SYDNEY (AFP) - - New DNA evidence shows that Australian Aborigines are descended from a wave of migrants who left Africa about 50,000 years ago, researchers at Cambridge University have found.

The researchers said the findings reinforced the "Out of Africa" evolutionary theory, which holds that all modern humans are descended from a single group of "homo sapiens" that left Africa some 2,000 generations ago.

Until now, the main stumbling block for the theory was the huge discrepancy between Aboriginal skeletal and tool remains and those of people elsewhere along the "coastal expressway" -- the route through Asia taken by the early settlers.

Some scholars said the differences showed Australian Aborigines may have interbred with Java man, or "homo erectus", or were descended from a second migratory wave from Africa, according to the Cambridge University website.

But it said analysis of almost 700 DNA samples from Aborigines and the Melanesian people of Papua New Guinea (PNG) showed no evidence of a genetic inheritance from homo erectus.

Cambridge researcher Toomas Kivisild said the study, published this week in the Proceedings of the National Academy of Sciences, indicated Aborigines and Melanesians shared the same ancestor as other modern humans.

He said Australia and Papua New Guinea were joined to the Eurasian land mass by a narrow land bridge at the time of the African migration and its subsequent disappearance meant the populations developed in isolation.

"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," he told the Cambridge University website.

The research was carried by researchers from Cambridge and the nearby Anglia Ruskin University.