The "Out of Africa" theory of human evolution has been under a lot of pressure lately. And while the "Out of Europe" theory that floated around briefly has been put to bed, it turns out that the old model does need a little revising. Specifically, the assumption that there was one tribe of travel-curious Homo sapiens who left Africa in a great migration some 60,000 years ago and from which all modern humans of non-African ancestry descend from. New research suggests that the first prehistoric human to leave Africa did so as early as 120,000 years ago.
An international team of researchers from the Max Planck Institute for the Science of Human History in Jena, Germany, and the University of Hawaii at Manoa, United States, reviewed several recent studies that seem to be at odds with the old "Out of Africa" theory. Their findings have been published in the journal Science.
The researchers analyzed discoveries in Asia and Near Oceania, which push back the first migrations out of Africa by 60,000 years. These include human remains archaeologists found in central and southern China that are between 70,000 and 120,000 years old, and others in Southeast Asia and Australia that are more than 60,000 years old.
But things are made more complicated by a number of other studies that seem to confirm that people of non-African ancestry did indeed descend from a single population that migrated some 60,000 years ago.
Out of Africa 2.0 does not entirely discard the old theory, but the new model instead proposes that there were smaller groups of pioneers who left Africa prior to a much larger migration, and it is from this second group that the majority of non-Africans' genetic makeup comes from.
"The initial dispersals out of Africa prior to 60,000 years ago were likely by small groups of foragers, and at least some of these early dispersals left low-level genetic traces in modern human populations," Michael Petraglia of the Max Planck Institute for the Science of Human History explained in a statement. "A later, major 'Out of Africa' event most likely occurred around 60,000 years ago or thereafter."
But that's not all. On their adventures, these early explorers met and interbred with various hominin relatives, including the Neanderthals and Denisovans. Some estimates suggest that 1-2 percent of DNA in present-day non-Africans is Neanderthal and up to 5 percent of DNA in modern Melanesians is Denisovan.
What this review shows is that uncovering our evolutionary story is an ongoing process and new evidence still has the potential to shake up what we think we know. As the researchers point out, there is more work to be done, particularly in areas of Asia that have been overlooked.
"It is an exciting time to be involved with interdisciplinary research projects across Asia," said Christopher Bae of the University of Hawai'i at Manoa.