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In paleoanthropology, the recent African origin of modern humans, also called the "Out of Africa" theory (OOA), recent single-origin hypothesis (RSOH), replacement hypothesis, or recent African origin model (RAO), is the dominant model of the geographic origin and early migration of
anatomically modern human Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
s (''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
''). It follows the early expansions of hominins out of Africa, accomplished by '' Homo erectus'' and then ''
Homo neanderthalensis Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the ...
''. The model proposes a "single origin" of ''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
'' in the taxonomic sense, precluding
parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and paral ...
in other regions of traits considered anatomically modern, but not precluding multiple admixture between ''H. sapiens'' and archaic humans in Europe and Asia. ''H. sapiens'' most likely developed in the Horn of Africa between 300,000 and 200,000 years ago, although an alternative hypothesis argues that diverse morphological features of ''H. sapiens'' appeared locally in different parts of Africa and converged due to gene flow between different populations within the same period. The "recent African origin" model proposes that all modern non-African populations are substantially descended from populations of ''H. sapiens'' that left Africa after that time. There were at least several "out-of-Africa" dispersals of modern humans, possibly beginning as early as 270,000 years ago, including 215,000 years ago to at least
Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders ...
, and certainly via northern Africa and the Arabian Peninsula about 130,000 to 115,000 years ago. These early waves appear to have mostly died out or retreated by 80,000 years ago..
See als
''Modern humans in China ~80,000 years ago (?)''
Dieneks' Anthropology Blog.
The most significant "recent" wave out of Africa took place about 70,000–50,000 years ago, via the so-called " Southern Route", spreading rapidly along the coast of Asia and reaching Australia by around 65,000–50,000 years ago, (though some researchers question the earlier Australian dates and place the arrival of humans there at 50,000 years ago at earliest, while others have suggested that these first settlers of Australia may represent an older wave before the more significant out of Africa migration and thus not necessarily be ancestral to the region's later inhabitants) while Europe was populated by an early offshoot which settled the Near East and Europe less than 55,000 years ago...
See als
''mtDNA from 55 hunter-gatherers across 35,000 years in Europe''
Dienekes' Anthroplogy Bog.
In the 2010s, studies in
population genetics Population genetics is a subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as Adaptation (biology), adaptation, ...
uncovered evidence of
interbreeding In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in ...
that occurred between ''H. sapiens'' and archaic humans in Eurasia, Oceania and Africa, indicating that modern population groups, while mostly derived from early ''H. sapiens'', are to a lesser extent also descended from regional variants of archaic humans.


Proposed waves

"Recent African origin," or ''Out of Africa II'', refers to the migration of
anatomically modern humans Early modern human (EMH) or anatomically modern human (AMH) are terms used to distinguish '' Homo sapiens'' (the only extant Hominina species) that are anatomically consistent with the range of phenotypes seen in contemporary humans from exti ...
(''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
'') out of Africa after their emergence at c. 300,000 to 200,000 years ago, in contrast to " Out of Africa I", which refers to the migration of archaic humans from Africa to Eurasia roughly 1.8 to 0.5 million years ago. Omo-Kibish I (Omo I) from southern Ethiopia is the oldest anatomically modern Homo sapiens skeleton currently known (around 233,000 years old). However, there are even older ''Homo sapiens'' fossils from Jebel Irhoud in Morocco which exhibits a mixture of modern and archaic features at around 315,000 years old. Since the beginning of the 21st century, the picture of "recent single-origin" migrations has become significantly more complex, not only due to the discovery of modern-archaic admixture but also due to the increasing evidence that the "recent out-of-Africa" migration took place in a number of waves spread over a long time period. As of 2010, there were two main accepted dispersal routes for the out-of-Africa migration of early anatomically modern humans: via the "Northern Route" (via Nile Valley and Sinai) and the "Southern Route" via the Bab al Mandab strait. * Posth et al. (2017) suggest that early ''Homo sapiens'', or "another species in Africa closely related to us," might have first migrated out of Africa around 270,000 years ago based on the closer affinity within Neanderthals mitochodrial genomes to ''Homo sapiens'' than Denisovans.; see also . * Fossil evidence also points to an early ''Homo sapiens'' migration with the oldest known fossil coming from
Apidima Cave The Apidima Cave (, ''Spilaio Apidima'') is a complex of five caves four small caves located on the western shore of Mani Peninsula in Southern Greece. A systematic investigation of the cave has yielded Neanderthal and ''Homo sapiens'' fossils f ...
in Greece and dated at 210,000 years ago. Finds at Misliya cave, which include a partial jawbone with eight teeth, have been dated to around 185,000 years ago. Layers dating from between 250,000 and 140,000 years ago in the same cave contained tools of the Levallois type which could put the date of the first migration even earlier if the tools can be associated with the modern human jawbone finds. * An eastward dispersal from Northeast Africa to Arabia 150,000–130,000 years ago is based on the stone tools finds at
Jebel Faya Jebel Faya ( ar, جَبَل ٱلْفَايَة, Jabal Al-Fāyah; FAY-NE1) is an archaeological site and limestone hill or escarpment near Al Madam in the Emirate of Sharjah, the UAE, located about east of the city of Sharjah, and between the s ...
dated to 127,000 years ago (discovered in 2011), although fossil evidence in the area is significantly later at 85,000 years ago. Possibly related to this wave are the finds from Zhirendong cave, Southern China, dated to more than 100,000 years ago. Other evidence of modern human presence in China has been dated to 80,000 years ago. * The most significant out of Africa dispersal took place around 50–70,000 years ago via the so-called Southern Route, either before or after the Toba event, which happened between 69,000 and 77,000 years ago. This dispersal followed the southern coastline of Asia, and reached Australia around 65,000–50,000 years ago, or according to some research, by 50,000 years ago at earliest. Western Asia was "re-occupied" by a different derivation from this wave around 50,000 years ago, and Europe was populated from Western Asia beginning around 43,000 years ago. * describes an additional wave of migration after the southern coastal route, namely a northern migration into Europe at circa 45,000 years ago. However, this possibility is ruled out by and , who argue for a single coastal dispersal, with an early offshoot into Europe.


Northern Route dispersal

Beginning 135,000 years ago, tropical Africa experienced megadroughts which drove humans from the land and towards the sea shores, and forced them to cross over to other continents. Fossils of early ''Homo sapiens'' were found in
Qafzeh Mount Precipice ( he, הר הקפיצה, "''Har HaKfitsa''"; ar, جبل القفزة, "''Jebel al-Qafzeh''", "Mount of the Leap"), also known as Mount of Precipitation, Mount of the Leap of the Lord and Mount Kedumim is located just outside the ...
and Es-Skhul Caves in Israel and have been dated to 80,000 to 120,000 years ago. These humans seem to have either become extinct or retreated back to Africa 70,000 to 80,000 years ago, possibly replaced by southbound Neanderthals escaping the colder regions of ice-age Europe. Hua Liu ''et al.'' analyzed autosomal microsatellite markers dating to about 56,000 years ago. They interpret the
paleontological Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...
fossil as an isolated early offshoot that retracted back to Africa. The discovery of stone tools in the
United Arab Emirates The United Arab Emirates (UAE; ar, اَلْإِمَارَات الْعَرَبِيَة الْمُتَحِدَة ), or simply the Emirates ( ar, الِْإمَارَات ), is a country in Western Asia ( The Middle East). It is located at t ...
in 2011 at the Faya-1 site in
Mleiha Mleiha, also Mileiha or Malaihah ( ar, ملَيْحَة), is a town in the Emirate of Sharjah, the United Arab Emirates (UAE) with a population of 4,768 (2015), located some south of the inland Sharjah town of Dhaid. It is the location of archa ...
,
Sharjah Sharjah (; ar, ٱلشَّارقَة ', Gulf Arabic: ''aš-Šārja'') is the third-most populous city in the United Arab Emirates, after Dubai and Abu Dhabi, forming part of the Dubai-Sharjah-Ajman metropolitan area. Sharjah is the capital ...
, indicated the presence of modern humans at least 125,000 years ago, leading to a resurgence of the "long-neglected" North African route. This new understanding of the role of the Arabian dispersal began to change following results from archaeological and genetic studies stressing the importance of southern Arabia as a corridor for human expansions out of Africa. In
Oman Oman ( ; ar, عُمَان ' ), officially the Sultanate of Oman ( ar, سلْطنةُ عُمان ), is an Arabian country located in southwestern Asia. It is situated on the southeastern coast of the Arabian Peninsula, and spans the mouth of ...
, a site was discovered by Bien Joven in 2011 containing more than 100 surface scatters of stone tools belonging to the late Nubian Complex, known previously only from archaeological excavations in the Sudan. Two optically stimulated luminescence age estimates placed the Arabian Nubian Complex at approximately 106,000 years old. This provides evidence for a distinct Stone Age technocomplex in southern Arabia, around the earlier part of the
Marine Isotope Stage 5 Marine Isotope Stage 5 or MIS 5 is a marine isotope stage in the geologic temperature record, between 130,000 and 80,000 years ago. Sub-stage MIS 5e, called the Eemian or Ipswichian, covers the last major interglacial period before the Holocene, w ...
. According to Kuhlwilm and his co-authors,
Neanderthal Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the ...
s contributed genetically to modern humans then living outside of Africa around 100,000 years ago: humans which had already split off from other modern humans around 200,000 years ago, and this early wave of modern humans outside Africa also contributed genetically to the Altai Neanderthals..
See als
''Ancestors of Eastern Neandertals admixed with modern humans 100 thousand years ago''
Dienekes'Anthropology Blog.
They found that "the ancestors of Neanderthals from the Altai Mountains and early modern humans met and interbred, possibly in the Near East, many thousands of years earlier than previously thought". According to co-author Ilan Gronau, "This actually complements archaeological evidence of the presence of early modern humans out of Africa around and before 100,000 years ago by providing the first genetic evidence of such populations." Similar genetic admixture events have been noted in other regions as well.


Southern Route dispersal


Coastal route

By some 50–70,000 years ago, a subset of the bearers of mitochondrial haplogroup L3 migrated from East Africa into the Near East. 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. The group that crossed the Red Sea travelled along the coastal route around
Arabia The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plat ...
and the Persian Plateau to India, which appears to have been the first major settling point. argued for the route along the southern coastline of Asia, across about , reaching Australia by around 50,000 years ago. Today at the Bab-el-Mandeb straits, the
Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...
is about wide, but 50,000 years ago sea levels were lower (owing to glaciation) and the water was much narrower. Though the straits were never completely closed, they were narrow enough to have enabled crossing using simple rafts, and there may have been islands in between. Shell middens 125,000 years old have been found in Eritrea, indicating the diet of early humans included seafood obtained by beachcombing. The dating of the Southern Dispersal is a matter of dispute. It may have happened either pre- or post-Toba, a catastrophic volcanic eruption that took place between 69,000 and 77,000 years ago at the site of present-day Lake Toba. Stone tools discovered below the layers of ash disposed in India may point to a pre-Toba dispersal but the source of the tools is disputed. An indication for post-Toba is haplo-group L3, that originated before the dispersal of humans out of Africa and can be dated to 60,000–70,000 years ago, "suggesting that humanity left Africa a few thousand years after Toba". Some research showing slower than expected genetic mutations in human DNA was published in 2012, indicating a revised dating for the migration to between 90,000 and 130,000 years ago. Some more recent research suggests a migration out-of-Africa of around 50,000-65,000 years ago of the ancestors of modern non-African populations, similar to most previous estimates.


Western Asia

Following the fossils dating 80,000 to 120,000 years ago from
Qafzeh Mount Precipice ( he, הר הקפיצה, "''Har HaKfitsa''"; ar, جبل القفزة, "''Jebel al-Qafzeh''", "Mount of the Leap"), also known as Mount of Precipitation, Mount of the Leap of the Lord and Mount Kedumim is located just outside the ...
and Es-Skhul Caves in Israel there are no ''H. sapiens'' fossils in the
Levant The Levant () is an approximate historical geographical term referring to a large area in the Eastern Mediterranean region of Western Asia. In its narrowest sense, which is in use today in archaeology and other cultural contexts, it is ...
until the Manot 1 fossil from Manot Cave in Israel, dated to 54,700 years ago, though the dating was questioned by . The lack of fossils and stone tool industries that can be safely associated with modern humans in the Levant has been taken to suggest that modern humans were outcompeted by Neanderthals until around 55,000 years ago, who would have placed a barrier on modern human dispersal out of Africa through the Northern Route. Climate reconstructions also support a Southern Route dispersal of modern humans as the
Bab-el-Mandeb The Bab-el-Mandeb ( Arabic: , , ) is a strait between Yemen on the Arabian Peninsula, and Djibouti and Eritrea in the Horn of Africa. It connects the Red Sea to the Gulf of Aden. Name The strait derives its name from the dangers a ...
strait experienced a climate more conductive to human migration than the northern landbridge to the Levant during the major human dispersal out of Africa.


Oceania

It is thought that Australia was inhabited around 65,000–50,000 years ago. As of 2017, the earliest evidence of humans in Australia is at least 65,000 years old, while McChesney stated that Fossils from Lake Mungo, Australia, have been dated to about 42,000 years ago. Other fossils from a site called Madjedbebe have been dated to at least 65,000 years ago., though some researchers doubt this early estimate and date the Madjedbebe fossils at about 50,000 years ago at the oldest. Phylogenetic data suggests that an early Eastern Eurasian lineage trifurcated somewhere in eastern South Asia, and gave rise to the Australo-Papuans, the AASI, as well as East/Southeast Asians, although Australo-Papuans may have also received some gene flow from an earlier group (xOoA), around 2%, next to additional archaic admixture in the Sahul region.Genetics and material culture support repeated expansions into Paleolithic Eurasia from a population hub out of Africa, Vallini et al. 2022 (April 4, 2022) Quote: "''Taken together with a lower bound of the final settlement of Sahul at 37 kya it is reasonable to describe Papuans as either an almost even mixture between East-Eurasians and a lineage basal to West and East-Eurasians which occurred sometimes between 45 and 38kya, or as a sister lineage of East-Eurasians with or without a minor basal OoA or xOoA contribution. We here chose to parsimoniously describe Papuans as a simple sister group of Tianyuan, cautioning that this may be just one out of six equifinal possibilities.''" According to one study, Australo-Papuans (such as the indigenous people of New Guinea and Aboriginal Australians) could have either formed from a mixture between an East Eurasian lineage and lineage basal to West and East Asians, or as a sister lineage of East Asians with or without a minor basal OoA or xOoA contribution. A Holocene hunter-gatherer sample (Leang_Panninge) from South Sulawesi was found to be genetically in between East-Eurasians and Australo-Papuans. The sample could be modeled as ~50% Papuan-related and ~50% Basal-East Asian-related (Andamanese Onge or Tianyuan). The authors concluded that Basal-East Asian ancestry was far more widespread and the peopling of Insular Southeast Asia and Oceania was more complex than previously anticipated.


East and Southeast Asia

In China, the Liujiang man () is among the earliest modern humans found in
East Asia East Asia is the eastern region of Asia, which is defined in both Geography, geographical and culture, ethno-cultural terms. The modern State (polity), states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. ...
. The date most commonly attributed to the remains is 67,000 years ago. High rates of variability yielded by various dating techniques carried out by different researchers place the most widely accepted range of dates with 67,000 BP as a minimum, but do not rule out dates as old as 159,000 BP. claim that modern human teeth have been found in China dating to at least 80,000 years ago. Tianyuan man from China has a probable date range between 38,000 and 42,000 years ago, while Liujiang man from the same region has a probable date range between 67,000 and 159,000 years ago. According to 2013 DNA tests, Tianyuan man is related "to many present-day Asians and Native Americans". Tianyuan is similar in
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
to Liujiang man, and some Jōmon period modern humans found in Japan, as well as modern East and Southeast Asians. A 2021 study about the population history of Eastern Eurasia, concluded that distinctive Basal-East Asian (East-Eurasian) ancestry originated in Mainland Southeast Asia at ~50,000BC from a distinct southern Himalayan route, and expanded through multiple migration waves southwards and northwards respectively. Genetic studies concluded that Native Americans descended from a single founding population that initially split from a Basal-East Asian source population in Mainland Southeast Asia around 36,000 years ago, at the same time at which the proper Jōmon people split from Basal-East Asians, either together with Ancestral Native Americans or during a separate expansion wave. They also show that the basal northern and southern Native American branches, to which all other Indigenous peoples belong, diverged around 16,000 years ago. An indigenous American sample from 16,000BC in
Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyomi ...
, which is craniometrically similar to modern Native Americans as well as Paleosiberias, was found to had largely East-Eurasian ancestry and showed high affinity with contemporary East Asians, as well as Jōmon period samples of Japan, confirming that Ancestral Native Americans split from an East-Eurasian source population in Eastern Siberia.


Europe

According to , an early offshoot from the southern dispersal with haplogroup N followed the Nile from East Africa, heading northwards and crossing into
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...
through the Sinai. This group then branched, some moving into Europe and others heading east into Asia. This hypothesis is supported by the relatively late date of the arrival of modern humans in Europe as well as by archaeological and DNA evidence. Based on an analysis of 55 human mitochondrial genomes (mtDNAs) of hunter-gatherers, argue for a "rapid single dispersal of all non-Africans less than 55,000 years ago."


Genetic reconstruction


Mitochondrial haplogroups


Within Africa

The first lineage to branch off from Mitochondrial Eve was L0. This haplogroup is found in high proportions among the San of Southern Africa and the Sandawe of East Africa. It is also found among the
Mbuti The Mbuti people, or Bambuti, are one of several indigenous pygmy groups in the Congo region of Africa. Their languages are Central Sudanic languages and Bantu languages. Subgroups Bambuti are pygmy hunter-gatherers, and are one of the old ...
people. These groups branched off early in human history and have remained relatively genetically isolated since then. Haplogroups L1, L2 and L3 are descendants of L1–L6, and are largely confined to Africa. The macro haplogroups M and N, which are the lineages of the rest of the world outside Africa, descend from L3. L3 is about 70,000 years old, while haplogroups M and N are about 65–55,000 years old. The relationship between such gene trees and demographic history is still debated when applied to dispersals. Of all the lineages present in Africa, the female descendants of only one lineage, mtDNA haplogroup L3, are found outside Africa. If there had been several migrations, one would expect descendants of more than one lineage to be found. L3's female descendants, the M and N haplogroup lineages, are found in very low frequencies in Africa (although haplogroup M1 populations are very ancient and diversified in
North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north ...
and North-east Africa) and appear to be more recent arrivals. A possible explanation is that these mutations occurred in East Africa shortly before the exodus and became the dominant haplogroups thereafter by means of the founder effect. Alternatively, the mutations may have arisen shortly afterwards.


Southern Route and haplogroups M and N

Results from mtDNA collected from aboriginal Malaysians called Orang Asli indicate that the hapologroups M and N share characteristics with original African groups from approximately 85,000 years ago, and share characteristics with sub-haplogroups found in coastal south-east Asian regions, such as Australasia, the Indian subcontinent and throughout continental Asia, which had dispersed and separated from their African progenitor approximately 65,000 years ago. This southern coastal dispersal would have occurred before the dispersal through the Levant approximately 45,000 years ago. 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 thought to have been destroyed by the rise in sea levels during the
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
epoch. Alternatively, a small European founder population that had expressed haplogroup M and N at first, could have lost haplogroup M through random
genetic drift Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...
resulting from a bottleneck (i.e. a founder effect). The group that crossed the Red Sea travelled along the coastal route around
Arabia The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plat ...
and
Persia Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...
until reaching India. Haplogroup M is found in high frequencies along the southern coastal regions of
Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's fifth-most populous country, with a population of almost 243 million people, and has the world's second-lar ...
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. The indigenous people of the Andaman Islands 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 the mainland. They are evidence of the coastal route of early settlers that extends from India to
Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
and Indonesia all the way to eastern
New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torr ...
. Since M is found in high frequencies in highlanders from New Guinea and the Andamanese and New Guineans have dark skin and
Afro-textured hair Afro-textured hair, or kinky hair, is a human hair texture originating from sub-Saharan Africa. Each strand of this hair type grows in a tiny, angle-like helix shape. The overall effect is such that, contrasted with straight, wavy, or curly hai ...
, some scientists think 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. The proportion of haplogroup M increases eastwards from
Arabia The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plat ...
to India; in eastern India, M outnumbers N by a ratio of 3:1. Crossing into Southeast Asia, haplogroup N (mostly in the form of derivatives of its R subclade) reappears as the predominant lineage. M is predominant in East Asia, but amongst
Indigenous Australians Indigenous Australians or Australian First Nations are people with familial heritage from, and membership in, the ethnic groups that lived in Australia before British colonisation. They consist of two distinct groups: the Aboriginal peoples ...
, N is the more common lineage. This haphazard distribution of Haplogroup N from Europe to Australia can be explained by founder effects and population bottlenecks.


Autosomal DNA

A 2002 study of African, European and Asian populations, found greater genetic diversity among Africans than among Eurasians, and that genetic diversity among Eurasians is largely a subset of that among Africans, supporting the out of Africa model. A large study by Coop ''et al''. (2009) found evidence for
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
in
autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...
DNA outside of Africa. The study distinguishes non-African sweeps (notably KITLG variants associated with
skin color Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics (inherited from one's biological parents and or individu ...
), West-Eurasian sweeps (
SLC24A5 SLC may refer to: Places * Salt Lake City, Utah * Salt Lake City International Airport, IATA Airport Code Education * Sarah Lawrence College, NY * School Leaving Certificate (Nepal) * St. Lawrence College, Ontario, Canada * Small Learning Com ...
) and East-Asian sweeps ( MC1R, relevant to skin color). Based on this evidence, the study concluded that human populations encountered novel selective pressures as they expanded out of Africa.; summary in MC1R and its relation to skin color had already been discussed by . According to this study, Papua New Guineans continued to be exposed to selection for dark skin color so that, although these groups are distinct from Africans in other places, the allele for dark skin color shared by contemporary Africans, Andamanese and New Guineans is an archaism. suggest
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
. A 2014 study by Gurdasani et al. indicates that the higher genetic diversity in Africa was further increased in some regions by relatively recent Eurasian migrations affecting parts of Africa.


Pathogen DNA

Another promising route towards reconstructing human genetic genealogy is via the JC virus (JCV), a type of human
polyomavirus ''Polyomaviridae'' is a family of viruses whose natural hosts are primarily mammals and birds. As of 2020, there are six recognized genera and 117 species, five of which are unassigned to a genus. 14 species are known to infect humans, while othe ...
which is carried by 70–90 percent of humans and which is usually transmitted vertically, from parents to offspring, suggesting codivergence with human populations. For this reason, JCV has been used as a genetic marker for human evolution and migration. This method does not appear to be reliable for the migration out of Africa, in contrast to human genetics, JCV strains associated with African populations are not basal. From this conclude that either a basal African strain of JCV has become extinct or that the original infection with JCV post-dates the migration from Africa.


Admixture of archaic and modern humans

Evidence for
archaic human A number of varieties of '' Homo'' are grouped into the broad category of archaic humans in the period that precedes and is contemporary to the emergence of the earliest early modern humans (''Homo sapiens'') around 300 ka. Omo-Kibish I (Omo I) f ...
species (descended from ''
Homo heidelbergensis ''Homo heidelbergensis'' (also ''H. sapiens heidelbergensis''), sometimes called Heidelbergs, is an extinct species or subspecies of archaic human which existed during the Middle Pleistocene. It was subsumed as a subspecies of '' H. erectus'' i ...
'') having interbred with modern humans outside of Africa, was discovered in the 2010s. This concerns primarily
Neanderthal Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the ...
admixture in all modern populations except for Sub-Saharan Africans but evidence has also been presented for Denisova hominin admixture in
Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologi ...
(i.e. in
Melanesians Melanesians are the predominant and indigenous inhabitants of Melanesia, in a wide area from Indonesia's New Guinea to as far East as the islands of Vanuatu and Fiji. Most speak either one of the many languages of the Austronesian language f ...
,
Aboriginal Australians Aboriginal Australians are the various Indigenous peoples of the Australian mainland and many of its islands, such as Tasmania, Fraser Island, Hinchinbrook Island, the Tiwi Islands, and Groote Eylandt, but excluding the Torres Strait Isl ...
and some Negritos). The rate of Neanderthal admixture to European and Asian populations as of 2017 has been estimated at between about 2–3%. Archaic admixture in some Sub-Saharan African populations hunter-gatherer groups ( Biaka Pygmies and San), derived from archaic hominins that broke away from the modern human lineage around 700,000 years, was discovered in 2011. The rate of admixture was estimated at 2%. Admixture from archaic hominins of still earlier divergence times, estimated at 1.2 to 1.3 million years ago, was found in Pygmies, Hadza and five Sandawe in 2012. From an analysis of Mucin 7, a highly divergent haplotype that has an estimated coalescence time with other variants around 4.5 million years BP and is specific to African populations is inferred to have been derived from interbreeding between African modern and archaic humans.


Stone tools

In addition to genetic analysis, Petraglia ''et al.'' also examines the small stone tools (
microlith A microlith is a small stone tool usually made of flint or chert and typically a centimetre or so in length and half a centimetre wide. They were made by humans from around 35,000 to 3,000 years ago, across Europe, Africa, Asia and Australia. Th ...
ic materials) from the Indian subcontinent and explains the expansion of population based on the reconstruction of paleoenvironment. He proposed that the stone tools could be dated to 35 ka in South Asia, and the new technology might be influenced by environmental change and population pressure.


History of the theory


Classical paleoanthropology

The cladistic relationship of humans with the African apes was suggested by
Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
after studying the behaviour of African apes, one of which was displayed at the London Zoo. The anatomist
Thomas Huxley Thomas Henry Huxley (4 May 1825 – 29 June 1895) was an English biologist and anthropologist specialising in comparative anatomy. He has become known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution. The stor ...
had also supported the hypothesis and suggested that African apes have a close evolutionary relationship with humans. These views were opposed by the German biologist Ernst Haeckel, who was a proponent of the Out of Asia theory. Haeckel argued that humans were more closely related to the primates of South-east Asia and rejected Darwin's African hypothesis. In the '' Descent of Man'', Darwin speculated that humans had descended from apes, which still had small brains but walked upright, freeing their hands for uses which favoured intelligence; he thought such apes were African: In 1871, there were hardly any human fossils of ancient hominins available. Almost fifty years later, Darwin's speculation was supported when anthropologists began finding fossils of ancient small-brained hominins in several areas of Africa (
list of hominina fossils The following tables give an overview of notable finds of hominin fossils and remains relating to human evolution, beginning with the formation of the tribe Hominini (the divergence of the human and chimpanzee lineages) in the late Miocene, roug ...
). The hypothesis of ''recent'' (as opposed to archaic) African origin developed in the 20th century. The "Recent African origin" of modern humans means "single origin" (monogenism) and has been used in various contexts as an antonym to polygenism. 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, who thought as late as 1962 that ''H. sapiens'' arose five times from ''H. erectus'' in five places.


Multiregional origin hypothesis

The historical alternative to the recent origin model is the multiregional origin of modern humans, initially proposed by Milford Wolpoff in the 1980s. This view proposes that the derivation of anatomically modern human populations from ''H. erectus'' at the beginning of the
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...
1.8 million years BP, has taken place within a continuous world population. The hypothesis necessarily rejects the assumption of an infertility barrier between ancient Eurasian and African populations of ''Homo''. The hypothesis was controversially debated during the late 1980s and the 1990s. The now-current terminology of "recent-origin" and "Out of Africa" became current in the context of this debate in the 1990s. Originally seen as an antithetical alternative to the recent origin model, the multiregional hypothesis in its original "strong" form is obsolete, while its various modified weaker variants have become variants of a view of "recent origin" combined with archaic admixture. Stringer (2014) distinguishes the original or "classic" Multiregional model as having existed from 1984 (its formulation) until 2003, to a "weak" post-2003 variant that has "shifted close to that of the Assimilation Model".


Mitochondrial analyses

In the 1980s, Allan Wilson together with Rebecca L. Cann and
Mark Stoneking Mark Stoneking (born 1 August 1956) is a geneticist currently working as the Group Leader of the Max Planck Institute for Evolutionary Anthropology, of Max Planck Gesellschaft at Leipzig, and Honorary Professor of Biological Anthropology, Universi ...
worked on genetic dating of the matrilineal most recent common ancestor of modern human populations (dubbed " Mitochondrial Eve"). To identify informative
genetic marker A genetic marker is a gene or DNA sequence with a known location on a chromosome that can be used to identify individuals or species. It can be described as a variation (which may arise due to mutation or alteration in the genomic loci) that can be ...
s for tracking human evolutionary history, Wilson concentrated on mitochondrial DNA (mtDNA), passed from mother to child. This DNA material mutates quickly, making it easy to plot changes over relatively short times. With his discovery that human mtDNA is genetically much less diverse than chimpanzee mtDNA, Wilson concluded that modern human populations had diverged recently from a single population while older human species such as
Neanderthal Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the ...
s and '' Homo erectus'' had become extinct. With the advent of
archaeogenetics Archaeogenetics is the study of ancient DNA using various molecular genetic methods and DNA resources. This form of genetic analysis can be applied to human, animal, and plant specimens. Ancient DNA can be extracted from various fossilized specimen ...
in the 1990s, the dating of mitochondrial and Y-chromosomal haplogroups became possible with some confidence. By 1999, estimates ranged around 150,000 years for the mt-MRCA and 60,000 to 70,000 years for the migration out of Africa. From 2000 to 2003, there was controversy about the mitochondrial DNA of " Mungo Man 3" (LM3) and its possible bearing on the multiregional hypothesis. LM3 was found to have more than the expected number of sequence differences when compared to modern human DNA ( CRS). Comparison of the mitochondrial DNA with that of ancient and modern aborigines, led to the conclusion that Mungo Man fell outside the range of genetic variation seen in Aboriginal Australians and was used to support the multiregional origin hypothesis. A reanalysis on LM3 and other ancient specimens from the area published in 2016, showed it to be akin to modern Aboriginal Australian sequences, inconsistent with the results of the earlier study.


Y-chromosome analyses

As current estimates on the male most recent common ancestor ("
Y-chromosomal Adam In human genetics, the Y-chromosomal most recent common ancestor (Y-MRCA, informally known as Y-chromosomal Adam) is the patrilineal most recent common ancestor (MRCA) from whom all currently living humans are descended. He is the most recent mal ...
" or Y-MRCA) converge with estimates for the age of
anatomically modern human Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
s and well predate the Out of Africa migration, geographical origin hypotheses continue to be limited to the African continent. The most basal lineages have been detected in
West West or Occident is one of the four cardinal directions or points of the compass. It is the opposite direction from east and is the direction in which the Sun sets on the Earth. Etymology The word "west" is a Germanic word passed into some ...
, Northwest and
Central Africa Central Africa is a subregion of the African continent comprising various countries according to different definitions. Angola, Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, the Republic of the Congo ...
, suggesting plausibility for the Y-MRCA living in the general region of "Central-Northwest Africa". Another study finds a plausible placement in "the north-western quadrant of the African continent" for the emergence of the A1b haplogroup. The 2013 report of
haplogroup A00 Haplogroup A is a human Y-chromosome DNA haplogroup, which includes all living human Y chromosomes. Bearers of extant sub-clades of haplogroup A are almost exclusively found in Africa (or among descendants of populations which have recently le ...
found among the Mbo people of western present-day
Cameroon Cameroon (; french: Cameroun, ff, Kamerun), officially the Republic of Cameroon (french: République du Cameroun, links=no), is a country in west-central Africa. It is bordered by Nigeria to the west and north; Chad to the northeast; the C ...
is also compatible with this picture. The revision of Y-chromosomal phylogeny since 2011 has affected estimates for the likely geographical origin of Y-MRCA as well as estimates on time depth. By the same reasoning, future discovery of presently-unknown archaic haplogroups in living people would again lead to such revisions. In particular, the possible presence of between 1% and 4% Neanderthal-derived DNA in Eurasian genomes implies that the (unlikely) event of a discovery of a single living Eurasian male exhibiting a Neanderthal patrilineal line would immediately push back T-MRCA ("time to MRCA") to at least twice its current estimate. However, the discovery of a Neanderthal Y-chromosome by Mendez ''et al''. A 2016 study suggests the extinction of Neanderthal patrilineages, as the lineage inferred from the Neanderthal sequence is outside of the range of contemporary human genetic variation. Questions of geographical origin would become part of the debate on Neanderthal evolution from '' Homo erectus''.


See also

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Notes


References


Sources

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Further reading

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External links

* Encyclopædia Britannica,
Human Evolution
'
Human Timeline (Interactive)
Smithsonian,
National Museum of Natural History The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7 ...
(August 2016).
Age constraints for the Trachilos footprints from Crete
-
Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...
(October 2021). {{Portal bar, Evolutionary biology Prehistoric migrations Human evolution Human mitochondrial genetics Human genetic history