Recent African origin of modern humans
In paleoanthropology, the recent African origin of modern humans, frequently dubbed the "Out of Africa" theory, is the most widely accepted model describing the geographic origin and early migration of anatomically modern humans. This model has incorporated the 2010 discovery of genetic evidence for some archaic human admixture with modern Homo sapiens. 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 concept was speculative until the 1980s, when it was corroborated by a study of present-day mitochondrial DNA, combined with evidence based on physical anthropology of archaic specimens.
Genetic studies and fossil evidence show that archaic Homo sapiens evolved to anatomically modern humans solely in Africa, between 200,000 and 60,000 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. The date of the earliest successful "out of Africa" migration (earliest migrants with living descendants) has generally been placed at 60,000 years ago as suggested by genetics, although 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. A 2013 paper reported that a previously unknown lineage had been found, which pushed the estimated date for the most recent common ancestor (Y-MRCA) back to 338,000 years ago.
The recent single origin of modern humans in East 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" 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, which envisions a wave of Homo sapiens migrating earlier from Africa and interbreeding with local Homo erectus 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.
Genetic testing in the last decade has revealed that several now extinct archaic human species may have interbred with modern humans. These species have been claimed to have left their genetic imprint in different regions across the world: Neanderthals in all humans except Sub-Saharan Africans, Denisova hominin in Australasia (for example, Melanesians, Aboriginal Australians and some Negritos) and there could also have been interbreeding between Sub-Saharan Africans and an as-yet-unknown hominin (possibly remnants of the ancient species Homo heidelbergensis). However, the rate of interbreeding was found to be relatively low (1-10%) and other studies have suggested that the presence of Neanderthal or other archaic human genetic markers in modern humans can be attributed to shared ancestral traits originating from a common ancestor 500,000 to 800,000 years ago.
History of the theory
With the development of anthropology in the early 19th century, scholars disagreed vigorously about different theories of human development. Those such as Johann Friedrich Blumenbach and James Cowles Prichard held that since the creation, the various human races had developed as different varieties sharing descent from one people (monogenism). Their opponents, such as Louis Agassiz and Josiah C. Nott, argued for polygenism, or the separate development of human races as separate species or had developed as separate species through transmutation of species from apes, with no common ancestor.
Charles Darwin was one of the first to propose common descent of living organisms, and among the first to suggest that all humans had in common ancestors who lived in Africa. Darwin first suggested the "Out of Africa" hypothesis after studying the behaviour of African apes, one of which was displayed at the London Zoo. The anatomist Thomas Huxley had also supported the hypothesis and suggested that African apes have a close evolutionary relationship with humans. These views were however opposed by Ernst Haeckel the German biologist who was a proponent of the Out of Asia theory. Haeckel argued that humans were more closely related to the primates of Southeast Asia and rejected Darwin’s hypothesis of Africa.
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. Further, 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 the gorilla and chimpanzee; 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 the Dryopithecus of Lartet, which was closely allied to the anthropomorphous Hylobates, existed in Europe during the Upper 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.—Charles Darwin, Descent of Man
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, 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.
In the 1980s Allan Wilson together with Rebecca L. Cann and Mark Stoneking worked on the so-called "Mitochondrial Eve" hypothesis. In his efforts to identify informative genetic markers for tracking human evolutionary history, he started to focus on mitochondrial DNA (mtDNA) – genes that sit in the cell, but not in the nucleus, and are passed from mother to child. This DNA material is important because it mutates quickly, thus making it easy to plot changes over relatively short time spans. By comparing differences in the mtDNA Wilson believed it was possible to estimate the time, and the place, modern humans first evolved. With his discovery that human mtDNA is genetically much less diverse than chimpanzee mtDNA, he concluded that modern human populations had diverged recently from a single population while older human species such as Neandertals and Homo erectus had become extinct. He and his team compared mtDNA in people of different ancestral backgrounds and concluded that all modern humans evolved from one 'lucky mother' in Africa about 150,000 years ago. With the advent of archaeogenetics 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 hypothesis. This work was later questioned and explained by W. James Peacock, leader of the team who sequenced Mungo man's ancient mtdna. In addition, a large-scale genotyping analysis of aboriginal Australians, New Guineans, Southeast Asians and Indians in 2013 showed close genetic relationship between Australian, New Guinean, and the Mamanwa people, with divergence times for these groups estimated at 36,000 y ago. Further, substantial gene flow was detected between the Indian populations and aboriginal Australians, indicating an early "southern route" migration out of Africa, and arrival of other populations in the region by subsequent dispersal. This basically opposes the view that there was an isolated human evolution in Australia.
The question of whether there was inheritance of other typological (not de facto) Homo 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 and the acheulean elaboration of stone tool technologies which occurred between 400,000 years ago and the second interglacial period in the Middle Pleistocene (around 250,000 years ago) provide evidence for a transition from H. erectus 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, found at site Middle Awash in Ethiopia, lived about 160,000 years ago. It is the oldest known anatomically modern human and classified as an extinct subspecies. Fossils of early Homo sapiens were found in Qafzeh cave in Israel 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 et 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 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, 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 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.
Two pieces of the human genome are quite useful in deciphering human history: mitochondrial DNA and the Y chromosome. 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 a woman who lived in Africa about 160,000 years ago. She has been named Mitochondrial Eve. All men living today have inherited their Y chromosomes from a man who lived 140,000–500,000 years ago, probably in Africa. He has been named Y-chromosomal Adam. Based on comparisons of non-sex-specific chromosomes with sex-specific ones, it is now believed that more men than women participated in the out-of-Africa exodus of early humans. [Mendez et al.]
The first lineage to branch off from Mitochondrial Eve is L0. 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 people.
These groups branched off early in human history and have remained relatively genetically isolated since then. Haplogroups L1, L2 and L3 are descendents of L1-6 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 84,000 years old, and haplogroup M and N are almost identical in age at about 63,000 years old. 
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-wide SNP data from the International HapMap Project (Phase II) and CEPH Human Genome Diversity Panel samples was published. Those samples were taken from 1138 unrelated individuals. Before this analysis, population geneticists expected to find dramatic differences among ethnic groups, with derived alleles 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, 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 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. A May 2002 study examined three groups, African, European, and Asian. It 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.
Movement out of Africa
By some 70,000 years ago, a part of the bearers of mitochondrial haplogroup L3 migrated from East Africa into the Near East. The date of this first wave of "out of Africa" migration was called into question in 2011, based on the discovery of stone tools in the United Arab Emirates, indicating the presence of modern humans between 100,000 and 125,000 years ago. New research showing slower than previously thought genetic mutations in human DNA published in 2012, indicating a revised dating for the migration of between 90,000 and 130,000 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 are found outside Africa. From that settlement, some others point to the possibility of several waves of expansion. For example, geneticist Spencer Wells says that the early travellers followed the southern coastline of Asia, crossed about 250 kilometres (155 mi) of sea, and colonized Australia by around 50,000 years ago. The Aborigines of Australia, 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, 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 and N haplogroup lineages, are found in very low frequencies in Africa (although haplogroup M1 is very ancient and diversified in North and Northeast Africa) 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 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 (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 through the Sinai. This group then branched in several directions, some moving into Europe and others heading east into Asia. This hypothesis is supported by relatively late dating of the arrival of modern humans into Europe as well as by both archaeological and DNA evidence. Results from mtDNA collected from aboriginal Malaysians called Orang Asli, and the creation of a phylogentic tree, indicates Hapologroups M and N share characteristics with original African groups dating approximately 85,000 years ago, and sharing characteristics with sub-haplogroups among coastal southeast Asian regions, such as Australasia, the Indian Subcontinent, and throughout continental Asia, which had dispersed and separated from it's African origins approximately 65,000 years ago. This southern coastal dispersion would have occurred before the original theory of dispersion 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 hypothesized to have been destroyed by the rise in sea levels during the Holocene 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 (i.e. a founder effect).
Today at the Bab-el-Mandeb straits the Red 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 was much narrower. Though the straits were never completely closed, they were narrow enough and there may have been islands in between to have enabled crossing using simple rafts. Shell middens 125,000 years old have been found in Eritrea, indicating the diet of early humans included seafood obtained by beachcombing.
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 was reached by Cro-Magnon some 40,000 years ago. East Asia (Korea, Japan) was reached by 30,000 years ago. It is disputed whether subsequent migration to North America 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. 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. 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 mainland Asia. They are evidence of the coastal route of early settlers that extends from India along the coasts of Thailand and Indonesia all the way to Papua New Guinea. 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 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.
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 N reemerges as the more common lineage. This discontinuous distribution of Haplogroup N from Europe to Australia can be explained by founder effects and population bottlenecks.
The multiregional hypothesis, initially proposed by Milford Wolpoff, holds that the evolution of humans from H. erectus at the beginning of the Pleistocene 1.8 million years BP 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 Neanderthals. But the study also suggests that there may be other reasons why humans and Neanderthals share ancient genetic lineages.
- McBride B, Haviland WE, Prins HEL, Walrath D (2012). The Essence of Anthropology. Belmont, CA: Wadsworth Publishing. p. 94. ISBN 978-1-111-83344-2.
- Reid GBR, Hetherington R (2010). The climate connection: climate change and modern human evolution. Cambridge, UK: Cambridge University Press. p. 64. ISBN 0-521-14723-9.
- Meredith M (2011). Born in Africa: The Quest for the Origins of Human Life. New York: PublicAffairs. ISBN 1-58648-663-2.
- Armitage SJ, Jasim SA, Marks AE, Parker AG, Usik VI, Uerpmann HP (January 2011). "The southern route "out of Africa": evidence for an early expansion of modern humans into Arabia". Science 331 (6016): 453–6. Bibcode:2011Sci...331..453A. doi:10.1126/science.1199113. PMID 21273486.
- Mendez, Fernando; Krahn, Thomas; Schrack, Bonnie; Krahn, Astrid-Maria; Veeramah, Krishna; Woerner, August; Fomine, Forka Leypey Mathew; Bradman, Neil; Thomas, Mark; Karafet, Tatiana; Hammer, Michael (2013). "An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree". The American Journal of Human Genetics 92 (3): 454–9. doi:10.1016/j.ajhg.2013.02.002. PMC 3591855. PMID 23453668.
- Liu H, Prugnolle F, Manica A, Balloux F (August 2006). "A geographically explicit genetic model of worldwide human-settlement history". Am. J. Hum. Genet. 79 (2): 230–7. doi:10.1086/505436. PMC 1559480. PMID 16826514. "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."
- "This week in Science: Out of Africa Revisited". Science 308 (5724): 921. 2005-05-13. doi:10.1126/science.308.5724.921g.
- Stringer C (June 2003). "Human evolution: Out of Ethiopia". Nature 423 (6941): 692–3, 695. Bibcode:2003Natur.423..692S. doi:10.1038/423692a. PMID 12802315.
- Johanson D. "Origins of Modern Humans: Multiregional or Out of Africa?". ActionBioscience. American Institute of Biological Sciences.
- "Modern Humans – Single Origin (Out of Africa) vs Multiregional".
- Searching for traces of the Southern Dispersal, by Dr. Marta Mirazón Lahr, et al.
- Balter M (January 2011). "Was North Africa the launch pad for modern human migrations?". Science 331 (6013): 20–3. Bibcode:2011Sci...331...20B. doi:10.1126/science.331.6013.20. PMID 21212332.
- Cruciani F, Trombetta B, Massaia A, Destro-Bisol G, Sellitto D, Scozzari R (June 2011). "A revised root for the human Y chromosomal phylogenetic tree: the origin of patrilineal diversity in Africa". Am. J. Hum. Genet. 88 (6): 814–8. doi:10.1016/j.ajhg.2011.05.002. PMC 3113241. PMID 21601174.
- Smith TM, Tafforeau P, Reid DJ, Grün R, Eggins S, Boutakiout M, Hublin JJ (April 2007). "Earliest evidence of modern human life history in North African early Homo sapiens". Proc. Natl. Acad. Sci. U.S.A. 104 (15): 6128–33. Bibcode:2007PNAS..104.6128S. doi:10.1073/pnas.0700747104. PMC 1828706. PMID 17372199.
- Robert Jurmain; Lynn Kilgore; Wenda Trevathan (20 March 2008). Essentials of Physical Anthropology. Cengage Learning. pp. 266–. ISBN 978-0-495-50939-4. Retrieved 14 June 2011.
- Wolpoff MH, Hawks J, Caspari R (May 2000). "Multiregional, not multiple origins". Am. J. Phys. Anthropol. 112 (1): 129–36. doi:10.1002/(SICI)1096-8644(200005)112:1<129::AID-AJPA11>3.0.CO;2-K. PMID 10766948.
- The Human Stew
- Peter Lafreniere (22 September 2010). Adaptive Origins: Evolution and Human Development. Taylor & Francis. p. 90. ISBN 978-0-8058-6012-2. Retrieved 14 June 2011.
- Robinson D, Ash PM (2010). The Emergence of Humans: An Exploration of the Evolutionary Timeline. New York: Wiley. ISBN 0-470-01315-X.
- Palmer D (2006). Prehistoric Past Revealed: The Four Billion Year History of Life on Earth. Berkeley: University of California Press. p. 43. ISBN 0-520-24827-9.
- Regal B (2004). Human evolution: a guide to the debates. Santa Barbara, Calif: ABC-CLIO. pp. 73–75. ISBN 1-85109-418-0.
- Bowler 2003, p. 213
- "The descent of man Chapter 6 – On the Affinities and Genealogy of Man". Darwin-online.org.uk. Retrieved 2011-01-11.
- Jackson JP Jr (2001). ""In Ways Unacademical": The Reception of Carleton S. Coon's The Origin of Races" (pdf). Journal of the History of Biology 34 (2): 247–285. doi:10.1023/A:1010366015968.
- "Allan Wilson: Revolutionary Evolutionist". New Zealanders Heroes.
- Adcock GJ, Dennis ES, Easteal S, Huttley GA, Jermiin LS, Peacock WJ, Thorne A (January 2001). "Mitochondrial DNA sequences in ancient Australians: Implications for modern human origins". Proc. Natl. Acad. Sci. U.S.A. 98 (2): 537–42. Bibcode:2001PNAS...98..537A. doi:10.1073/pnas.98.2.537. PMC 14622. PMID 11209053.
- Australia Challenges Out-of-Africa Theory ABC News January 9, 2003
- Cooper A, Rambaut A, Macaulay V, Willerslev E, Hansen AJ, Stringer C (June 2001). "Human origins and ancient human DNA". Science 292 (5522): 1655–6. doi:10.1126/science.292.5522.1655. PMID 11388352.
- Smith CI, Chamberlain AT, Riley MS, Stringer C, Collins MJ (September 2003). "The thermal history of human fossils and the likelihood of successful DNA amplification" (PDF). J. Hum. Evol. 45 (3): 203–17. doi:10.1016/S0047-2484(03)00106-4. PMID 14580590.
- Schiller J (2010). Human Evolution: Neanderthals & Homo sapiens. CreateSpace. p. 66. ISBN 978-1-4515-4608-8. Retrieved 29 November 2011.
- Pugach I, Delfin F, Gunnarsdóttir E, Kayser M, Stoneking M (2013). "Genome-wide data substantiate Holocene gene flow from India to Australia". Proc Natl Acad Sci U S A 110 (5): 1803–1808. Bibcode:2013PNAS..110.1803P. doi:10.1073/pnas.1211927110. PMID 23319617.
- Eric Delson; Ian Tattersall; John A. Van Couvering (2000). Encyclopedia of human evolution and prehistory. Taylor & Francis. p. 677–. ISBN 978-0-8153-1696-1. Retrieved 14 June 2011.
- White TD, Asfaw B, DeGusta D, Gilbert H, Richards GD, Suwa G, Howell FC (June 2003). "Pleistocene Homo sapiens from Middle Awash, Ethiopia". Nature 423 (6941): 742–7. Bibcode:2003Natur.423..742W. doi:10.1038/nature01669. PMID 12802332.
- "160,000-year-old fossilized skulls uncovered in Ethiopia are oldest anatomically modern humans". University of California, Berkeley. 2003.
- Clive Finlayson (11 October 2009). The humans who went extinct: why Neanderthals died out and we survived. Oxford University Press US. p. 68. ISBN 978-0-19-923918-4. Retrieved 14 June 2011.
- Liu H, Prugnolle F, Manica A, Balloux F (August 2006). "A geographically explicit genetic model of worldwide human-settlement history". Am. J. Hum. Genet. 79 (2): 230–7. doi:10.1086/505436. PMC 1559480. PMID 16826514.
- Bowler JM, Johnston H, Olley JM, Prescott JR, Roberts RG, Shawcross W, Spooner NA. (2003). "New ages for human occupation and climatic change at Lake Mungo, Australia". Nature 421 (6925): 837–40. Bibcode:2003Natur.421..837B. doi:10.1038/nature01383. PMID 1259451.
- Olleya JM, Roberts RG, Yoshida H and Bowler JM (2006). "Single-grain optical dating of grave-infill associated with human burials at Lake Mungo, Australia". Quaternary Science Reviews 25 (19–20): 2469–2474. Bibcode:2006QSRv...25.2469O. doi:10.1016/j.quascirev.2005.07.022.
- Hu Y, Shang H, Tong H, Nehlich O, Liu W, Zhao C, Yu J, Wang C, Trinkaus E, Richards MP (July 2009). "Stable isotope dietary analysis of the Tianyuan 1 early modern human". Proc. Natl. Acad. Sci. U.S.A. 106 (27): 10971–4. Bibcode:2009PNAS..10610971H. doi:10.1073/pnas.0904826106. PMC 2706269. PMID 19581579.
- Brown P (August 1992). "Recent human evolution in East Asia and Australasia". Philos. Trans. R. Soc. Lond., B, Biol. Sci. 337 (1280): 235–42. doi:10.1098/rstb.1992.0101. PMID 1357698.
- Shen G, Wang W, Wang Q, Zhao J, Collerson K, Zhou C, Tobias PV (December 2002). "U-Series dating of Liujiang hominid site in Guangxi, Southern China". J. Hum. Evol. 43 (6): 817–29. doi:10.1006/jhev.2002.0601. PMID 12473485.
- "Ancestral tools". Handprint.com. 1999-08-01. Retrieved 2011-01-11.
- "Middle to upper paleolithic transition". Wsu.edu. Retrieved 2011-01-11.
- Jones, Marie; John Savino (2007). Supervolcano: The Catastrophic Event That Changed the Course of Human History (Could Yellowstone be Next?). Franklin Lakes, NJ: New Page Books. ISBN 1-56414-953-6.
- Cann RL, Stoneking M, Wilson AC (1987). "Mitochondrial DNA and human evolution". Nature 325 (6099): 31–6. Bibcode:1987Natur.325...31C. doi:10.1038/325031a0. PMID 3025745.
- Vigilant L, Stoneking M, Harpending H, Hawkes K, Wilson AC (September 1991). "African populations and the evolution of human mitochondrial DNA". Science 253 (5027): 1503–7. Bibcode:1991Sci...253.1503V. doi:10.1126/science.1840702. PMID 1840702.
- Keinan A, Mullikin JC, Patterson N, Reich D (January 2009). "Accelerated genetic drift on chromosome X during the human dispersal out of Africa". Nat. Genet. 41 (1): 66–70. doi:10.1038/ng.303. PMC 2612098. PMID 19098910.
- Gonder MK, Mortensen HM, Reed FA, de Sousa A, Tishkoff SA (March 2007). "Whole-mtDNA genome sequence analysis of ancient African lineages". Mol. Biol. Evol. 24 (3): 757–68. doi:10.1093/molbev/msl209. PMID 17194802.
- Chen YS, Olckers A, Schurr TG, Kogelnik AM, Huoponen K, Wallace DC (April 2000). "mtDNA variation in the South African Kung and Khwe-and their genetic relationships to other African populations". Am. J. Hum. Genet. 66 (4): 1362–83. doi:10.1086/302848. PMC 1288201. PMID 10739760.
- Macaulay V, Hill C, Achilli A, Rengo C, Clarke D, Meehan W, Blackburn J, Semino O, Scozzari R, Cruciani F, Taha A, Shaari NK, Raja JM, Ismail P, Zainuddin Z, Goodwin W, Bulbeck D, Bandelt H-J, Oppenheimer S, Torroni A and Richards M 2005. Single, Rapid Coastal Settlement of Asia Revealed by Analysis of Complete Mitochondrial Genomes. Science 308(5724)
- Coop G, Pickrell JK, Novembre J, Kudaravalli S, Li J, Absher D, Myers RM, Cavalli-Sforza LL, Feldman MW, Pritchard JK (June 2009). "The role of geography in human adaptation". In Schierup, Mikkel H. PLoS Genet. 5 (6): e1000500. doi:10.1371/journal.pgen.1000500. PMC 2685456. PMID 19503611.
- Brown, David (June 22, 2009). "Among Many Peoples, Little Genomic Variety". The Washington Post. Retrieved 2009-06-25.
- "Geography And History Shape Genetic Differences In Humans". Science Daily. June 7, 2009. Retrieved 2009-06-25.
- Yu, Ning et al (May 2002). "Larger Genetic Differences Within Africans Than Between Africans and Eurasians". Genetics (Genetics Society of America). Retrieved 7 April 2013.
- "Humans may have left Africa earlier than thought". Apnews.myway.com. Retrieved 2011-06-14.
- Catherine Brahic (24 Nov 2012). "Our True Dawn". New Scientist (Reed Business Information) (2892): 34–7. ISSN 0262-4079.
- "Both Australian Aborigines and Europeans Rooted in Africa". News.softpedia.com. Retrieved 2011-01-11.
- Rincon, Paul (April 24, 2008). "Human line 'nearly split in two'". BBC News. Retrieved 2009-12-31.
- Zhivotovsky, et al; Rosenberg, NA; Feldman, MW (2003). "Features of Evolution and Expansion of Modern Humans, Inferred from Genomewide Microsatellite Markers". American Journal of Human Genetics 72 (5): 1171–86. doi:10.1086/375120. PMC 1180270. PMID 12690579.
- Stix, Gary (2008). "The Migration History of Humans: DNA Study Traces Human Origins Across the Continents". Retrieved 2011-06-14.
- Macaulay V, Hill C, Achilli A, Rengo C, Clarke D, Meehan W, Blackburn J, Semino O, Scozzari R, Cruciani F, Taha A, Shaari NK, Raja JM, Ismail P, Zainuddin Z, Goodwin W, Bulbeck D, Bandelt H-J, Oppenheimer S, Torroni A and Richards M. (2005). Single, Rapid Coastal Settlement of Asia Revealed by Analysis of Complete Mitochondrial Genomes. DOI: 10.1126/science.1109792
- "A single origin, several dispersal hypothesis". Biomedcentral.com. 2004-10-29. Retrieved 2011-01-11.
- Fernandes et. al (June 2006). "Absence of post-Miocene Red Sea land bridges: biogeographic implications". Journal of Biogeography 33 (6): 961–966. doi:10.1111/j.1365-2699.2006.01478.x.
- Beyin, Amanuel (February 2011). "Upper Pleistocene Human Dispersals out of Africa: A Review of the Current State of the Debate". International Journal of Evolutionary Biology 2011 (615094). doi:10.4061/2011/615094.
- Walter RC, Buffler RT, Bruggemann JH, Guillaume MM, Berhe SM, Negassi B, Libsekal Y, Cheng H, Edwards RL, von Cosel R, Néraudeau D, Gagnon M (May 2000). "Early human occupation of the Red Sea coast of Eritrea during the last interglacial". Nature 405 (6782): 65–9. doi:10.1038/35011048. PMID 10811218.
- Literature: Göran Burenhult: Die ersten Menschen, Weltbild Verlag, 2000. ISBN 3-8289-0741-5
- Goebel, Ted; Waters, Michael R.; O'Rourke, Dennis H. (2008). "The Late Pleistocene dispersal of modern humans in the Americas" (PDF). Science 319 (5869): 1497–1502. doi:10.1126/science.1153569. PMID 18339930. Retrieved 2010-02-05.
- Metspalu M, Kivisild T, Metspalu E, Parik J, Hudjashov G, Kaldma K, Serk P, Karmin M, Behar DM, Gilbert MT, Endicott P, Mastana S, Papiha SS, Skorecki K, Torroni A, Villems R (August 2004). "Most of the extant mtDNA boundaries in south and southwest Asia were likely shaped during the initial settlement of Eurasia by anatomically modern humans". BMC Genet. 5: 26. doi:10.1186/1471-2156-5-26. PMC 516768. PMID 15339343.
- "Evolution of Human Languages". Ehl.santafe.edu. Retrieved 2011-01-11.
- Endicott P, Gilbert MT, Stringer C, Lalueza-Fox C, Willerslev E, Hansen AJ, Cooper A (January 2003). "The genetic origins of the Andaman Islanders". Am. J. Hum. Genet. 72 (1): 178–84. doi:10.1086/345487. PMC 378623. PMID 12478481.
- Ingman M, Gyllensten U (July 2003). "Mitochondrial genome variation and evolutionary history of Australian and New Guinean aborigines". Genome Res. 13 (7): 1600–6. doi:10.1101/gr.686603. PMC 403733. PMID 12840039.
- Plagnol V, Wall JD (July 2006). "Possible ancestral structure in human populations". PLoS Genet. 2 (7): e105. doi:10.1371/journal.pgen.0020105. PMC 1523253. PMID 16895447. "..strong evidence for ancient admixture in both a European and a West African population (p ≈ 10−7), with contributions to the modern gene pool of at least 5%. While Neanderthals form an obvious archaic source population candidate in Europe.."
- Green RE, Krause J, Briggs AW, et al. (May 2010). "A draft sequence of the Neandertal genome". Science 328 (5979): 710–22. Bibcode:2010Sci...328..710G. doi:10.1126/science.1188021. PMID 20448178. Lay summary – BBC News.
- Blum MG, Jakobsson M (October 2010). "Deep divergences of human gene trees and models of human origins". Mol. Biol. Evol. 28 (2): 889–98. doi:10.1093/molbev/msq265. PMID 20930054.
- Mellars, Paul (2006). Going East: New Genetic and Archaeological Perspectives on the Modern Human Colonization of Eurasia 313. Science. pp. 769–800.
- Bowler, Peter J. (2003). Evolution: The History of an Idea (3rd ed.). Berkeley: University of California Press. ISBN 0-520-23693-9.
- Darwin, Charles (1871). The Descent of Man, and Selection in Relation to Sex (1st ed.). London: John Murray. Retrieved 2009-09-05.
- Gibbons A (May 2001). "Human anthropology. Modern men trace ancestry to African migrants". Science 292 (5519): 1051–2. doi:10.1126/science.292.5519.1051b. PMID 11352048.
- Underhill PA, Passarino G, Lin AA, Shen P, Mirazón Lahr M, Foley RA, Oefner PJ, Cavalli-Sforza LL (January 2001). "The phylogeography of Y chromosome binary haplotypes and the origins of modern human populations". Ann. Hum. Genet. 65 (Pt 1): 43–62. doi:10.1046/j.1469-1809.2001.6510043.x. PMID 11415522.
- Neanderthals 'mated with modern humans', BBC News, 21 April 1999
- New analysis shows three human migrations out of Africa – Replacement theory 'demolished', Washington University in St. Louis, 2 February 2006
- Harding RM, Healy E, Ray AJ, Ellis NS, Flanagan N, Todd C, Dixon C, Sajantila A, Jackson IJ, Birch-Machin MA, Rees JL (April 2000). "Evidence for variable selective pressures at MC1R". Am. J. Hum. Genet. 66 (4): 1351–61. doi:10.1086/302863. PMC 1288200. PMID 10733465.
- Long JC, Kittles RA (August 2003). "Human genetic diversity and the nonexistence of biological races". Hum. Biol. 75 (4): 449–71. doi:10.1353/hub.2003.0058. PMID 14655871.
- Risch, N., Burchard, E., Ziv, E. and Tang, H. (2002). "Categorization of humans in biomedical research: genes, race and disease". Genome Biology 3 (7): comment2007.2001 – comment2007.2012. doi:10.1186/gb-2002-3-7-comment2007. PMC 139378. PMID 12184798.
- Tishkoff SA, Kidd KK (November 2004). "Implications of biogeography of human populations for 'race' and medicine". Nat. Genet. 36 (11 Suppl): S21–7. doi:10.1038/ng1438. PMID 15507999.
- Cavalli-Sforza F, Cavalli-Sforza LL (1995). The great human diasporas: the history of diversity and evolution. Boston: Addison-Wesley. ISBN 0-201-44231-0.
- Crow TJ, ed. (2004). The Speciation of Modern Homo sapiens (Proceedings of the British Academy). London: British Academy. ISBN 0-19-726311-9.
- Foley R (1995). Humans before humanity: an evolutionary perspective. Oxford: Blackwell. ISBN 0-631-20528-4.
- Olson S (2003). Mapping human history: genes, race, and our common origins. Boston: Houghton Mifflin. ISBN 0-618-35210-4.
- Oppenheimer, Stephen (2003). The Real Eve: Modern Man's Journey Out of Africa. New York, NY: Carroll & Graf. ISBN 0-7867-1192-2.
- McKie R, Stringer C (1997). African exodus: the origins of modern humanity. London: Pimlico. ISBN 0-7126-7307-5.
- Sykes, Bryan (2004). The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry. Corgi Adult. ISBN 0-552-15218-8.
- Wade N (2006). Before the Dawn : Recovering the Lost History of Our Ancestors. Penguin Press HC, The. ISBN 1-59420-079-3.
- Wells S (2004). Journey of Man: Genetic Odyssey. Random House. ISBN 0-8129-7146-9.
- Wells, Spencer (2006). Deep ancestry: inside the Genographic Project. Washington, D.C: National Geographic. ISBN 0-7922-6215-8.
- Manica A, Amos W, Balloux F, Hanihara T (July 2007). "The effect of ancient population bottlenecks on human phenotypic variation". Nature 448 (7151): 346–8. Bibcode:2007Natur.448..346M. doi:10.1038/nature05951. PMC 1978547. PMID 17637668. Lay summary – Science Daily.
- Scholz CA, Johnson TC, Cohen AS, King JW, Peck JA, Overpeck JT, Talbot MR, Brown ET, Kalindekafe L, Amoako PY, Lyons RP, Shanahan TM, Castañeda IS, Heil CW, Forman SL, McHargue LR, Beuning KR, Gomez J, Pierson J (October 2007). "East African megadroughts between 135 and 75 thousand years ago and bearing on early-modern human origins". Proc. Natl. Acad. Sci. U.S.A. 104 (42): 16416–21. Bibcode:2007PNAS..10416416S. doi:10.1073/pnas.0703874104. PMC 1964544. PMID 17785420. Lay summary – Science Daily.
- Cohen AS, Stone JR, Beuning KR, Park LE, Reinthal PN, Dettman D, Scholz CA, Johnson TC, King JW, Talbot MR, Brown ET, Ivory SJ (October 2007). "Ecological consequences of early Late Pleistocene megadroughts in tropical Africa". Proc. Natl. Acad. Sci. U.S.A. 104 (42): 16422–7. Bibcode:2007PNAS..10416422C. doi:10.1073/pnas.0703873104. PMC 2034256. PMID 17925446. Lay summary – Science Daily.
- Smith L (2007-10-09). "Climate change led mankind out of Africa". Times Online.
- Russell S (2008-02-22). "DNA studies trace human migration from Africa". San Francisco Chronicle.
- Serre D, Langaney A, Chech M, Teschler-Nicola M, Paunovic M, Mennecier P, Hofreiter M, Possnert G, Pääbo S (March 2004). "No evidence of Neandertal mtDNA contribution to early modern humans". PLoS Biol. 2 (3): E57. doi:10.1371/journal.pbio.0020057. PMC 368159. PMID 15024415.
- Stringer, Chris (2011). The Origin of Our Species. London: Allen Lane. ISBN 978-1-84614-140-9.
- The Human Family Tree – by Spencer Wells – National Geographic
- An mtDNA view of the peopling of the world by Homo sapiens (archived version)
- National Geographic: Atlas of the Human Journey
- Bradshaw Foundation: The Journey of Mankind
- Human Evolution. (2011). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/275670/human-evolution
- 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 – Discovery Channel, 2002
- Journey of Man: A Genetic Odyssey (movie) by Spencer Wells – PBS and National Geographic Channel, 2003