The matrilineal ancestry of Nepali populations

The maternal ancestry of Nepal is a mixture of the South and East-Asian population

It is widely accepted that the modern human originated in Africa around 200 000 years ago (KYA) and migrated out of Africa between 60 and 70 KYA. Several populations arose in this process, and each has its own evolutionary history. Genetic drift, endogamy, admixture, isolation, and natural selection are a few evolutionary processes that have contributed to genetic diversity among human populations worldwide, including susceptibility and resistance to genetic diseases, infectious diseases, therapeutic response to drugs, and other conditions. Understanding these phenomena is much more relevant in a country like Nepal, which has one of the world's richest ethnic, cultural, linguistic, and social diversity and harbors several anthropologically well-defined populations. In simple terms, there are populations in Nepal that are phenotypically similar to East Asians (Mongolians/ Tibetans/ Chinese/ southeast Asians); some are similar to Europeans (West Eurasian), and some are similar to Southeast Asians. Broadly, Nepali speaks two major families of languages: Indo-European and Tibeto-Burman language. To understand Nepal's peopling, its ancient history, and its genetic diversity, we conducted a high-throughput genetic (DNA) study of several Nepalese populations.

In Newar, the majority, 51%, belong to East Asian ancestry, whereas 36% were assigned to South Asian origin, and 13% belonged to West Eurasian ancestry. Similarly, in Magar, 54% belong to East Asia, whereas 38% and 5% belong to South Asia and West Eurasia. Likewise, in Brahmin, the bulk, 60%, belongs to South Asian origin, followed by 25% and 14.6% of East Asian and West Eurasian origin. Among the Nepalese populations, we observed the highest frequency of East Asian ancestry in Sherpa (94.3%), followed by Tharu-CI (68.4%), Tamang (65.9%), and so on.

Sherpa, who inhabit the highest mountainous regions close to the Tibetan plateau, remained genetically distant from other Nepalese populations, suggesting a low level of admixture from surrounding Nepalese populations. In fact, Sherpa were genetically similar to Tibetans. Interestingly, we found a signature of early admixture between several Nepalese populations, including some of the Himalayan groups from Uttarakhand, India. Even the Brahmin, Indo-European-speaking populations showed 25% east Asian ancestry. The majority of the Nepalese Tibeto-Burmans were different from the Sherpas or Tibetans. Except for a few admixtures with the Tibetans, most Nepalese Tibeto-Burman show shared ancestry with populations from Northeast India, Myanmar, and Thailand. We traced the common ancestors of these populations to the Neolithic immigrants from China ~8 thousand years ago. We also looked into the probable migration route and the time when the carrier of the East Asian lineages entered Nepal. Despite recent admixture with the northeast Indians, we found that most Nepalese Tibeto-Burmans entered Nepal from China via southeastern Tibet around 3.8 to 6 thousand years ago. Overall, geographical isolation, admixture with surrounding groups, and cultural fragmentation have significantly shaped the current East Asian maternal diversity in the Himalayan region.

full article link: https://link.springer.com/article/10.1007/s00439-022-02488-z