The prevailing theory among scientists is the "out of Africa theory" or the replacement theory, which suggests that humans evolved in Africa and migrated to other lands between 56,000 and 200,000 years ago. Some anthropologists also call this theory the "out of Africa II theory." They refer to it as such because it deals with Homo erectus tribes leaving Africa previously, followed by the spreading out of Homo sapiens. The migration took place over tens of thousands of years. The remaining hominids, such as Neanderthals, eventually vanished.
Research seems to confirm the out of Africa theory. DNA evidence made public in 2007 backs up the idea that modern humans are all descended from a group of Homo sapiens who left Africa some 2,000 generations ago, populating modern-day Europe and Asia over the course of thousands of years. The study looked at DNA from Aboriginal Australians and Melanesians from New Guinea and found that the subjects' DNA matched the DNA patterns seen in early humans -- the same genetic qualities already established in the humans who left Africa about 50,000 years ago.
Before the results of the study were unveiled, some had reason to doubt the out of Africa theory because the evidence in Australia was not conclusive enough -- skeletons and other archaeological finds there were quite different from those seen in other lands that make up the migration path the early humans in Africa would have taken when they emigrated. The thinking was that perhaps some of the early arrivals interbred with Homo erectus or there was a second migration from Africa -- either of which would make a common-ancestor for all men and unlikely prospect. The new DNA evidence, however, found no trace of interbreeding with Homo erectus and instead pointed toward the early Australian population sharing the same ancestry as Eurasian populations [source: Science Daily].
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