Early human migrations
Early human migrations are the earliest migrations and expansions of archaic and modern humans across continents. They are believed to have begun approximately 2 million years ago with the early expansions out of Africa by Homo erectus. This initial migration was followed by other archaic humans including H. heidelbergensis, which lived around 500,000 years ago and was the likely ancestor of Denisovans and Neanderthals as well as modern humans. Early hominids had likely crossed land bridges that have now sunk.
Within Africa, Homo sapiens dispersed around the time of its speciation, roughly 300,000 years ago. The recent African origin theory suggests that the anatomically modern humans outside of Africa descend from a population of Homo sapiens migrating from East Africa roughly 70–50,000 years ago and spreading along the southern coast of Asia and to Oceania by about 50,000 years ago. Modern humans spread across Europe about 40,000 years ago.
Early Eurasian Homo sapiens fossils have been found in Misliya Cave, dated to around 194,000–177,000 years old. It has also been claimed by some paleoanthropologists that a skull fragment found in Apidima Cave, dated to around 210,000 years old, may have belonged to Homo sapiens, although that skull fragment can't be confidently attributed to Homo sapiens. These fossils seem to represent failed dispersal attempts by early Homo sapiens, who may have been replaced by local Neanderthal populations.
The migrating modern human populations are known to have interbred with earlier local populations, so that contemporary human populations are descended in small part from regional varieties of archaic humans.
After the Last Glacial Maximum, North Eurasian populations migrated to the Americas about 20,000 years ago. Arctic Canada and Greenland were reached by the Paleo-Eskimo expansion around 4,000 years ago. Finally, Polynesia was populated within the past 2,000 years in the last wave of the Austronesian expansion.
Early humans (before ''Homo sapiens'')
The earliest humans developed out of australopithecine ancestors about 3 million years ago, most likely in the area of the Kenyan Rift Valley, where the oldest known stone tools have been found. Stone tools recently discovered at the Shangchen site in China and dated to 2.12 million years ago are claimed to be the earliest known evidence of hominins outside Africa, surpassing Dmanisi in Georgia by 300,000 years.''Homo erectus''
Between 2 and less than a million years ago, Homo spread throughout East Africa and to Southern Africa, but not yet to West Africa. Around 1.8 million years ago, Homo erectus migrated out of Africa via the Levantine corridor and Horn of Africa to Eurasia. This migration has been proposed as being related to the operation of the Saharan pump, around 1.9 million years ago. Homo erectus dispersed throughout most of the Old World, reaching as far as Southeast Asia. Its distribution is traced by the Oldowan lithic industry, by 1.3 million years ago extending as far north as the 40th parallel.Key sites for this early migration out of Africa are Riwat in Pakistan, Ubeidiya in the Levant and Dmanisi in the Caucasus.
China shows evidence of Homo erectus from 2.12 mya in Gongwangling, in Lantian county. Two Homo erectus incisors have been found near Yuanmou, southern China, and are dated to 1.7 mya, and a cranium from Lantian has been dated to 1.63 mya. Artefacts from Majuangou III and Shangshazui in the Nihewan basin, northern China, have been dated to 1.6–1.7 mya. The archaeological site of Xihoudu in Shanxi province is the earliest recorded use of fire by Homo erectus, which is dated 1.27 million years ago.
Southeast Asia was reached about 1.7 million years ago. Western Europe was first populated around 1.2 million years ago.
Robert G. Bednarik has suggested that Homo erectus may have built rafts and sailed oceans, a theory that has raised some controversy.
After ''Homo erectus''
One million years after its dispersal, H. erectus was diverging into new species. H. erectus is a chronospecies and was never extinct, so its "late survival" is a matter of taxonomic convention. Late forms of H. erectus are thought to have survived until after about 0.5 million ago to 143,000 years ago at the latest, with derived forms classified as H. antecessor in Europe around 800,000 years ago and H. heidelbergensis in Africa around 600,000 years ago. H. heidelbergensis in its turn spread across East Africa and to Eurasia, where it gave rise to Neanderthals and Denisovans.H. heidelbergensis, Neanderthals and Denisovans expanded north beyond the 50th parallel. It has been suggested that late Neanderthals may even have reached the boundary of the Arctic, by c. 32,000 years ago, when they were being displaced from their earlier habitats by H. sapiens, based on 2011 excavations at the site of Byzovaya in the Urals.
Other archaic human species are assumed to have spread throughout Africa by this time, although the fossil record is sparse. Their presence is assumed based on traces of admixture with modern humans found in the genome of African populations. Homo naledi, discovered in South Africa in 2013 and tentatively dated to about 300,000 years ago, may represent fossil evidence of such an archaic human species.
Neanderthals spread across the Near East and Europe, while Denisovans appear to have spread across Central and East Asia and to Southeast Asia and Oceania. There is evidence that Denisovans interbred with Neanderthals in Central Asia where their habitats overlapped. Neanderthal evidence has also been found quite late at 33,000 years ago at the 65th latitude of the Byzovaya site in the Ural Mountains. This is far outside of any otherwise known habitat, during a high ice cover period, and perhaps reflects a refugia of near extinction.
''Homo sapiens''
Dispersal throughout Africa
Homo sapiens are believed to have emerged in Africa about 300,000 years ago, based in part on thermoluminescence dating of artifacts and remains from Jebel Irhoud, Morocco, published in 2017. The Florisbad Skull from Florisbad, South Africa, dated to about 259,000 years ago, has also been classified as early Homo sapiens. Previously, the Omo remains, excavated between 1967 and 1974 in Omo National Park, Ethiopia, and dated to 200,000 years ago, were long held to be the oldest known fossils of Homo sapiens.In September 2019, scientists reported the computerized determination, based on 260 CT scans, of a virtual skull shape of the last common human ancestor to anatomically modern humans, representative of the earliest modern humans, and suggested that modern humans arose between 260,000 and 350,000 years ago through a merging of populations in East and South Africa.
In July 2019, anthropologists reported the discovery of 210,000 year old remains of a H. sapiens and 170,000 year old remains of a H. neanderthalensis in Apidima Cave in southern Greece, more than 150,000 years older than previous H. sapiens finds in Europe.
Early modern humans expanded to Western Eurasia and Central, Western and Southern Africa from the time of their emergence. While early expansions to Eurasia appear not to have persisted, expansions to Southern and Central Africa resulted in the deepest temporal divergence in living human populations. Early modern human expansion in sub-Saharan Africa appears to have contributed to the end of late Acheulean industries at about 130,000 years ago, although very late coexistence of archaic and early modern humans, until as late as 12,000 years ago, has been argued for West Africa in particular.
The ancestors of the modern Khoi-San expanded to Southern Africa before 150,000 years ago, possibly as early as before 260,000 years ago, so that by the beginning of the MIS 5 "megadrought", 130,000 years ago, there were two ancestral population clusters in Africa, bearers of mt-DNA haplogroup L0 in southern Africa, ancestral to the Khoi-San, and bearers of haplogroup L1-6 in central/eastern Africa, ancestral to everyone else. There was a significant back-migration of bearers of L0 towards eastern Africa between 120 and 75 kya.
Expansion to Central Africa by the ancestors of the Central African forager populations most likely took place before 130,000 years ago, and certainly before 60,000 years ago. Wet forest environments were not a major ecological barrier for Homo sapiens as early as around 150,000 years ago.
The situation in West Africa is difficult to interpret due to a scarcity of fossil evidence. Homo sapiens seems to have reached the western Sahelian zone by 130,000 years ago, while tropical West African sites associated with H. sapiens are known only from after 130,000 years ago. Unlike elsewhere in Africa, archaic Middle Stone Age sites appear to persist until very late, down to the Holocene boundary, pointing to the possibility of late survival of archaic humans, and late hybridization with H. sapiens in West Africa.
Early northern Africa dispersal
Populations of Homo sapiens migrated to the Levant and to Europe between 130,000 and 115,000 years ago, and possibly in earlier waves as early as 185,000 years ago.A fragment of a jawbone with eight teeth found at Misliya Cave has 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.
These early migrations do not appear to have led to lasting colonisation and receded by about 80,000 years ago. There is a possibility that this first wave of expansion may have reached China as early as 125,000 years ago, but would have died out without leaving a trace in the genome of contemporary humans.
Image:World map of prehistoric human migrations.jpg|thumb|
Fuller projection map showing early human migrations according to mitochondrial population genetics.
There is some evidence that modern humans left Africa at least 125,000 years ago using two different routes: through the Nile Valley, the Sinai Peninsula and the Levant ; and a second route through the present-day Bab-el-Mandeb Strait on the Red Sea, crossing to the Arabian Peninsula and settling in places like the present-day United Arab Emirates and Oman, and possibly reaching the Indian Subcontinent Although no human remains have yet been found in these three places, the apparent similarities between the stone tools found at Jebel Faya, those from Jwalapuram and some from Africa suggest that their creators were all modern humans. These findings might give some support to the claim that modern humans from Africa arrived at southern China about 100,000 years ago. Dating results of the Lunadong teeth, which include a right upper second molar and a left lower second molar, indicate that the molars may be as old as 126,000 years.
Since these previous exits from Africa did not leave traces in the results of genetic analyses based on the Y chromosome and on MtDNA, it seems that those modern humans did not survive in large numbers and were assimilated by our major antecessors. An explanation for their extinction may be the Toba eruption, though some argue it scarcely affected human population.