Inland post-glacial dispersal in East Asia revealed by mitochondrial haplogroup M9a'b

Abstract

BackgroundArchaeological studies have revealed a series of cultural changes around the Last Glacial Maximum in East Asia; whether these changes left any signatures in the gene pool of East Asians remains poorly indicated. To achieve deeper insights into the demographic history of modern humans in East Asia around the Last Glacial Maximum, we extensively analyzed mitochondrial DNA haplogroup M9a'b, a specific haplogroup that was suggested to have some potential for tracing the migration around the Last Glacial Maximum in East Eurasia.ResultsA total of 837 M9a'b mitochondrial DNAs (583 from the literature, while the remaining 254 were newly collected in this study) pinpointed from over 28,000 subjects residing across East Eurasia were studied here. Fifty-nine representative samples were further selected for total mitochondrial DNA sequencing so we could better understand the phylogeny within M9a'b. Based on the updated phylogeny, an extensive phylogeographic analysis was carried out to reveal the differentiation of haplogroup M9a'b and to reconstruct the dispersal histories.ConclusionsOur results indicated that southern China and/or Southeast Asia likely served as the source of some post-Last Glacial Maximum dispersal(s). The detailed dissection of haplogroup M9a'b revealed the existence of an inland dispersal in mainland East Asia during the post-glacial period. It was this dispersal that expanded not only to western China but also to northeast India and the south Himalaya region. A similar phylogeographic distribution pattern was also observed for haplogroup F1c, thus substantiating our proposition. This inland post-glacial dispersal was in agreement with the spread of the Mesolithic culture originating in South China and northern Vietnam.

Revisiting the role of the Himalayas in peopling Nepal: insights from mitochondrial genomes

“…3 However, the observed gene flow from northeast India suggests genetic contribution, albeit limited, from this region, a scenario echoing the proposed inland dispersal route. 50 In this spirit, our findings complete the understanding of the origin of the Nepalese and the way how the East Eurasian genetic components had been introduced into Nepal. Taking into account the previous observation on Y chromosome, 4 now it is convincing that the East Eurasian had entered Nepal across the Himalayas around 6 kya, a scenario in good agreement with the previous findings from linguistics and archeology.…”

“…49 Previous studies have observed substantial East Eurasian genetic components in the Nepalese populations; 4,5 however, it remains controversial whether the East Eurasian lineages have been introduced into Nepal from Tibet directly (across the Himalayas) 4,6 or via northeast India. 5,8,50 By extensively analyzing the mtDNA variation in Nepal, Tibet, northern India populations, our observations, based on the principle component analysis, Fst and admixture estimation, revealed the closer genetic affinity between the Nepalese and the Tibetans, and this result was further substantiated by the median networks, (Figures 4 and 5) in which most of the Nepalese mtDNAs prevalent among northern Asian populations shared the haplotypes with the Tibetans at root level or branched off directly from the nodes consisting almost exclusively of the Tibetan lineages. Our results strongly suggest that most of the East Eurasian maternal components identified in the Nepalese were introduced directly from Tibet, 4,6 and the time estimation results further date that this peopling scenario plausibly occurred about 6 kya.…”

Long-term genetic stability and a high-altitude East Asian origin for the peoples of the high valleys of the Himalayan arc

“…The derived EPAS1 haplotype was recently shown to have originated in the Denisova genome and its presence in the human genome represents a recent archaic introgression (36). Consequently, the subsequent selection of this haplotype in humans is difficult to model using genetic data from living populations, and dates ranging from 2,750 ya to 18,250 ya have been proposed (13,17,38).…”

“…Currently available archaeological and osteological data and genetic data from modern-day populations have been used to support contrasting hypotheses of South Asian (9-11), Central Asian (12), lowland Southeast Asian (13), and high-altitude East Asian (7,8) origins for the earliest Himalayan inhabitants, and there is likewise little agreement regarding subsequent regional population history (12,14). Successful permanent habitation of high-altitude environments requires numerous physiological adaptations, and recent genetic studies have identified robust signals of positive natural selection underlying adaptations to hypoxia in Tibetans (15)(16)(17) and in the Sherpa (18), an ethnic group that migrated from the eastern Tibetan plateau to Nepal 400-600 y ago (ya) (19).…”

Lactase persistence may have an independent origin in Tibetan populations from Tibet, China

“…18,19 The Neolithic genetic components from Northern China were revealed to contribute substantially to the current gene pool of Tibetans. [18][19][20] Nevertheless, the susceptible alleles for LP in those surrounding populations were not introgressed into Tibetan populations via the prehistorical and historical migrations. Taken together, we propose that the LP in Tibetans is likely to have an independent origin.…”