Convoluted human evolution: Africa started it (Introduction)

by David Turell , Wednesday, September 21, 2016, 20:22 (2766 days ago) @ David Turell

New DNA evidence says all of us started in Africa:-https://www.newscientist.com/article/2106791-the-most-detailed-look-yet-at-how-early-humans-left-africa/-"All non-Africans living today can trace the vast majority of their ancestry to a group of pioneers who left Africa in a single wave, tens of thousands of years ago.
We still don't know the exact timing of that migration, precisely where it began, nor the details of movements and how individual populations developed within Africa.
But the discovery of a single exit is a major advance in illuminating the earliest days of humanity's global sprawl, says Joshua Akey at the University of Washington in Seattle.-"Developing a fuller picture of our ancestry requires the study of a range of diverse human populations. Collectively, the authors of three new studies took on that challenge by analysing the genomes of 787 people from more than 270 populations scattered across the globe.-"Genetic similarities between populations show clear evidence for a single exit from Africa, says David Reich at Harvard University. Reich and his colleagues also determined that our African ancestors had already begun diverging into separate groups 200,000 years ago.-"The researchers also looked for a mutation that might have occurred between 50,000 and 80,000 years ago, when human technology and culture took off, with advances in art, burial rituals and tool use.-"But the team failed to find a genetic smoking gun, suggesting that progress was instead propelled by an environmental or lifestyle change, Reich says.-***-"Environmental conditions, such as temperature and plant growth, may have prompted some early human migrations (see box below). And geographical barriers such as mountains and deserts may have kept populations separate, perpetuating genetic differences around the world, according to another of the genetics studies, led by Luca Pagani and Mait Metspalu at the Estonian Biocentre in Tartu.-"Pagani and Metspalu and their colleagues also concluded that most modern non-Africans are descended from a single, out-of-Africa migration. But about 2 per cent of the genome of people from Papua New Guinea comes from an earlier exodus, Pagani says.-“'We see vestiges of an earlier out-of-Africa expansion,” Metspalu says. But, in the end, the main migration almost completely overwhelmed that small, early wave, he adds.
In the first comprehensive study of genetic diversity among Indigenous Australians, Eske Willerslev at the University of Copenhagen in Denmark and his colleagues found that different indigenous groups within Australia are genetically quite distinct, but that they are all descended from a single, founding wave of people from Africa.-"Because Indigenous Australians are prone to diabetes, studying their DNA could explain the genetic drivers behind the disease, Willerslev says.
“They could potentially hold the key as to why other non-Africans also have diabetes,” he says.-"That kind of medical insight is one reason to delve into humanity's genetic history, says Akey.-"Another is simple curiosity about where we came from. But solving that riddle will require contributions from fields outside genetics, too, Akey says, such as archaeology and ecology.:-Comment: I recently published a story about the Chinese studying human fossil DNA looking for a Chinese contribution to hum an development. We seem to have an urge to travel like the Pacific Islanders