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Scientists revamp 'Out of Africa' model of early human migration

Dec. 8 (UPI) — The “Out of Africa” model of early human migration and dispersal is outdated. As a new survey of research on the subject confirms, humans left Africa in waves, not in a single exodus.

In the new survey, published this week in the journal Science, researchers at the Max Planck Institute for the Science of Human History in Germany and the University of Hawai’i at Manoa detail early human evolution revelations reported from Asia over the last decade.

Improved genetic analysis technology, fossil recognition abilities and an emphasis on interdisciplinary research has helped scientists confirm the presence of humans in various parts of Asia much earlier than previously thought.

According to genetic analysis, humans moving into Eurasia interbred with hominins along the way, including Neanderthals and Denisovans.

Taken together, the research on the topic suggests humans migrated out of Africa several times, with the first exodus occurring as early as 120,000 years ago.

Human remains recovered from China have been dated to 70,000 and 120,000 years ago. Fossil dating also suggests humans reached Southeast Asia and Australia prior to 60,000 years ago — the date scientists once thought marked the Out of Africa migration.

The Out of Africa model isn’t all bunk. The latest genetic evidence shows all modern non-African populations branched off from a single African population some 60,000 years ago. The revelation suggests early dispersals were relatively small, isolated and less successful compared to the large migration of human out of Africa that occurred 60,000 years ago.

The later dispersal provided modern populations the majority of their genetic makeup. However, the genetic signatures of earlier human migrations can still be teased out.

“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, researcher with the Max Planck Institute for the Science of Human History, said in a news release. “A later, major ‘Out of Africa’ event most likely occurred around 60,000 years ago or thereafter.”

The latest genetic analysis also proves Neanderthals account for between 1 and 4 percent of the genetic makeup of modern humans. Melanesians, the people of the islands of Oceania, inherit some 5 percent of their genes from the Denisovans.

Just as the spread of human genetics has become an increasingly complicated tale, so has the story of material culture.

“Indeed, what we are seeing in the behavioral record is that the spread of so-called modern human behaviors did not occur in a simple time-transgressive process from west to east,” said Christopher Bae, researcher at the University of Hawai’i at Manoa. “Rather, ecological variation needs to be considered in concert with behavioral variation between the different hominin populations present in Asia during the Late Pleistocene.”

With new revelations continuing to add new wrinkles and complications to the story of early human evolution all the time, the road toward understanding grows longer — but also more interesting.

“It is an exciting time to be involved with interdisciplinary research projects across Asia,” said Bae.

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