New human DNA research adds to “Out of Africa” theories

   It would seem that human DNA research has provided a new wrinkle, a new twist to existing theories about how non-Africans originated, and the diaspora  from Africa that took place several thousands of years ago. And it’s all based on three separate studies that came up with similar, yet ultimately varying findings that agreed on one area — Eurasians and indigenous Papua New Guineans may have descended from one single migration from Africa.

Homo sapiens had first emerged approximately 200,000 years ago in Africa, and would eventually become the predominant human species as they departed from the continent, and the ancestor of today’s humans. But researchers have long been left scratching their heads on when exactly the exodus from Africa took place.

With the new studies, the researchers are making use of the fact that human DNA is like a scrapbook in the process of getting updated, as new changes are manifested over a period of time. These updates can be used to determine the timeline of certain diasporas from Africa. And while earlier studies had suggested that the migration took place among a single population about 40,000 to 80,000 years ago, with subsequent migrations taking place over time, one of the newer ones suggests that migration may have happened as far back as 120,000 to 130,000 years ago.


More interestingly, one of the studies suggests that there may have been an earlier migration in native Papua New Guineans. The study notes that at least 2 percent of these aboriginal Papua New Guineans’ DNA may have originated from a population that broke off from early Africans about 120,000 years ago.

“All three papers all reach the same conclusions: that in Eurasians and also (Papua New Guineans), the majority of their genomes come from the same major migration,” said University of Cambridge biologist Luca Pagani, speaking to BBC about the similarities in all the three studies.

Working with his fellow researchers from the Estonian Biocentre, Pagani and colleagues studied 483 human genomes from 148 populations. They were able glean that large groups of people had departed from Africa at separate times, and that most Eurasians had made the move more recently than aboriginal Australians and Papua New Guineans.

“All the other Eurasians we had were very homogenous in their split times from Africans,” Pagani continued. “This suggests most Eurasians diverged from Africans in a single event … about 75,000 years ago, while the (Papua New Guinea) split was more ancient – about 90,000 years ago. So we thought there must be something going on.”

The other studies had come to the conclusion that any genetic features from earlier migrations may be very limited. One of the papers, from the Harvard Medical School, looked at 300 people from 142 populations, while another, from the Centre for GeoGenetics, had studied the genetic features of 111 aboriginal people – 25 from Papua and 83 from Australia. The Centre for GeoGenetics paper noted, quite interestingly, that there may be proof of a single migration taking place from Africa about 51,000 to 72,000 years ago. The Harvard study, on the other hand, posited that there may have been a single migration 100,000 years ago, but the people in that migration were not the forebears of any modern human populations.

While the two aforementioned studies have different findings than Pagani’s study, it does appear as if the majority of the ancestry of modern humans came from one single diaspora.

“Indigenous Australians, New Guineans, and Andamanese do not derive substantial ancestry from an early dispersal of modern humans; instead, their modern human ancestry is consistent with coming from the same source as that of other non-Africans,” said the authors of the Harvard human DNA study.