May 8, 2007
The theory that all modern humans descended out of Africa is almost certainly correct, new research claims.
According to the 'Out of Africa' theory, all modern humans come from a single group of Homo sapiens who emigrated from Africa 2,000 generations ago and spread throughout Europe and Asia over thousands of years.
They then replaced other early human settlers, such as Neanderthals, rather than interbreeding with them.
Some scientists have said that there is evidence which dispels this theory, but a new study claims that its DNA evidence proves Out of Africa to be true.
A team led by scientists at Cambridge and Anglia Ruskin Universities found that Australia's Aboriginal population comes from the same small group of colonists as their neighbours in New Guinea.
They came to this conclusion after analysing the mitochondrial DNA and Y chromosomes of Aboriginal Australians and Melanesians from New Guinea.
The results showed that they share the same genetic features that have been associated with the exodus from Africa 50,000 years ago.
Early humans were able to travel to Australia via a land bridge that was submerged by water 8,000 years ago. This, the study's authors claim, explains why the fossil and archaeological record in Australia is so different to that found elsewhere even though genetic evidence shows no interbreeding with Homo erectus.
Dr Toomas Kivisild, the report's co-author from Cambridge University, explained: "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."
The findings are published in the Proceedings of the National Academy of Sciences journal.