Early human migrations

• 1. Introduction

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  Fewer than 1,000 individuals may have crossed the Bab-el-Mandeb strait after around 75,000 years ago, carrying mitochondrial haplogroup L3 from East Africa into what is now Yemen. From that small band descend the human populations of nearly every continent. Early human migrations are the spread of archaic and modern humans across the Earth, and they reach back roughly 2 million years. How did a single African genus become a planet-wide species? Why did some early journeys leave no genetic trace at all, dying out while others endured? What did people need to invent to survive Arctic cold, cross open ocean, or follow herds across glacial steppe? The answers move through sunken land bridges and volcanic catastrophe, through interbreeding with vanished cousins, and through the final boats that found the most remote islands on Earth.

• 2. The First Walkers

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  About 3 million years ago, the earliest humans developed out of australopithecine ancestors, most likely in the Kenyan Rift Valley, where the oldest known stone tools have been found. The Rift was the workshop of human beginnings, the place where toolmaking and the genus Homo first took shape.

  Stone tools at the Shangchen site in China, dated to 2.12 million years ago, are claimed as the earliest known evidence of hominins outside Africa. That date surpasses Dmanisi in Georgia by 300,000 years, pushing the human story beyond Africa far earlier than once thought. Early hominids had likely crossed land bridges that have now sunk beneath rising seas, leaving their routes invisible.

  Between 2 and less than a million years ago, Homo spread throughout East Africa and to Southern Africa as Homo ergaster, but had not yet reached West Africa. The map of early human presence was patchy and uneven, shaped by terrain and climate rather than any single sweeping advance. The next chapter belongs to the species that turned this regional spread into an intercontinental one.

• 3. Homo Erectus Goes Global

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  Around 1.8 million years ago, Homo erectus migrated out of Africa via the Levantine corridor and the Horn of Africa into Eurasia. This movement has been linked to the Saharan pump operating around 1.9 million years ago, the climatic mechanism that periodically turned the desert green and opened a path north.

  Dmanisi in the Caucasus, dated to 1.81 million years ago, sits among the key sites of this exodus, alongside Riwat in Pakistan and Ubeidiya in the Levant at 1.5 million years ago. The trail of the Oldowan stone-tool industry traces the spread, reaching as far north as the 40th parallel at Xiaochangliang by 1.3 million years ago. China holds an especially deep record, with Homo erectus at Gongwangling in Lantian county from 2.12 million years ago and two incisors near Yuanmou dated to 1.7 million years ago.

  The site of Xihoudu in Shanxi province preserves the earliest recorded use of fire by Homo erectus, dated to 1.27 million years ago. Fire meant warmth, cooked food, and the ability to push into colder and darker places. Java was reached about 1.7 million years ago by the form known as Meganthropus, and Western Europe was first populated around 1.2 million years ago at Atapuerca.

  Robert G. Bednarik has suggested that Homo erectus may have built rafts and sailed oceans, a theory that has raised some controversy. Whether or not they sailed, these early people had crossed the Lombok gap and reached the island of Flores, a feat that points the next chapter toward the species that erectus became.

• 4. Cousins In The Cold

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  One million years after its dispersal, Homo erectus was diverging into new species, giving rise to Homo antecessor in Europe around 800,000 years ago and Homo heidelbergensis in Africa around 600,000 years ago. Heidelbergensis spread across East Africa as Homo rhodesiensis and into Eurasia, where it gave rise to Neanderthals and Denisovans.

  These populations pushed north beyond the 50th parallel, marked by sites such as Boxgrove in England at 500,000 years ago and Denisova Cave at 50,000 years ago. Cold was no longer a hard frontier. Late Neanderthals may even have reached the boundary of the Arctic by about 32,000 years ago, based on 2011 excavations at Byzovaya in the Urals, in the Komi Republic.

  Byzovaya, at the 65th latitude, yielded Neanderthal evidence as late as 33,000 years ago, far outside any otherwise known habitat and during a period of high ice cover. Researchers suggest it may reflect a refuge of near extinction, a last stand as Homo sapiens displaced Neanderthals from their earlier homes.

  Denisovans appear to have spread across Central and East Asia and on to Southeast Asia and Oceania, while Neanderthals held the Near East and Europe. There is evidence the two interbred in Central Asia where their ranges overlapped. In South Africa, Homo naledi, discovered in 2013 and tentatively dated to about 300,000 years ago, may represent yet another archaic line whose presence is otherwise known only from faint genetic traces in living Africans.

• 5. Born In Africa

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  Thermoluminescence dating of artifacts and remains from Jebel Irhoud, Morocco, published in 2017, places the emergence of Homo sapiens in Africa about 300,000 years ago. The Florisbad Skull from South Africa, dated to about 259,000 years ago, has also been classified as early Homo sapiens, while the Omo remains from Ethiopia, excavated between 1967 and 1974 and dated to 200,000 years ago, were long held to be the oldest.

  In September 2019, scientists reported a virtual skull shape of the last common ancestor of anatomically modern humans, based on 260 CT scans. They suggested modern humans arose between 260,000 and 350,000 years ago through a merging of populations in East and South Africa. The origin was not a single point but a web of mixing groups across a continent.

  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. By the MIS 5 megadrought 130,000 years ago, two ancestral clusters existed: bearers of mt-DNA haplogroup L0 in southern Africa, ancestral to the Khoi-San, and bearers of L1-6 in central and eastern Africa, ancestral to everyone else. A significant back-migration of L0 toward eastern Africa followed between 120,000 and 75,000 years ago.

  Expansion into Central Africa by the ancestors of forager populations most likely took place before 130,000 years ago, and wet forest was no major barrier as early as around 150,000 years ago. West Africa remains hard to read because fossils are scarce. There, archaic Middle Stone Age sites appear to persist down to the Holocene boundary 12,000 years ago, hinting at late survival of archaic humans and late hybridization with Homo sapiens.

• 6. The Failed Exits

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  A fragment of jawbone with eight teeth from Misliya Cave in Israel has been dated to around 185,000 years ago, evidence that Homo sapiens reached the Levant far earlier than once believed. Layers in the same cave dating between 250,000 and 140,000 years ago held tools of the Levallois type, which could push the first migration earlier still if those tools belong to the modern human finds.

  Qafzeh Cave in the Levant, dated to between 120,000 and 100,000 years ago, marks one of two early routes out of Africa, the other crossing the Bab-el-Mandeb strait on the Red Sea. Along that southern path, sites appear at Jebel Faya in the present-day United Arab Emirates around 125,000 years ago and in Oman around 106,000 years ago. The similarity of stone tools at Jebel Faya, at Jwalapuram in India dated to 75,000 years ago, and in Africa suggests their makers were all modern humans.

  Zhiren Cave in Chongzuo City, southern China, dated to 100,000 years ago, supports the claim that modern humans reached the region early, alongside the Liujiang hominid controversially dated at 139,000 to 111,000 years old. Two teeth from Lunadong in Guangxi may be as old as 126,000 years. Yet none of these journeys left a mark in the Y-chromosome or mtDNA of living people.

  These early migrations receded by about 80,000 years ago, the travelers assimilated by later arrivals or simply gone. One proposed cause of their disappearance is the Toba eruption 74,000 years ago, though some argue it scarcely affected human numbers. A skull fragment from Apidima Cave in Greece, dated to around 210,000 years ago, may belong to Homo sapiens, though it cannot be confidently attributed. Such fossils seem to record failed attempts, early pioneers replaced by local Neanderthals before the journey that finally stuck.

• 7. The Coast And The Sea

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  The recent dispersal that finally peopled the world took place about 70,000 to 50,000 years ago, carrying mitochondrial haplogroups M and N, both derived from L3. The descendants of that crossing spread along the coastal route around Arabia and Persia to South Asia before 55,000 years ago. A northern route through the Sinai Peninsula and the Levant also has support.

  Australia was colonized by around 65,000 to 50,000 years ago, and by reaching it Homo sapiens expanded its habitat beyond anything Homo erectus had managed. Erectus had reached Flores but never crossed to Australia. Along the way modern humans interbred with Neanderthals and Denisovans, with Denisovan DNA making up 0.2% of mainland Asian and Native American DNA.

  Maritime Southeast Asia then formed one land mass called Sunda, separated from the Sahul continent of Australia and New Guinea by the gaps of the Weber Line, up to 90 km wide. Crossing them required seafaring skills. Denisovan ancestry is shared by Melanesians, Aboriginal Australians, and groups such as the Mamanwa, a Negrito people in the Philippines, and Denisovans may have crossed the Wallace Line, with Wallacea as their last refuge.

  Sequencing of one Aboriginal genome from an old hair sample in Western Australia showed descent from people who migrated into East Asia between 62,000 and 75,000 years ago. Australia and New Guinea were separated by rising seas roughly 8,000 years ago. Tim Flannery has argued that humans drove the extinction of the Australian megafauna between 46,000 and 15,000 years ago, a pattern echoed later on another continent.

• 8. Filling The Last Frontiers

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  Presence in Europe is certain after 40,000 years ago, possibly as early as 43,000 years ago, as modern humans rapidly replaced the Neanderthals. The Cro-Magnons entered Eurasia by the Zagros Mountains around 50,000 years ago, one group settling the Indian Ocean coast and another moving north to the Central Asian steppes. They survived the cold through tailored clothing of fur pelts, shelters with hearths burning bone, and ice cellars dug into the permafrost to store meat.

  The eruption of the super-volcano in the Phlegrean Fields near Naples in about 38,000 BCE left much of eastern Europe under ash and, by recent research, wiped out both the last Neanderthals and the first Upper Paleolithic Homo sapiens. Modern Europeans carry no trace of those first European sapiens, only of populations that repopulated the continent from the east after the eruption. Neanderthals disappeared about 40,000 years ago, their last refuge in the Iberian Peninsula.

  Tianyuan man, who lived in China about 40,000 years ago, carried substantial Neanderthal admixture and is related to modern Asian and Native American populations. A distinctive Basal-East Asian lineage, ancestral to East Asians, Southeast Asians, Polynesians, and Siberians, is thought to have originated in Mainland Southeast Asia around 50,000 BC. A Paleolithic site on the Yana River in Siberia, at 71 degrees north and well above the Arctic Circle, dates to 27,000 radiocarbon years before present.

  Around 20,000 years ago, after the Last Glacial Maximum, North Eurasian populations crossed the Beringia land bridge between eastern Siberia and Alaska into the Americas. Conventional estimates place humans in North America between 15,000 and 20,000 years ago, following ice-free corridors between the Laurentide and Cordilleran ice sheets or moving down the Pacific coast as far as Chile. The discovery of Australasian genetic markers in Amazonia supports a coastal route followed by isolation.

  The Holocene, beginning 12,000 years ago, brought the last great waves. Austronesian peoples from Taiwan built the first sea-going ships, using catamarans, outrigger boats, and crab claw sails to colonize Island Southeast Asia around 3000 to 1500 BCE. Their Lapita-culture descendants reached Samoa and Tonga by around 900 to 800 BCE, then Hawaii by 900 CE, Rapa Nui by 1000 CE, and New Zealand by 1200 CE. The Inuit, descendants of the Thule culture that emerged from western Alaska around 1000 CE, were among the very last, gradually displacing the Dorset culture across the Arctic that humans had taken some 2 million years to reach in full.