Comments on: Present genetic variation is a weak guide to past genetic variation

By: Pat Shipman

Pat Shipman — Tue, 21 Jun 2011 19:53:51 +0000

There is another issue here. If 90+% of all mtDNA lineages that have existed once are now extinct, WHY would we think that a sample of fewer than 1000 individuals would adequately sample all the variability that existed in the past? The same problem arose comparing the mtDNA of a small number of Neandertals with a database of a few thousand individuals from different modern human populations. I think this question of adequate sampling is much more complex than has been assumed in the past, Maybe 846 mtDNA samples from Myanmar is difficult to obtain & analyze, but is it adequate?

By: Vitasta

Vitasta — Fri, 17 Jun 2011 03:21:03 +0000

Agree with you about past patterns of genetic variation wrt frequency and spread. But there is an inherent temporal directionality to uniparental inheritance that has merit imo; in other words, the
derivation of M31 -> M31a -> M31a1 is meaningful phylogeographically in relating groups today.

If ASI has been as thoroughly turned over as it seems to be the in the South Asian context I really
wonder if we can ever hope to find any trace of the original OOA outflow. Other than perhaps in
future aDNA work. I am not holding my breath!

By: ohwilleke

ohwilleke — Thu, 16 Jun 2011 16:47:14 +0000

Given the fact that the dates confirm each other, the land bridge date of 22-18kya seems pretty reliable and the mtDNA method used seem to be confirmed.

This puts the settlement of the Andaman Islands at least 20,000 years after the settlement of Papua New Guinea and Australia.

And, while they may not be “living fossils” from the “Out of Africa” era, there aren’t many populations that have pretty definitively been isolated that long. In addition to Papuans and Australian aborigines, you have the Jomon (ca. 30,000 years ago) of Japan although there seems to have been minor admixture in at least the related Norther Ainu with Siberian populations, and the segregation of sub-polar New World populations from Eurasian populations of similar time depth to the Andamanese (since they relied on the same land bridge effect).

The only other populations I can think of that seem to have pretty definitively pre-LGM coherence are a substratum of Tibetans, the Bushmen, and the Pygmies. In other cases, that possibility of material post-LGM resuffling is immense or certain.