Therecent African origin of modern humans or the "Out of Africa"theory (OOA)[a] holds that present-day humans outside Africa descend mainly from a single expansion ofanatomically modern humans (Homo sapiens) from Africa about 70,000–50,000 years ago. It is the most widely accepted[1][2][3]paleo-anthropological model of the geographic origin andearly migration of the human species.
The model proposes a "single origin" ofHomo sapiens in thetaxonomic sense, precludingparallel evolution in other regions of traits consideredanatomically modern,[4] but not precluding multipleadmixture betweenH. sapiens andarchaic humans in Europe and Asia.[b][5][6]H. sapiens most likely developed in theHorn of Africa between 300,000 and 200,000 years ago,[7][8] although an alternative hypothesis argues that diverse morphological features ofH. sapiens appeared locally in different parts of Africa and converged due togene flow between different populations within the same period.[9][10] The "recent African origin" model proposes that all modern non-African populations are substantially descended from populations ofH. 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, certainly via northern Africa and the Arabian Peninsula about 130,000 to 115,000 years ago at least.[17] There is evidence that modern humans had reached China around 80,000 years ago.[18][19] Practically all of these early waves seem to have gone extinct or retreated back, and present-day humans outside Africa descend mainly from a single expansion about 70,000–50,000 years ago,[20][21][22][7][8][23][24][excessive citations] via the so-called "Southern Route". These humans spread rapidly along the coast of Asia and reachedAustralia by around 65,000–50,000 years ago,[25][26][c] (though some researchers question the earlier Australian dates and place the arrival of humans there at 50,000 years ago at earliest,[27][28] 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[22]) while Europe was populated by an early offshoot which settled the Near East and Europe less than 55,000 years ago.[29][30][31]
In the 2010s, studies inpopulation genetics uncovered evidence ofinterbreeding that occurred betweenH. sapiens andarchaic humans in Eurasia, Oceania and Africa,[32][33][34] indicating that modern population groups, while mostly derived from earlyH. sapiens, are to a lesser extent also descended from regional variants of archaic humans.
Layer sequence atKsar Akil in theLevantine corridor, and discovery of two fossils ofHomo sapiens, dated to 40,800 to 39,200 years BP for "Egbert",[35] and 42,400–41,700 BP for "Ethelruda".[35]
"Recent African origin", orOut of Africa II, refers to the migration ofanatomically modern humans (Homo sapiens) 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 from before 1.8 and up 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).[36] There are even olderHomo sapiens fossils fromJebel Irhoud in Morocco which exhibit a mixture of modern and archaic features at around 315,000 years old.[37]
Since the beginning of the 21st century, the picture of "recent single-origin" migrations has become significantly more complex, due to the discovery of modern-archaic admixture and the increasing evidence that the "recent out-of-Africa" migration took place in waves over a long time. As of 2010, there were two main accepted dispersal routes for the out-of-Africa migration of early anatomically modern humans, the "Northern Route" (via Nile Valley and Sinai) and the "Southern Route" via theBab-el-Mandeb strait.[38]
Posth et al. (2017) suggest that earlyHomo 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'mitochondrial genomes toHomo sapiens thanDenisovans.[39]
An interpration, with as of yet limited recognition, of a skull fragment coming fromApidima Cave in Greece dated at 210,000 years ago as aHomo sapiens specimen may also points to an earlyHomo sapiens migration.[40] Finds atMisliya cave, which include a partial jawbone with eight teeth, that may belong to aHomo sapiens specimen, 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 theLevallois type which could put the date of the first migration even earlier if the tools can be associated with the modern human jawbone finds.[41][42][43]
An eastward dispersal from Northeast Africa to Arabia 150,000–130,000 years ago is based on the stone tools finds atJebel Faya dated to 127,000 years ago (discovered in 2011), although fossil evidence in the area is significantly later at 85,000 years ago.[11][44] Possibly related to this wave are the finds fromZhirendong cave, Southern China, dated to more than 100,000 years ago.[45] Other evidence of modern human presence in China has been dated to 80,000 years ago.[19]
The most significant out of Africa dispersal took place around 50,000–70,000 years ago via the so-calledSouthern Route, either before[46] or after[30][31] theToba event, which happened between 69,000 and 77,000 years ago.[46] 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.[27][28] 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.[38]
Wells (2003) describes an additional wave of migration after the southern coastal route, a northern migration into Europe about 45,000 years ago.[d] This possibility is ruled out byMacaulay et al. (2005) andPosth et al. (2016), who argue for a single coastal dispersal, with an early offshoot into Europe.
Anatomically Modern Humans known archaeological remains in Europe and Africa, directly dated, calibratedcarbon dates as of 2013.[35]
Beginning 135,000 years ago, tropical Africa experiencedmegadroughts which drove humans from the land and towards the sea shores, and forced them to cross over to other continents.[47][e]
Fossils of earlyHomo sapiens were found inQafzeh andEs-Skhul Caves in Israel and have been dated to 80,000 to 120,000 years ago.[48][49] 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.[20] Hua Liuet al. analyzed autosomal microsatellite markers dating to about 56,000 years ago. They interpret thepaleontological fossil as an isolated early offshoot that retracted back to Africa.[21]
The discovery of stone tools in theUnited Arab Emirates in 2011 at theFaya-1 site inMleiha,Sharjah, indicated the presence of modern humans at least 125,000 years ago,[11] leading to a resurgence of the "long-neglected" North African route.[12][50][13][14] 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.[51]
InOman, 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 fromarchaeological excavations in theSudan. Two optically stimulated luminescence age estimates placed the Arabian Nubian Complex at approximately 106,000 years old. This provides evidence for a distinctStone Age technocomplex in southern Arabia, around the earlier part of theMarine Isotope Stage 5.[52]
According to Kuhlwilm and his co-authors,Neanderthalscontributed 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.[53] They found that "the ancestors of Neanderthals from theAltai Mountains and early modern humans met and interbred, possibly in the Near East, many thousands of years earlier than previously thought".[53] 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."[53] Similargenetic admixture events have beennoted in other regions as well.[54]
By some 50–70,000 years ago, a subset of the bearers of mitochondrial haplogroupL3 migrated fromEast Africa into theNear 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.[55][56] The group that crossed the Red Sea travelled along the coastal route aroundArabia and thePersian Plateau to India, which appears to have been the first major settling point.[57]Wells (2003) argued for the route along the southern coastline of Asia, across about 250 kilometres (155 mi), reaching Australia by around 50,000 years ago.
Migration routes of modern humans, showing the northern route populating Western Eurasia, and the southern/coastal route populating Eastern Eurasia.
Today at theBab-el-Mandeb straits, theRed Sea is about 20 kilometres (12 mi) wide, but 50,000 years ago sea levels were 70 m (230 ft) lower (owing to glaciation) and the water channel 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.[38][58] Shellmiddens 125,000 years old have been found inEritrea,[59] indicating that the diet of early humans included seafood obtained bybeachcombing.
The dating of the Southern Dispersal is a matter of dispute.[46] 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-dayLake Toba in Sumatra, Indonesia. Stone tools discovered below the layers of ash deposited in India may point to a pre-Toba dispersal but the source of the tools is disputed.[46] 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".[46] 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.[60] 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.[22][61][62]
Following the fossils dating 80,000 to 120,000 years ago fromQafzeh andEs-Skhul Caves in Israel there are noH. sapiens fossils in theLevant until theManot 1 fossil fromManot Cave in Israel, dated to 54,700 years ago,[63] though the dating was questioned byGroucutt et al. (2015). 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.[64][failed verification] Climate reconstructions also support a Southern Route dispersal of modern humans as theBab-el-Mandeb strait experienced a climate more conductive to human migration than the northern landbridge to the Levant during the major human dispersal out of Africa.[65]
A 2023 study proposed that Eurasians and Africans genetically diverged ~100,000 years ago. Many Eurasians then lived in the Saudi Peninsula, genetically isolated from at least 85 kya, before expanding north 54 kya. For reference, Homo sapiens and Neanderthals diverged ~500 kya.[66]
Fossils fromLake Mungo, Australia, have been dated to about 42,000 years ago.[67][68] Other fossils from a site calledMadjedbebe have been dated to at least 65,000 years ago,[69][70] though some researchers doubt this early estimate and date the Madjedbebe fossils at about 50,000 years ago at the oldest.[27][28]
Phylogenetic data suggests that an early Eastern Eurasian (Eastern non-African) meta-population trifurcated somewhere ineastern South Asia, and gave rise to the Australo-Papuans, the Ancient Ancestral South Indians (AASI), as well as East/Southeast Asians, although Papuans may have also received some gene flow from an earlier group (xOoA), around 2%,[71] next to additional archaic admixture in theSahul region.[72][73]
According to one study, Papuans 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.[74]
A Holocene hunter-gatherer sample (Leang_Panninge) fromSouth 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.[75][76]
In China, theLiujiang man (Chinese:柳江人) is among the earliest modern humans found inEast Asia.[77] The date most commonly attributed to the remains is 67,000 years ago.[78] 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.[78]Liu, Martinón-Torres et al. (2015) claim that modern human teeth have been found in China dating to at least 80,000 years ago.[79]
Tianyuan man from China has a probable date range between 38,000 and 42,000 years ago, whileLiujiang 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-dayAsians andNative Americans".[80][81][82][83][84] Tianyuan is similar inmorphology to Liujiang man, and someJōmon period modern humans found in Japan, as well as modern East and Southeast Asians.[85][86][87]
A 2021 study about the population history of Eastern Eurasia, concluded that distinctiveBasal-East Asian (East-Eurasian) ancestry originated inMainland Southeast Asia at ~50,000BC from a distinct southern Himalayan route, and expanded through multiple migration waves southwards and northwards respectively.[88]
According to a 2024 study, Southeast Asia was the "demographic center of expansion" after some Out of African migrantsreturned to Africa, evident by the presence of basal Y-chromosome Eurasian lineages (C, D, F, K) in the region.[89]
Genetic studies concluded thatNative 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 properJōmon 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.[90][91] An indigenous American sample from 16,000BC inIdaho, which is craniometrically similar to modern Native Americans as well asPaleosiberians, was found to have 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.[92]
According toMacaulay et al. (2005), an early offshoot from the southern dispersal with haplogroup N followed the Nile from East Africa, heading northwards and crossing into Asia through theSinai. This group then branched, some moving into Europe and others heading east into Asia.[30] 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.[30] Based on an analysis of 55 human mitochondrial genomes (mtDNAs) of hunter-gatherers,Posth et al. (2016) argue for a "rapid single dispersal of all non-Africans less than 55,000 years ago". By 45,000 years ago, modern humans are known to have reached northwestern Europe.[93]
The first lineage to branch off fromMitochondrial Eve wasL0. This haplogroup is found in high proportions among theSan of Southern Africa and theSandawe of East Africa. It is also found among theMbuti people.[94][95] These groups branched off early in human history and have remained relatively genetically isolated since then.Haplogroups L1,L2, andL3 are descendants of L1–L6, and are largely confined to Africa. The macro haplogroupsM andN, 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.[96][62] The relationship between such gene trees and demographic history is still debated when applied to dispersals.[97]
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, theM andN haplogroup lineages, are found in very low frequencies in Africa (althoughhaplogroup M1 populations are very ancient and diversified inNorth andNorth-east Africa) and appear to be more recent arrivals.[citation needed] A possible explanation is that these mutations occurred in East Africa shortly before the exodus and became the dominant haplogroups thereafter by means of thefounder effect. Alternatively, the mutations may have arisen shortly afterwards.
Results from mtDNA collected from aboriginal Malaysians calledOrang Asli indicate that the haplogroups 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.[30] 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 theHolocene epoch.[98] Alternatively, a small European founder population that had expressed haplogroup M and N at first, could have lost haplogroup M through randomgenetic drift resulting from abottleneck (i.e. afounder effect).
The group that crossed the Red Sea travelled along the coastal route aroundArabia andPersia until reaching India.[57]Haplogroup M is found in high frequencies along the southern coastal regions of Pakistan and India and it has the greatest diversity in India, indicating that it is here where the mutation may have occurred.[57] Sixty percent of the Indian population belong toHaplogroup M. The indigenous people of theAndaman 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 toThailand and Indonesia all the way to easternNew Guinea. Since M is found in high frequencies in highlanders from New Guinea and the Andamanese and New Guineans have dark skin andAfro-textured hair, some scientists think they are all part of the same wave of migrants who departed across the Red Sea ~60,000 years ago in theGreat Coastal Migration. The proportion of haplogroup M increases eastwards fromArabia 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.[citation needed] M is predominant in East Asia, but amongstIndigenous Australians, N is the more common lineage.[citation needed] This haphazard distribution of Haplogroup N from Europe to Australia can be explained byfounder effects andpopulation bottlenecks.[99]
The earliest-branching non-African paternal lineages (C, D, F) after the out-of-Africa event (a), and their deepest divergence among modern day East or Southeast Asia (b), suggesting rapid coastal expansions. SimplifiedY-chromosome tree is shown as reference for colours.[100]
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.[101] A large study by Coopet al. (2009) found evidence fornatural selection inautosomal DNA outside of Africa. The study distinguishes non-African sweeps (notablyKITLG variants associated withskin color), West-Eurasian sweeps (SLC24A5) 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.[102] MC1R and its relation to skin color had already been discussed byHarding et al. (2000), p. 1355. 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.Endicott et al. (2003) suggestconvergent evolution. 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.[103]
Another promising route towards reconstructing human genetic genealogy is via theJC virus (JCV), a type of humanpolyomavirus 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.[104] 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 thisShackelton et al. (2006) 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.
Archaic admixture in some Sub-Saharan African populations hunter-gatherer groups (Biaka Pygmies andSan), derived from archaic hominins that broke away from the modern human lineage around 700,000 years ago, was discovered in 2011. The rate of admixture was estimated at 2%.[34] Admixture from archaic hominins of still earlier divergence times, estimated at 1.2 to 1.3 million years ago, was found inPygmies,Hadza and fiveSandawe in 2012.[107][33]
From an analysis ofMucin 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, it is inferred to have been derived from interbreeding between African modern and archaic humans.[108]
A study published in 2020 found that theYoruba andMende populations of West Africa derive between 2% and 19% of their genome from an as-yet unidentified archaic hominin population that likely diverged before the split of modern humans and the ancestors of Neanderthals and Denisovans.[109]
In addition to genetic analysis, Petragliaet al. also examines the small stone tools (microlithic 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.[110]
The frontispiece to Huxley'sEvidence as to Man's Place in Nature (1863): the image compares the skeleton of a human to other apes.The possibility of an origin ofL3 in Asia was proposed by Cabrera et al. (2018).[111] a: Exit of the L3 precursor to Eurasia.b: Return to Africa and expansion to Asia of basal L3 lineages with subsequent differentiation in both continents.
The cladistic relationship of humans with the Africanapes was suggested byCharles Darwin after studying the behaviour of African apes, one of which was displayed at theLondon Zoo.[112] The anatomistThomas Huxley had also supported the hypothesis and suggested that African apes have a close evolutionary relationship with humans.[113] These views were opposed by the German biologistErnst 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.[114][115]
InThe 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 each great region of the world the living mammals are closely related to the extinct species of the same region. It is, therefore, probable that Africa was formerly inhabited by extinct apes closely allied to thegorilla andchimpanzee; and as these two species are now man's nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere. But it is useless to speculate on this subject, for an ape nearly as large as a man, namely theDryopithecus of Lartet, which was closely allied to the anthropomorphousHylobates, existed in Europe during theUpper Miocene period; and since so remote a period the earth has certainly undergone many great revolutions, and there has been ample time for migration on the largest scale.
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 hypothesis ofrecent (as opposed toarchaic) 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 asCarleton Coon, who thought as late as 1962 thatH. sapiens arose five times fromH. erectus in five places.[117]
The historical alternative to the recent origin model is themultiregional origin of modern humans, initially proposed byMilford Wolpoff in the 1980s. This view proposes that the derivation of anatomically modern human populations fromH. erectus at the beginning of thePleistocene 1.8 million years BP, has taken place within a continuous world population. The hypothesis necessarily rejects the assumption of aninfertility barrier between ancient Eurasian and African populations ofHomo. The hypothesis was controversially debated during the late 1980s and the 1990s.[118] The now-current terminology of "recent-origin" and "Out of Africa" became current in the context of this debate in the 1990s.[119] 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 witharchaic admixture.[120] 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".[121][122]
In the 1980s,Allan Wilson together withRebecca L. Cann andMark Stoneking worked on genetic dating of the matrilineal most recent common ancestor of modern human populations (dubbed "Mitochondrial Eve"). To identify informativegenetic markers for tracking human evolutionary history, Wilson concentrated onmitochondrial DNA (mtDNA), which is maternally inherited. 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 asNeanderthals andHomo erectus had become extinct.[123] With the advent ofarchaeogenetics in the 1990s, the dating of mitochondrial andY-chromosomal haplogroups became possible with some confidence. By 1999, estimates ranged around 150,000 years for themt-MRCA and 60,000 to 70,000 years for the migration out of Africa.[124]
From 2000 to 2003, there was controversy about the mitochondrial DNA of "Mungo Man 3" (LM3) and its possible bearing on themultiregional hypothesis. LM3 was found to have more than the expected number of sequence differences when compared to modern human DNA (CRS).[125] Comparison of the mitochondrial DNA with that of ancient and modernaborigines, 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 of 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.[126]
Map ofY-chromosome haplogroups – dominant haplogroups in pre-colonial populations with proposed migrations routes
TheY chromosome, which is paternally inherited, does not go through much recombination and thus stays largely the same after inheritance. Similar to Mitochondrial Eve, this could be studied to track the male most recent common ancestor ("Y-chromosomal Adam" or Y-MRCA).[127]
The most basal lineages have been detected inWest,Northwest andCentral Africa, suggesting plausibility for the Y-MRCA living in the general region of "Central-Northwest Africa".[13]
AStanford University School of Medicine study was done by comparing Y-chromosome sequences and mtDNA in 69 men from different geographic regions and constructing a family tree. It was found that the Y-MRCA lived between 120,000 and 156,000, and the Mitochondrial Eve lived between 99,000 and 148,000 years ago, which not only predates some proposed waves of migration, but also meant that both lived in theAfrican continent around the same time.[128]
Another study finds a plausible placement in "the north-western quadrant of the African continent" for the emergence of the A1b haplogroup.[129] The 2013 report ofhaplogroup A00 found among theMbo people of western present-dayCameroon is also compatible with this picture.[130]
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 Mendezet al. was tempered by a 2016 study that suggests the extinction of Neanderthal patrilineages, as the lineage inferred from the Neanderthal sequence is outside of the range ofcontemporary human genetic variation.[131] Questions of geographical origin would become part of the debate on Neanderthal evolution fromHomo erectus.
^McChesney (2015): "...genetic evidence suggests that a small band with the marker M168 migrated out of Africa along the coasts of the Arabian Peninsula and India, through Indonesia, and reached Australia very early, between 60,000 and 50,000 years ago. This very early migration into Australia is also supported by Rasmussen et al. (2011)."
^McChesney (2015): "Wells (2003) divided the descendants of men who left Africa into a genealogical tree with 11 lineages. Each genetic marker represents a single-point mutation (SNP) at a specific place in the genome. First, genetic evidence suggests that a small band with the marker M168 migrated out of Africa along the coasts of the Arabian Peninsula and India, through Indonesia, and reached Australia very early, between 60,000 and 50,000 years ago. This very early migration into Australia is also supported by Rasmussen et al. (2011). Second, a group bearing the marker M89 moved out of northeastern Africa into the Middle East 45,000 years ago. From there, the M89 group split into two groups. One group that developed the marker M9 went into Asia about 40,000 years ago. The Asian (M9) group split three ways: into Central Asia (M45), 35,000 years ago; into India (M20), 30,000 years ago; and into China (M122), 10,000 years ago. The Central Asian (M45) group split into two groups: toward Europe (M173), 30,000 years ago and toward Siberia (M242), 20,000 years ago. Finally, the Siberian group (M242) went on to populate North and South America (M3), about 10,000 years ago.[29]
^The researchers used radiocarbon dating techniques on pollen grains trapped in lake-bottom mud to establish vegetation over the ages of theMalawi lake in Africa, taking samples at 300-year-intervals. Samples from the megadrought times had little pollen or charcoal, suggesting sparse vegetation with little to burn. The area aroundLake Malawi, today heavily forested, was a desert approximately 135,000 to 90,000 years ago.[47]
^Liu, Prugnolle et al. (2006). "Currently available genetic and archaeological evidence is supportive of a recent single origin of modern humans in East Africa. However, this is where the consensus on human settlement history ends, and considerable uncertainty clouds any more detailed aspect of human colonization history."
^Scerri, Eleanor M.L.; Drake, Nick A.; Jennings, Richard; Groucutt, Huw S. (2014). "Earliest evidence for the structure of Homo sapiens populations in Africa".Quaternary Science Reviews.101:207–216.Bibcode:2014QSRv..101..207S.doi:10.1016/j.quascirev.2014.07.019.
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^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."
^Genetics and material culture support repeated expansions into Paleolithic Eurasia from a population hub out of Afri, Vallini et al. 2021 (October 15, 2021)Quote: "Taken together with a lower bound of the final settlement of Sahul at 37 kya (the date of the deepest population splits estimated by 1) it is reasonable to describe Papuans as either an almost even mixture between EastAsians and a lineage basal to West and East Asians occurred sometimes between 45 and38kya, or as a sister lineage of East Asians with or without a minor basal OoA or xOoAcontribution."
^Genomic insights into the human population history of Australia and New Guinea, University of Cambridge, Bergström et al. 2018
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