are people who are indigenous to most of the Australian continentthat is, to mainland Australia and the island of Tasmania...

, Wells says, are the descendants of the first wave of migrations.

It has been estimated that from a population of 2,000 to 5,000 individuals in Africa, only a small group, possibly as few as 150 to 1,000 people, crossed the Red Sea. Of all the lineages present in Africa only the female descendants of one lineage, mtDNA haplogroup L3
Haplogroup L3 (mtDNA)
In human mitochondrial genetics, Haplogroup L3 is a human mitochondrial DNA haplogroup. Haplogroup L3 has played a pivotal role in the history of the human species...

, are found outside Africa. Had there been several migrations one would expect descendants of more than one lineage to be found outside Africa. L3's female descendants, the M
Haplogroup M (mtDNA)
In human mitochondrial genetics, Haplogroup M is a human mitochondrial DNA haplogroup. An enormous haplogroup spanning all the continents, the macro-haplogroup M, like its sibling N, is a descendant of haplogroup L3....

 and N
Haplogroup N (mtDNA)
In human mitochondrial genetics, Haplogroup N is a human mitochondrial DNA haplogroup. An enormous haplogroup spanning many continents, the macro-haplogroup N, like its sibling M, is a descendant of haplogroup L3....

 haplogroup lineages, are found in very low frequencies in Africa (although haplogroup M1 is very ancient and diversified in North
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...

 and Northeast Africa
Horn of Africa
The Horn of Africa is a peninsula in East Africa that juts hundreds of kilometers into the Arabian Sea and lies along the southern side of the Gulf of Aden. It is the easternmost projection of the African continent...

) and appear to be recent arrivals. A possible explanation is that these mutations occurred in East Africa shortly before the exodus and by the founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...

 became the dominant haplogroups after the exodus from Africa. Alternatively, the mutations may have arisen shortly after the exodus from Africa.

Other scientists have proposed a Multiple Dispersal Model, in which there were two migrations out of Africa, one across the Red Sea travelling along the coastal regions to India
South Asia
South Asia, also known as Southern Asia, is the southern region of the Asian continent, which comprises the sub-Himalayan countries and, for some authorities , also includes the adjoining countries to the west and the east...

 (the Coastal Route), which would be represented by Haplogroup M. Another group of migrants with Haplogroup N followed the Nile from East Africa, heading northwards and crossing into Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

 through the Sinai. This group then branched in several directions, some moving into Europe and others heading east into Asia. This hypothesis attempts to explain why Haplogroup N is predominant in Europe and why Haplogroup M is absent in Europe. Evidence of the coastal migration is hypothesized to have been destroyed by the rise in sea levels during the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

 epoch. Alternatively, a small European founder population that initially expressed both Haplogroup M and N could have lost Haplogroup M through random genetic drift resulting from a bottleneck
Population bottleneck
A population bottleneck is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing....

 (i.e. a founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...

).

Today at the Bab-el-Mandeb straits the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...

 is about 12 miles (20 kilometres) wide, but 50,000 years ago sea levels were 70 meters lower (owing to glaciation) and the water was much narrower. Though the straits were never completely closed, there may have been islands in between which could be reached using simple rafts. Shell middens 125,000 years old have been found in Eritrea
Eritrea
Eritrea , officially the State of Eritrea, is a country in the Horn of Africa. Eritrea derives it's name from the Greek word Erethria, meaning 'red land'. The capital is Asmara. It is bordered by Sudan in the west, Ethiopia in the south, and Djibouti in the southeast...

, indicating the diet of early humans included seafood obtained by beachcombing
Beachcombing
Beachcombing and beachcomber are words with multiple, but related, meanings that have evolved over time.A beachcomber is someone who "combs" the beach, and the intertidal zone in general, looking for things of value, interest or utility....

.

Subsequent expansion

From the Near East, these populations spread east to South Asia by 50,000 years ago, and on to Australia by 40,000 years ago, Homo sapiens for the first time colonizing territory never reached by Homo erectus. Europe
Paleolithic Europe
Paleolithic Europe refers to the Paleolithic period of Europe, a prehistoric era distinguished by the development of the first stone tools and which covers roughly 99% of human technological history...

 was reached by Cro-Magnon
Cro-Magnon
The Cro-Magnon were the first early modern humans of the European Upper Paleolithic. The earliest known remains of Cro-Magnon-like humans are radiometrically dated to 35,000 years before present....

 some 40,000 years ago. East Asia (Korea
Prehistoric Korea
The Prehistoric Korea is the era of human existence in the Korean Peninsula for which written records did not exist. It, however, constitutes the greatest segment of the Korean past and is the major object of study in the disciplines of archaeology, geology, and...

, Japan
Japanese Paleolithic
The began around 50,000 to 30,000 BC, when the earliest stone tool implements have been found, and continued to around 14,000 BC, at the end of the last ice age, which corresponds to the beginning of the Mesolithic Jōmon period...

) was reached by 30,000 years ago. It is disputed whether subsequent migration to North America
Models of migration to the New World
There have been several models for the human settlement of the Americas proposed by various academic communities. The question of how, when and why humans first entered the Americas is of intense interest to archaeologists and anthropologists, and has been a subject of heated debate for centuries...

 took place around 30,000 years ago, or only considerably later, around 14,000 years ago.

The group that crossed the Red Sea travelled along the coastal route around the coast of Arabia and Persia until reaching India, which appears to be the first major settling point. M is found in high frequencies along the southern coastal regions of Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

 and India and it has the greatest diversity in India, indicating that it is here where the mutation may have occurred. Sixty percent of the Indian population belong to Haplogroup M
Haplogroup M (mtDNA)
In human mitochondrial genetics, Haplogroup M is a human mitochondrial DNA haplogroup. An enormous haplogroup spanning all the continents, the macro-haplogroup M, like its sibling N, is a descendant of haplogroup L3....

. The indigenous people of the Andaman Islands
Andaman Islands
The Andaman Islands are a group of Indian Ocean archipelagic islands in the Bay of Bengal between India to the west, and Burma , to the north and east...

 also belong to the M lineage. The Andamanese are thought to be offshoots of some of the earliest inhabitants in Asia because of their long isolation from mainland Asia. They are evidence of the coastal route of early settlers that extends from India along the coasts of Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...

 and Indonesia all the way to Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...

. Since M is found in high frequencies in highlanders from New Guinea as well, and both the Andamanese and New Guineans have dark skin and Afro-textured hair, some scientists believe they are all part of the same wave of migrants who departed across the Red Sea ~60,000 years ago in the Great Coastal Migration. Notably, the findings of Harding et al. (2000, p. 1355) show that, at least with regard to dark skin color, the haplotype
Haplotype
A haplotype in genetics is a combination of alleles at adjacent locations on the chromosome that are transmitted together...

 background of Papua New Guineans at MC1R (one of a number of genes involved in melanin production) is identical to that of Africans (barring a single silent mutation). Thus, although these groups are distinct from Africans at other loci (due to drift, bottlenecks, etc.), it is evident that selection for the dark skin color trait likely continued (at least at MC1R) following the exodus. This would support the hypothesis that suggests that the original migrants from Africa resembled pre-exodus Africans (at least in skin color), and that the present day remnants of this ancient phenotype can be seen among contemporary Africans, Andamanese and New Guineans. Others suggest that their physical resemblance to Africans could be the result of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

.

From Arabia to India the proportion of haplogroup M increases eastwards: in eastern India, M outnumbers N by a ratio of 3:1. However, crossing over into East Asia, Haplogroup N reappears as the dominant lineage. M is predominant in South East Asia but amongst Indigenous Australians
Indigenous Australians
Indigenous Australians are the original inhabitants of the Australian continent and nearby islands. The Aboriginal Indigenous Australians migrated from the Indian continent around 75,000 to 100,000 years ago....

 N reemerges as the more common lineage. This discontinuous distribution of Haplogroup N from Europe to Australia can be explained by founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...

s and population bottleneck
Population bottleneck
A population bottleneck is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing....

s.

Competing hypotheses

The multiregional hypothesis, initially proposed by Milford Wolpoff, holds that the evolution of humans from H. erectus at the beginning 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 BP to the present day has been within a single, continuous worldwide population. Proponents of multiregional origin reject the assumption of an infertility barrier between ancient Eurasian and African populations of Homo. Multiregional proponents point to the fossil record and genetic evidence in chromosomal DNA. One study suggested that at least 5% of the human modern gene pool can be attributed to ancient admixture, which in Europe would be from the Neanderthal
Neanderthal
The Neanderthal is an extinct member of the Homo genus known from Pleistocene specimens found in Europe and parts of western and central Asia...

s. But the study also suggests that there may be other reasons why humans and Neanderthals share ancient genetic lineages.

The strong form of the theory has been further challenged by recent genetic discoveries regarding the non-Homo sapiens Denisova hominin
Denisova hominin
Denisova hominins , or Denisovans, are Paleolithic-Era members of the genus Homo that may belong to a previously unknown species. In , scientists announced the discovery of a finger bone fragment of a juvenile female that lived about 41,000 years ago, found in Denisova Cave in Altai Krai, Russia, a...

, known from only one sample in Siberia. The sample was found to share 4–6% genetic affinities with modern Melanesians
Melanesians
Melanesians are an ethnic group in Melanesia. The original inhabitants of the group of islands now named Melanesia were likely the ancestors of the present-day Papuan-speaking people...

, but not with other extant groups, making hybridisation in Africa very unlikely in this case.

Other hypothesis see the emergence of Homo erectus outside Africa (in Eurasia) and then returning to colonize that continent from which his ancestors originated.

See also

  • Hofmeyr Skull
    Hofmeyr Skull
    The Hofmeyr Skull is a specimen of a 37,000 year old human skull found in 1952. It is one of the very few modern human skulls discovered in Africa south of Ethiopia and older than 20,000 years.-Background:...

  • Identical ancestors point
    Identical ancestors point
    In genetic genealogy, the identical ancestors point is that point in a given population's past where each individual then alive turned out to be either the ancestor of every individual alive now, or to have no living descendants at all...

  • Sahara pump theory
    Sahara pump theory
    The Sahara pump theory is a hypothesis that explains how flora and fauna migrated between Eurasia and Africa via a Levantine land bridge. The theory observes that extended periods of abundant rainfall lasting many thousands of years in Africa are associated with a "wet Sahara" phase, during which...

  • Toba catastrophe theory
    Toba catastrophe theory
    The Toba supereruption was a supervolcanic eruption that occurred some time between 69,000 and 77,000 years ago at Lake Toba . It is recognized as one of the Earth's largest known eruptions...

  • Behavioral modernity
    Behavioral modernity
    Behavioral modernity is a term used in anthropology, archeology and sociology to refer to a set of traits that distinguish present day humans and their recent ancestors from both living primates and other extinct hominid lineages. It is the point at which Homo sapiens began to demonstrate a...

  • Archaeogenetics of the Near East
    Archaeogenetics of the Near East
    The archaeogenetics of the Near East involves the study of aDNA or ancient DNA, identifying haplogroups and haplotypes of ancient skeletal remains from both YDNA and mtDNA for populations of the Ancient Near East The archaeogenetics of the Near East involves the study of aDNA or ancient DNA,...

  • Genetics and archaeogenetics of South Asia
    Genetics and archaeogenetics of South Asia
    The study of the genetics and archaeogenetics of the ethnic groups of South Asia aims at uncovering these groups' genetic history. The geographic position of India makes Indian populations important for the study of the early dispersal of all human populations on the Eurasian continent.The Indian...


  • Genetic history of Europe
    Genetic history of Europe
    The genetic history of Europe can be inferred from the patterns of genetic diversity across continents and time. The primary data to develop historical scenarios coming from sequences of mitochondrial, Y-chromosome and autosomal DNA from modern populations and if available from ancient DNA...

  • Genetic history of Italy
    Genetic history of Italy
    During prehistory Italy was populated by different but very similar Indo-European groups, later collectively listed amongst the Ancient peoples of Italy, of whom the Italic one was predominant....

  • Genetic history of North Africa
    Genetic history of North Africa
    The population genetics of North Africans has been heavily influenced by geography.The Sahara desert to the south and the Mediterranean Sea to the North were important barriers to gene flow in prehistoric times. However Eurasia and Africa form a single land mass at the Suez. At the Straits of...

  • Genetic history of indigenous peoples of the Americas
  • Genetic history of the Iberian Peninsula
    Genetic history of the Iberian Peninsula
    The ancestry of modern Iberians is consistent with the geographical situation of the Iberian Peninsula in the south-west of Europe: there are strong connections with both Mediterranean Europe and Atlantic Europe....

  • Genetic history of the British Isles
    Genetic history of the British Isles
    The genetic history of the British Isles is the subject of research within the larger field of human population genetics. It has developed in parallel with DNA testing technologies capable of identifying genetic similarities and differences between populations...


Further reading



External links


Documentaries
  • DNA Mysteries – The Search for Adam – by Spencer Wells – National Geographic, 2008
  • The Real Eve: Modern Man's Journey Out of Africa – by Stephen Oppenheimer
    Stephen Oppenheimer
    Stephen Oppenheimer is a British paediatrician, geneticist, and writer. He is a member of Green Templeton College, Oxford and an honorary fellow of Liverpool School of Tropical Medicine, and carries out and publishes research in the fields of genetics and human prehistory.-Career:Oppenheimer...

     – Discovery Channel
    Discovery Channel
    Discovery Channel is an American satellite and cable specialty channel , founded by John Hendricks and distributed by Discovery Communications. It is a publicly traded company run by CEO David Zaslav...

    , 2002
  • Journey of Man: A Genetic Odyssey (movie) by Spencer Wells – PBS and National Geographic Channel
    National Geographic Channel
    National Geographic Channel, also commercially abbreviated and trademarked as Nat Geo, is a subscription television channel that airs non-fiction television programs produced by the National Geographic Society. Like History and the Discovery Channel, the channel features documentaries with factual...

    , 2003
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