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There's this theory that asserts that all modern humans stem from a single group of Homo sapiens who emerged from Africa 2,000 generations ago, and spread throughout the world over thousands of years. Up until now, one of the main problems with this "Out of Africa" theory was the existence of inconsistent evidence in Australia. The skeletal and tool remains that have been found there are strikingly different from others found along the "coastal expressway" taken by the early settlers. It was a problem until these new findings.
Research has shown that both the Aborigines and the Melanesians from New Guinea, both share the genetic features that have been linked to the exodus of modern humans from Africa 50,000 years ago. This research results show that the "Out of Africa" settlers replaced other early humans in the areas they moved into (Home erectus and Neanderthals) and did not interbreed with them.
Geneticist Dr. Peter Forster, the fellow who led the research has this to say about the new data:
Although it has been speculated that the populations of Australia and New Guinea came from the same ancestors, the fossil record differs so significantly it has been difficult to prove. For the first time, this evidence gives us a genetic link showing that the Australian Aboriginal and New Guinean populations are descended directly from the same specific group of people who emerged from the African migration.
As for the differences in the tools they used, evidence shows that the Australian and Melanesian populations progressed in relative isolation from each other and from the rest of the world after colonization. Dr. Toomas Kivisild of the Cambridge University Department of Biological Anthropology explains:
The evidence points to relative isolation after the initial arrival, which would mean any significant developments in skeletal form and tool use were not influenced by outside sources.
There was probably a minor secondary gene flow into Australia while the land bridge from New Guinea was still open, but once it was submerged the population was apparently isolated for thousands of years. The differences in the archaeological record are probably the result of this, rather than any secondary migration or interbreeding.
It must be noted that Australia's archaeological record shows several inconsistencies with the "Out of Africa" theory. For one thing, some of the earliest skeletons found are slender while younger skeletons are more robust. This suggests interbreeding between Homo sapiens and Homo erectus, or a second migration into Australia, followed by interbreeding. Theories of a second migration has led to many disputes regarding the single point of origin theory.
For now, we guess it's safe to say that whoever you are, you are our cousin, from some ancient mother.
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