February 26, 2016

No Y-chromosomes of recent Indian origin in Australians

Current Biology http://dx.doi.org/10.1016/j.cub.2016.01.028

Deep Roots for Aboriginal Australian Y Chromosomes

Anders Bergström et al.

Australia was one of the earliest regions outside Africa to be colonized by fully modern humans, with archaeological evidence for human presence by 47,000 years ago (47 kya) widely accepted [ 1, 2 ]. However, the extent of subsequent human entry before the European colonial age is less clear. The dingo reached Australia about 4 kya, indirectly implying human contact, which some have linked to changes in language and stone tool technology to suggest substantial cultural changes at the same time [ 3 ]. Genetic data of two kinds have been proposed to support gene flow from the Indian subcontinent to Australia at this time, as well: first, signs of South Asian admixture in Aboriginal Australian genomes have been reported on the basis of genome-wide SNP data [ 4 ]; and second, a Y chromosome lineage designated haplogroup C∗, present in both India and Australia, was estimated to have a most recent common ancestor around 5 kya and to have entered Australia from India [ 5 ]. Here, we sequence 13 Aboriginal Australian Y chromosomes to re-investigate their divergence times from Y chromosomes in other continents, including a comparison of Aboriginal Australian and South Asian haplogroup C chromosomes. We find divergence times dating back to ∼50 kya, thus excluding the Y chromosome as providing evidence for recent gene flow from India into Australia.



Andrew Millard said...

Zero successes on 13 trials has a 95% confidence region of 0% to 25% on the underlying true proportion of successes. Because the sample size is small these results are not strong evidence against gene flow and could be compatible with significant gene flow.

terryt said...

"We find divergence times dating back to ∼50 kya, thus excluding the Y chromosome as providing evidence for recent gene flow from India into Australia".

Surely that has long been obvious to anyone who cared to actually look at the evidence. Y-DNA C looks to have been the first Y-DNA across Wallace's Line, beating Y-DNA K by some years at least. Australian Y-DNA C is C1b2b with its closest relation being C1b2a centred on southern Wallace, east of Wallace's line. That's exactly what we would expect. Indian Y-DNA C is C1b1a1 with its closest relation being C1b1a2 centred on Borneo. That is not quite what we would expect if Australian C had come via India. C1b splits into two, one branch each side of Wallace's Line. What's more Indian C1b1a splits into two, one branch centred on Bangladesh and the other in northwest India. That looks suspiciously as though it became isolated at each end of the Ganges. In other words Indian Y-DNA C came from the east after members of the haplotype had developed boats capable of crossing Wallace's Line. That's what I have been trying to point out for years now.

terryt said...

Further to the above. I presume the Y-DNA the authors have labelled 'Papua New Guinea Y-chr' is the Y-DNA C that almost certainly arose in Southern Wallacea and at some later time spread to western New Guinea and along the northern coastline and eventually out into the Pacific with the Austronesian speakers.

Nathan said...

Some time back when that paper came out claiming Indian admixture into Australian Aborigines around 4000 years ago, I strongly suspected the authors made an error and that if there was genetic affinity between Indian populations and Australians, the common ancestrors would have been 40,000 years ago. There just isn't any cultural link between India and Australia's Aborigines .

eurologist said...

There we have it again: a male lineage divergence time of ~55,000 ya in Australia (and Papua New Guinea), anchored with a 45,000 ya known sample (i.e., fairly accurate). Even the divergence time between most Papuans and Australians is ~50 ky.

Adding to this that most extant male and female European and SW / W Asian lineages derive from S / SE Asia, it is clear that the UP revolution, that had AMHs suddenly appear ~55 - 50 ky ago in the Levant, Europe, and Siberia and for the first time there overwhelm native ancient humans, started in SE Asia. As much as we are all Africans, people outside of Africa (and to a significant, but smaller percentage also Africans) are also all (very early) SE Asians. And finally, that explosion took a long time in the making and could not possibly have started with a few thousand ooA people leaving that continent just a few thousand years before then, while squeezing through hostile W and S Asia in the most impossible climatic times.

terryt said...

I agree with Eurologist completely. It became reasonably obvious to me when I first looked at the McDonald maps of 2005 that both mt-DNA R and Y-DNA K (which included N'O and P'Q) had originated in SE Asia. I was strongly criticised whenever I suggested it to be so.

eurologist said...


Yes, I do remember, and even I have been and still am critical with regard to some aspects. If ooA took place ~120,000 - 105,000 ya, we have a time gap of ~60,000 years that needs to be "taken care of," both in terms of the evolutionary lineage trees, and the location of AMHs outside Africa.

I have some ideas about the male CT lineages and the female L subgroups, but I think it is fair to say that no one (I know of) has built a compelling picture of the time frames and locations involved - which by necessity also include SW and S Asia and NE Africa.

terryt said...

I came to the conclusion some time ago that Y-DNA CT and mt-DNA MN spread considerably through the semi-open grasslands of northeast Africa, Southwest Asia and into Central Asia before being greatly reduced in population numbers, isolating several populations in which the root haplotypes coalesced. Both Y-DNA C and D surely coalesced somewhere on the northeast margin of the Tibetan Plateau, or perhaps slightly further south (especially in the case of Y-DNA D and mt-DNA M), while Y-DNA F along with several branches of mt-DNA N coalesced somewhere on the Anatolian/Iranian Plateau. The remaining mt-DNA Ns also became confined to the northeastern Tibetan Plateau and then moved south with Y-DNA C1b to reach Australia. I see nothing that contradicts this possibility and very little to suggest that South Asia was involved at all in any early modern human expansion.