The Himalayas: Barrier and conduit for gene flow.
Gayden T, Perez A, Persad PJ, Bukhari A, Chennakrishnaiah S, Simms T, Maloney T, Rodriguez K, Herrera RJ.
Abstract
The Himalayan mountain range is strategically located at the crossroads of the major cultural centers in Asia, the Middle East and Europe. Although previous Y-chromosome studies indicate that the Himalayas served as a natural barrier for gene flow from the south to the Tibetan plateau, this region is believed to have played an important role as a corridor for human migrations between East and West Eurasia along the ancient Silk Road. To evaluate the effects of the Himalayan mountain range in shaping the maternal lineages of populations residing on either side of the cordillera, we analyzed mitochondrial DNA variation in 344 samples from three Nepalese collections (Newar, Kathmandu and Tamang) and a general population of Tibet. Our results revealed a predominantly East Asian-specific component in Tibet and Tamang, whereas Newar and Kathmandu are both characterized by a combination of East and South Central Asian lineages. Interestingly, Newar and Kathmandu harbor several deep-rooted Indian lineages, including M2, R5, and U2, whose coalescent times from this study (U2, >40 kya) and previous reports (M2 and R5, >50 kya) suggest that Nepal was inhabited during the initial peopling of South Central Asia. Comparisons with our previous Y-chromosome data indicate sex-biased migrations in Tamang and a founder effect and/or genetic drift in Tamang and Newar. Altogether, our results confirm that while the Himalayas acted as a geographic barrier for human movement from the Indian subcontinent to the Tibetan highland, it also served as a conduit for gene flow between Central and East Asia.
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2 comments:
IIRC, the archaeology shows the first human presence in Tibet at about 30 kya. Of course, new finds could alter the conclusion, but this data point ought to temper a reading of TMCRA estimates of >40 kya or >50 kya as indicating a modern human presence in Tibet that is that old.
"suggest that Nepal was inhabited during the initial peopling of South Central Asia".
To me the distribution of haplogroups in South and East Asia indicates strongly that Nepal (or more correctly the Siwalik Range) was the main ancient Homo sapiens route east. The migration was certainly not 'coastal' in any meaningful use of the term. That would explain the 'Newar and Kathmandu harbor several deep-rooted Indian lineages'.
"Our results revealed a predominantly East Asian-specific component in Tibet and Tamang, whereas Newar and Kathmandu are both characterized by a combination of East and South Central Asian lineages".
Yes. The Himalayas represent a very steep cline the South and East Asian phenotype, with the cline being formed by a southward moving Mongoloid phenotype rather than a northward moving South Asian phenotype.
"our results confirm that while the Himalayas acted as a geographic barrier for human movement from the Indian subcontinent to the Tibetan highland, it also served as a conduit for gene flow between Central and East Asia".
Including a very ancient human movemetn east? I have long believed that Y-DNA C and mt-DNA N moved east along such a route.
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