To shed light on the peopling of South Asia, and the origins of the morphological adaptations there, authors [attached] analyzed whole-genome sequences from 10 Andamanese individuals and compared them with whole-genome sequences of 60 individuals from mainland Indian populations––having different ethnic histories and with publicly available data from other populations. The Andamanese people represent a tribe of aboriginal inhabitants of the Andaman Islands (part of India). The islands are located in the southeastern portion of the Bay of Bengal. Andamanese resemble other Negrito groups in Southeast Asia, i.e. they are a type of pygmy and the only modern population outside certain parts of Sub-Saharan Africa exhibiting steatopygia (having substantial levels of adipose tissue on the buttocks and thighs, not confined to the gluteal regions, but extending to the outside and front of thighs and tapering to the knees).
Similar to pygmies, Andamanese lead a hunter-gatherer lifestype and presumably have lived mostly in isolation for thousands of years. The Andamanese are believed to have arrived in the Andaman Islands in the latest Glacial Maximum, ~26,000 years before the present. By end of the 18th century (when they first came into sustained contact with outsiders), there were an estimated 7,000 Andamanese divided into five major groups––with distinct cultures, separate domains, and mutually unintelligible languages. During the next century, they died in large numbers due to diseases, violence, and loss of territory. Today, there remain only ~400–450 Andamanese, and only two of the remaining five tribes still maintain a steadfast independence, refusing most attempts at contact by outsiders.
Authors of the attached paper show by whole-genome sequencing (WGS) that all Asian and Pacific populations share a single origin and expansion out of Africa, contradicting an earlier proposal of two independent waves of migration. They also discovered that populations from South and Southeast Asia harbor a small proportion of ancestry from an unknown extinct hominin; this ancestry is absent from Europeans and East Asians. Interestingly, the footprints of adaptive selection in genomes of the Andamanese show that characteristic distinctive phenotypes of this population (including very short stature) do not reflect an ancient African origin––but instead result from strong natural selection on genes related to body size.
Nat Genet Sept 2o16; 48: 1066–1070