Tuesday, October 24, 2006

The uniqueness of Andaman Islanders

The authors use 9 autosomal STR markers to examine the affinities between The Andaman Islanders and Indians and Africans. I am unsure as to why they didn't examine other neighboring populations (Thailand, Indonesia, Burma), but maybe because in their previous study on Y-chromosome and mt-DNA they find the closest affinity with Indians. Anyway, they find/confirm that the Andaman Islanders are genetically very unique and may trace their ancestry to a first wave of humans out of Africa.

Unique origin of Andaman Islanders: insight from autosomal loci

K. Thangaraj, G. Chaubey, A. G. Reddy, V. K. Sing and L. Singh

Journal of Human Genetics Volume 51, Number 9 / September, 2006

Abstract: Our mtDNA and Y chromosome studies lead to the conclusion that the Andamanese “Negrito” mtDNA lineages have survived in the Andaman Islands in complete genetic isolation from other South and Southeast Asian populations since the initial settlement of the region by the out-of-Africa migration. In order to obtain a robust reconstruction of the evolutionary history of the Andamanese, we carried out a study on the three aboriginal populations, namely, the Great Andamanese, Onge and Nicobarese, using autosomal microsatellite markers. The range of alleles (7–31.2) observed in the studied population and heterozygosity values (0.392–0.857) indicate that the selected STR markers are highly polymorphic in all the three populations, and genetic variability within the populations is significantly high, with a mean gene diversity of 77%. The Andaman “Negrito” populations do not show particular affinities either with the African populations or with the Indian populations, confirming their unique origin. In contrast, Nicobarese show close affinities with the Southeast Asian populations, suggesting their recent entry in the Islands.

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