Saturday, 16 February 2008
Out of Africa: Andaman tribes just 10,000 year old
February 14, 2008
By Syed Akbar
Hyderabad, Feb 13: Man settled on the picturesque Andaman islands 10,000 to 24,000 years ago and not 45,000 to 50,000 years ago as earlier believed.
Research studies based on population genetics by the Anthropological Survey of India showed that human settlement on Andaman islands was a relatively recent phenomenon, 24,000 years old at the most. This negates the popular belief that early humans migrated from Africa between 45,000 and 50,000 years ago and settled in Andamans before fanning out to other places including Myanmar and India.
Anthropological Survey of India director-in-charge Dr VR Rao told this correspondent that "the migration of people to Andaman islands took place tentatively around 24,000 years ago." The ASI scientists came out with the observation following an investigation of deep structure of mitochondria DNA sub groups M31, which is Andaman specific and M32 which is India specific. They used whole-genome sequencing methods as part of the study.
The mtDNA contains ancient signature of genes that are passed from mother to child. A study of mtDNA reveals when and how early humans migrated from Africa and settled across the Earth.
India, because of its strategic location on the proposed corridor of human movement from Africa to Australia, holds the key to the understanding of early human prehistory. Genetic studies conducted earlier, based on mitrochondrial DNA, showed that the relative isolation of the late Pleistocene
colonisers, and the physically isolated Andaman Island populations was because of an early split between populations settled along the coast of Indian Ocean.
"The identification of a so far unnoticed rare polymorphism shared between these two lineage suggests that they are actually sister groups within a single haplogroup, M31'32. The enhanced resolution of M31 allows for the inference of a more recent colonisation of the Andaman Islands than previously suggested, but cannot reject the very early peopling scenario," Dr Rao said.
The ASI study further demonstrated a widespread overlap of mtDNA and cultural markers between the two major language groups of the Andaman archipelago. "Given the "completeness" of the genealogy based on whole genome sequences, and the multiple scenarios for the peopling of the Andaman Islands sustained by this inferred genealogy, our study hints that further mtDNA based phylogeographic studies are unlikely to unequivocally support any one of these possibilities," he said.
According to Dr Rao, the significance of the new finding is in terms of understanding the earliest genomic foot prints in the subcontinent. The implications are relevant in evolutionary biology. Adaptive traits which have implications in health and disease and their variation across human populations, can now be in a perspective.
He said the earlier Andamanese were known sea farers. "The story of human migrations is very complex. Even you go to Homo erectus stage, we have very complex scenario of migrations... Nevertheless, imagine all life forms sequencing of whole genomes is available," he said.
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