Thursday, October 20, 2011

Lock of hair pins down early migration of Aborigines

Using tiny genetic clues found in a 100-year-old lock of Australian Aboriginal hair, an international team of researchers has determined the human migration to Australia took place far earlier than originally thought.  According to DNA analysis from the 1923 Aboriginal hair, indigenous Australians were first genetically isolated around 70,000 years ago, some 46,000 years before populations moved out of Africa and the Middle East to colonize Europe and Asia.

In order to call this dominant theory into question, researchers first had to map and genotype the genome of the Aboriginal hair.  The team then developed a method using patterns of allele frequency and linkage equilibrium to estimate migration rate and divergence times between populations sampled: Aborigine, East Asian, European, and African.  The results point to a longer divergence time between Aboriginal Australians and East Asians than between East Asians and Europeans, suggesting an early wave of migration of Aboriginal Australians and a later expansion wave into Asia and Europe.  Researchers also were able to track levels of the archaic human Denisovan DNA in the different populations and found a much higher concentration in the Aboriginal sample, suggesting a long period of inbreeding due to isolation (isolation resulting from an early migration).

Of course questions and doubts remain (to what extent is one Australian Aborigine in 1923 representative of an entire evolutionary history?), but these pioneering techniques are already shedding light on a very uncertain time in human prehistory.

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