DNA Evidence Sheds Light on When Humans First Left Africa

MASSEY UNIVERSITY 
 
   Work by Massey University professor Murray Cox contributed to the findings

MASSEY UNIVERSITY Work by Massey University professor Murray Cox contributed to the findings

We know that tens of thousands of years ago, humans migrated out of Africa - but the question is, when, and how many times?

Aboriginal Australians have always been known as one of the oldest surviving distinct populations of our species.

These questions about human evolution have remained unanswered for decades, but a new study suggests that there may now be an explanation.

All non-Africans alive today descended from a single migration out of Africa almost 72,000 years ago, a new research has shown.

"I think all three studies are basically saying the same thing", Joshua M. Akey from the University of Washington, who co-wrote a commentary accompanying the findings, said.

It's always been understood that modern humans can trace their origin to Africa, from where we eventually made our way northward and out to other corners of the world.

The three teams sequenced the genomes of 787 people, obtaining highly detailed scans of each. The genomes were drawn from people in hundreds of indigenous populations: Basques, African pygmies, Mayans, Bedouins, Sherpas and Cree Indians, to name just a few.

The aboriginal genomes were compared with genetic information about other populations, which gave them confidence a single mass migration out of Africa was what likely happened. Was there just one population of early humans in Africa at the time?

Thanks to a series of genome sequences, three separate groups of scientists conclude that all modern non-Africans trace their ancestry to a single population that emerged from Africa about 50,000 to 80,000 years ago.

Hints of an early exodus of modern humans from Africa may have been detected in living humans.

Early studies of bits of DNA also supported this idea.

Not only did they uncover population X, but found that modern Papuans carry its legacy in tiny amounts of their DNA.

DNA Evidence Sheds Light on When Humans First Left Africa
DNA Evidence Sheds Light on When Humans First Left Africa

BEACON TRANSCRIPT- Where does the modern human come from? Several tools were found in India that were 100,000 years old.

Intriguingly, their data showed little evidence of genetic shifts during the periods when modern humans are known to have picked up modern habits like art and burial rituals.

A similar conclusion is made by Eske Willerslev, a researcher from the University of Copenhagen, Danemark and his colleagues.

Dr. Willerslev and his colleagues reconstructed the genome from a century-old lock of hair kept in a museum. But by conducting studies like these, where the latest genetic techniques are applied to understudied populations, researchers may soon be able to paint a complete picture of humanity's global dispersal. He joined David W. Lambert, a geneticist at Griffith University in Australia, who was already meeting with aboriginal communities about beginning such a study.

Meanwhile, Mait Metspalu of the Estonian Biocentre was leading a team of 98 scientists on another genome-gathering project. But their study finds a more gradual split into the groups that went on to populate west and east Eurasia.

These affirmations can be seen in The Simons Genome Diversity Project Study, which was the one that proved all of the human's genes can be traced back to the massive expansion from the continent.

David Reich, a geneticist at Harvard Medical School, and his colleagues assembled a third database of genomes from all five continents. These populations have been thought in the past to derive from much earlier migrations, but the study found otherwise. The estimates from the studies point to an exodus somewhere between 80,000 and 50,000 years.

But in natives from Papua New Guinea, the researchers found that 2.0 percent of their genomes show DNA evidence of an earlier migration of home sapiens out of Africa.

"The vast majority of their ancestry - if not all of it - is coming from the same out-of-Africa wave as Europeans and Asians", Willerslev said.
The Danish study, the most comprehensive analysis of Aboriginal Australian and Papuan genomes to date, is the first to really examine the position of Australia at the end of the migration.

"This suggests most Eurasians diverged from Africans in a single event... about 75,000 years ago, while the Papuan split was more ancient - about 90,000 years ago". But the other 2 percent seemed to be much older.

Australia and New Guinea have some of the earliest archaeological and fossil evidence of modern humans outside of Africa, and it had been speculated that Aboriginals may have originated from an earlier, Asia-bound, exit from Africa.

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