KEY POINTS:
The human population in the world today arose from a single migration out of Africa about 55,000 years ago which replaced all other humans who were living in Europe and Asia at the time, a study has found.
Scientists have confirmed the "out of Africa" model of human
origins with a study that combines genetic evidence with physical data gathered from more than 6000 skulls from around the world.
The twin approach has delivered what may turn out to be the killer blow to the rival theory - expounded by Australian anthropologist Alan Thorne, among others - that humans today evolved in several regions of the world, said Andrea Manica of the University of Cambridge, who led the study published in the journal Nature.
"We are fairly convinced of the out of Africa hypothesis because the way we did this study gives us an edge that we didn't have before.
"We looked at the genetics and we looked at the skulls and I really cannot see what other arguments you can come up with to explain what we have observed," he said.
Studies of human DNA and the physical differences between skulls show human variation diminishes the greater the distance from Africa.
This confirms the view that after originating in Africa about 200,000 years ago, anatomically modern Homo sapiens lived on the continent for about 150,000 years before beginning the long trek to Asia, Australia, Europe and finally the Americas.
Other species of humans, such as Homo erectus and Neanderthal man, had already migrated from Africa much earlier in history but they all went extinct after modern humans arrived in their areas.
The latest study appears to confirm - and perhaps prove - that interbreeding between modern Homo sapiens and other human species did not occur, or, if it did, it did not take place on a scale that resulted in any living descendants.
The study also strongly suggests that the cradle of modern humanity lies somewhere in central or southern Africa where Homo sapiens arose and spent about three-quarters of its history before migrating to the four corners of the globe.
Indigenous people living in Australia and South America show the lowest amount of genetic variation as well as differences between the shapes and sizes of their skulls. Meanwhile, the genetic and physical variation between people living in Africa is the greatest anywhere in the world.
Both observations are consistent with the idea that humans migrated out of Africa and analysis of DNA variation suggests this started about 55,000 years ago.
Francois Balloux, a co-author of the study, said that no other explanation for the findings appears forthcoming. "Our findings show that humans originated in a single area of sub-Saharan Africa."
- INDEPENDENT
