Mongolian tribes cluster with East Asians, closely related to the Japanese

New paper behind paywall Whole-genome sequencing of 175 Mongolians uncovers population-specific genetic architecture and gene flow throughout North and East Asia, by Bai et al Nature Genetics (2018).

Interesting excerpts (emphasis mine):

Genome sequencing, variant calling, and construction of the Mongolian reference panel. We collected peripheral blood with informed consent from 175 Mongolian individuals representing six distinct tribes/regions in northern China and Mongolia, including the Abaga, Khalkha, Oirat, Buryat, Sonid, and Horchin tribes.

Population genetic structure. a, PCA of Mongolian individuals and 1000G samples. Mongolians fill a large, less characterized gap between Admixed/Native Americans and other East Asians in the 1000G project. b, PCA of Mongolians and East Asians of 1000G. The abbreviations of EAS populations were used from reference 11.

The fixation index (FST) was used to estimate pairwise genetic differentiation among our Mongolian samples and 26 modern human populations selected from 1000G (…) the Mongolian tribes cluster with East Asian groups. The Mongolian populations show the smallest differentiation from the CHB, and FST values increase relative to the magnitude of geographical separation. The Buryat are the most differentiated tribe compared with other East Asians (1.82–2.97%), while the Horchin are the least (0.25–1.35%). All tribes are closer to the Japanese (JPT) than the CHS with the exception of the Horchin. Among the tribes, the Abaga, Khalkha, Oirat, and Sonid show the least differentiation from one another (FST < 0.15%)

A PCA places the Mongolians in close genetic proximity to a group of North Asian Siberians, including Altaians, Tuvinians, Evenki, and Yakut, indicating that the Mongolian whole-genome variation panel could be a better proxy for these groups than any populations currently in the 1000G panel

The most common Y-chromosome haplogroups are from the C3 sublineage (41.67%), including C3c (29.17%) and C3b (12.50%), followed by haplogroup O (23.61%), and haplogroup N (18.06%) (…) While haplogroups C and O are primarily restricted to Asia, haplogroup N is present at high frequency in Finns (60.5%), at low frequency in non-Mongolian East Asians (< 1%), and virtually absent throughout the remainder of European and African samples in 1000G

Comparison with Finns

Distribution of D-values from D-test under the model of [EAS, Mongolians, X, chimpanzee], where X represents the test population and chimpanzee serves as an outgroup. The positive D-value (Z > 3) indicates that the test population (X) is closer to Mongolians than to EAS. The whiskers correspond to range, and the dots to individual data points, box limits are the upper and lower quartiles. The n in each boxplot is 30. All abbreviations of populations in the figure were used from reference 11.

Of the populations included in our study, Mongolians share the second-highest level of IBD with the Finnish people (FIN), behind only Northern Han Chinese (CHB). While Mongolians share more IBD with Europeans (EUR) as a whole compared with other non-EAS people (Fig. 4b), removal of Finns from the Europeans drops the level of sharing to as low as that with South Asians (SAS) or Admixed American (AMR).

There is considerable geographic separation between modern-day Mongolians and Europe. The positive D-statistic that reveal gene flow between Mongolians and Europeans (Fig. 4c), and the high degree of IBD sharing with Finnish people in particular suggest that complex admixture may have occurred throughout northeastern Europe and Siberia. To see whether Mongolians represent the ethnic group in East Asia with the highest level of gene flow with Finnish people, we calculated a D-statistic for each set of populations [Mongolians, X, FIN, Yoruba (YRI)], where X represents a population from Siberia or Northern Canada. Most of the populations reveal an imbalance in allele frequencies that suggests gene flow with Finns (D >0, Z >3), but the greatest imbalance is observed between Siberians/Northern Canadians and Finnish, rather than between Mongolians and Finns. This pattern indicates that northern Asian populations interacted across large geographic ranges.

6 migration events, from the supplementary materials.

I guess the 1000G does not have northern Eurasian groups, because the IBD map and values would be lightening up with Palaeo-Siberian peoples