In general, the fossil data, the genetic data, and the archaeological data suggest that humans first evolved in Africa more than 2 million years ago and then spread to all other parts of the world. Long before modern humans—Homo sapiens—evolved in Africa about 200,000 years ago, ancient humans began to settle in Europe and Asia. Among the questions facing paleoanthropologists today are when did ancient humans leave Africa and which ancient humans left Africa?
It should be noted that there are a number of human species—Homo neanderthalensis, Homo antecessor, Homo florienses, Homo altai—which evolved outside of Africa, but all of these appear to have evolved from human species that originally evolved in Africa.
Documenting and interpreting the human diaspora are difficult at best. The data comes from several sources, including the fossil record of both ancient and modern human remains, the archaeological record of human artifacts, and, finally, from genetics, which includes both ancient and modern DNA. Overlaying this data is the problem of dating, of determining how hold fossils and artifacts are and how long ago certain events took place. In his chapter in The Oxford Handbook of Archaeology, Steven Mithen writes:
“Revealing the timing and processes by which the world has been colonized by humans is one of the most challenging and important tasks facing archaeology.”
At one time, paleoanthropologists felt that ancient humans did not leave Africa until about a million years ago. However, recent archaeological findings have shown this idea to be incorrect. At Dmanisi, Georgia, archaeologists found stone tools and five skulls which were dated to 1.85 million years ago. The stone tools were similar to the Oldowan tools made by Homo habilis in Africa. The cranial capacities of the skulls ranged from 546 cc to 730 cc, significantly smaller than those of modern humans. In their book From Lucy to Language, Donald Johanson and Blake Edgar write:
“Traditional paleoanthropological thought postulated that hominids did not venture out of Africa until about one million years ago when they were large bodies, big brained bipeds capable of manufacturing tools more sophisticated than Oldowan, and who perhaps even controlled fire to cope with the more seasonal climate. The Dmanisi hominids seriously challenge these assumptions since they were small brained, possessed rudimentary flake and core tools, and, based on fragmentary postcranial remains, were apparently of small stature.”
The Oldowan tool tradition, generally associated with Homo habilis, consists of rather crudely made stone “choppers” and flakes. This is generally considered the oldest stone tool tradition.
It was suggested that the Dmanisi humans be classified as a new species, Homo georgicus, but this proposed designation was withdrawn, and they were tentatively classified as a type of Homo erectus. In his book Humans: From the Beginning, Christopher Seddon writes:
“In modern humans, the elbow joint is typically rotated relative to the shoulder joint, so that the forearm naturally hangs with the palms facing inwards; but the Dmanisi forearm lacked this rotation, so their palms were oriented more forwards. The inward turning feet, lack of humeral torsion, small body size and small brain size may be seen as primitive traits, sharing more in common with Homo habilis than with Homo erectus.”
Archaeological finds in Java also show an early presence of Homo erectus: from 1.65 million years ago to as early as 1.8 million years ago. This suggests that erectus reached Java about the same time Homo ergaster emerged in eastern Africa. Steven Mithen reports:
“These dates suggest that Homo ergaster had not only dispersed from Africa soon after it had evolved, but had also undergone rapid evolutionary change. Indeed, if the earlier date is correct, then the initial dispersal may have been by Homo habilis.”
Regarding the early dates in Java, Richard Klein with Blake Edgar, in their book The Dawn of Human Culture, write:
“In this event, we would either have to abandon the species distinction between ergaster and erectus or we would have to argue that they shared an even older and yet unidentified common ancestor. This ancestor could even have lived in eastern Asia rather than eastern Africa.”
Prior to the re-dating of the Java finds, Leslie Aiello, in The Oxford Companion to Archaeology, had reported:
“Homo ergaster is, at present, the most probable ancestor of the hominids that left Africa and spread into Europe and Asia.”
The Java finds may have changed this hypothesis.
In China, the site at Shangchen in the Loess Plateau suggests a human presence at 2.12 to 1.26 million years ago. Archaeologists working at the site have uncovered 17 artifact layers and have dated the site using paleomagnetic dating. In a report in Current World Archaeology, Lucia Marchini writes:
“No hominin fossils have been found at Shangchen, but archaeologists have analysed 96 stone tools excavated from the site.”
Since stone tools are a human characteristic, this suggests that Shangchen was a site used by ancient humans.
More than 700,000 years ago people in Luzon, Philippines, were butchering rhinos. This suggests that during the Middle Pleistocene (781,000 to 126,000 years ago) people were capable of building watercraft which could reach Luzon from the mainland, crossing the South China sea. These people could have been Homo erectus or Homo altai (Denisovans).
With regard to when ancient humans began migrating from Africa, Steven Mithen writes:
“Although the evidence for hominin dispersal from Africa remains both scanty and difficult to interpret, most paleoanthropologists now agree that this occurred soon after 2 million years ago—more than half-a-million years before the first appearance of handaxes, and while hominins still used an Oldowan-like technology.”
Human Origins
This essay is the first of four essays on leaving Africa. More from this series:
Human Origins: Domesticating Fire
Human Origins: Cannibalism
Human Origins: Menopause
Human Origins: The Great Chain of Being
Human Origins: The Mind
Human Origins: The Large Brain
Human Origins: The Human Hand
Human Origins: Bipedalism
