Almost All Living People Outside Of Africa Trace Back To A Single Migration More Than 50,000 Years Ago
Posted by addisethiopia on September 22, 2016
Australian Aborigines have long been cast as a people apart. Although Australia is halfway around the world from our species’s accepted birthplace in Africa, the continent is nevertheless home to some of the earliest undisputed signs of modern humans outside Africa, and Aborigines have unique languages and cultural adaptations. Some researchers have posited that the ancestors of the Aborigines were the first modern humans to surge out of Africa, spreading swiftly eastward along the coasts of southern Asia thousands of years before a second wave of migrants populated Eurasia.
Not so, according to a trio of genomic studies, the first to analyze many full genomes from Australia and New Guinea. They conclude that, like most other living Eurasians, Aborigines descend from a single group of modern humans who swept out of Africa 50,000 to 60,000 years ago and then spread in different directions. The papers “are really important,” says population geneticist Joshua Akey of the University of Washington, Seattle, offering powerful testimony that “the vast majority of non-Africans [alive today] trace their ancestry back to a single out-of-Africa event.”
Yet the case isn’t closed. One study argues that an earlier wave of modern humans contributed traces to the genomes of living people from Papua New Guinea. And perhaps both sides are right, says archaeologist Michael Petraglia of the Max Planck Institute for the Science of Human History in Jena, Germany, a co-author on that paper who has long argued for an early expansion out of Africa. “We’re converging on a model where later dispersals swamped the earlier ones,” he says.
A decade ago, some researchers proposed the controversial idea that an early wave of modern humans left Africa more than 60,000 years ago via a so-called coastal or southern route. These people would have launched their migration from Ethiopia, crossing the Red Sea at its narrowest point to the Arabian Peninsula, then rapidly pushing east along the south Asian coastline all the way to Australia. Some genetic studies, many on mitochondrial DNA of living people, supported this picture by indicating a relatively early split between Aborigines and other non-Africans. But analysis of whole genomes— the gold standard for population studies— was scanty for many key parts of the world.