Genetic and linguistic borders in the Himalayan Region

There are a number of competing theories about the origins of the Himalayan peoples. These theories are largely based on linguistic and/or archaeological findings, sometimes supported by the results of small-scale genetic studies. A large-scale, ethnolinguistically-informed genetic study of the greater Himalayan region might provide a definitive model for historical population events in this region, and that is why the current study was undertaken.The geographical area of the present-day states of Nepal and Bhutan could have served as ancient corridors for human migration through the Himalayas despite their geographical position immediately south of the highest land barrier. The findings also raise the question as to whether the southern slopes of the Himalayas could have harboured a myriad of refuge areas for the ancestral Tibeto-Burman population(s) during the last glacial maximum. Alternatively, if the multitude and diversity of language communities found in these countries is a reliable indication, they could be an ancient source of genetically differentiated populations and languages. A detailed genetic study of the Himalayan region, therefore, may not only provide insights into the uniqueness and antiquity of its residents, but may also shed light on the peopling of the Himalayas and eastern Asia in general.Using genetic data from 15 autosomal Short Tandem Repeat (STR) loci, we provide evidence that there is clear congruence between language and genetics. Populations speaking a language belonging to the Tibeto-Burman language family are genetically more similar to each other than to populations speaking a language belonging to the Indo-European language family. On the basis of language differences we can draw a linguistic boundary roughly running from east to west, just south of the border between India and Bhutan and through southern Nepal. A genetic boundary can be reconstructed along nearly the same route. We conclude from all these analyses that the populations of Nepal and Bhutan are likely to have originated outside their current locations, in regions where their language families are spoken, but need further work to suggest more precise origins.