It was a good idea to address the mtDNA data as well since we already have an overview over Himalayan ethnic minority mtDNA profiles by now.JCA wrote:Four out of their ten Tibetans from Gansu belong to mtDNA haplogroup D4 and two belong to M9a1b1. The sample size is very small (not to mention the question of intentional selection for rare or phylogenetically informative haplogroups that we have suspected in the case of the subset of the Bhutanese sample analyzed by Hallast et al. 2014), so it may not be a good reflection of reality, but it does remind me of a contrast that I have noticed between samples of Tibetan mtDNA in some early studies, with some having M9 (or "M*") as predominant haplogroup and others having D4 (or "D") as predominant haplogroup. The age estimates that I have seen so far seem to indicate that D4 is probably the older haplogroup, with the predominance of M9 in some samples of Tibetans being due to a relatively recent founder effect, drift, or selection.
The major D4 clades are IMO not necessarily old in mainstream Tibetans. According to Qi et al. 2013. there are just...
- D4-16129 (possibly predominately D4a-16129 back mutation judging from fig. S2 of Derenko et al. 2010)
Of these, D4j3 is just about 8800 years old according to the calculations of Qi et al. 2013. That's about the same estimated age as that of their M9a1a and M9a1b1 Tibetan samples. By contrast, their age estimates concerning certain branches of hgs A, C, F and G are higher. And the latter turned out to be common in Himalayan ethnic minorities of Nepal and parts of the India which neighbour Nepal. I.e., A, C, F and G could be remnants of pre-Tibetan populations assimilated by Tibetans, whereas most D4j3 and M9 hts might have arrived together with mainstream Tibetan culture and thereafter.
Derenko et al. 2010: "Origin and Post-Glacial Dispersal of Mitochondrial DNA Haplogroups C and D in Northern Asia"; doi: 10.1371/journal.pone.0015214
Qi et al. 2013: "Genetic Evidence of Paleolithic Colonization and Neolithic Expansion of Modern Humans on the Tibetan Plateau"; doi: 10.1093/molbev/mst093