for National Geographic News
Where did we come from?
Part of the answer may lie in a new study that suggests Australian Aborigines and Europeans share the same roots—and that both emerged from a wave of African migrations more than 50,000 years ago.
(Related: "Skull Is First Fossil Proof of Human Migration Theory, Study Says" [January 12, 2007].)
Both populations can be traced back to the same founders, according to study co-author Toomas Kivisild of the University of Cambridge.
The finding may strike another nail into the coffin of the "multiregional" hypothesis—the idea humans evolved separately in different parts of the world.
The scientists took blood samples from modern Aborigines and Asian populations and compared their DNA. The researchers then traced the family tree backward through their mitochondrial DNA (the female lineage) and Y chromosome DNA (the male lineage).
"We could trace back to where the branches join by counting mutations in the DNA," said study co-author Phillip Endicott of the University of Oxford.
Assuming an average DNA mutation rate, the scientists calculated how many years had passed since the populations split.
Boost for "Out of Africa"
All of the Australian lineages fell within four DNA branches, which are associated with the exodus of modern humans from Africa between 50,000 and 70,000 years ago.
As the theory suggests, Africans are believed to have migrated on foot to Eurasia, the large landmass where the European and Asian continents join. The descendants of these migrants may have been able to cross a land bridge between Australia and neighboring New Guinea when sea levels were lower 50,000 years ago (map of the region).
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