Q2 mtDNA haplogroup in Oceania

PLoS ONE 7(12): e52022. doi:10.1371/journal.pone.0052022

The Q2 Mitochondrial Haplogroup in Oceania

Chris A. Corser et al.

Many details surrounding the origins of the peoples of Oceania remain to be resolved, and as a step towards this we report seven new complete mitochondrial genomes from the Q2a haplogroup, from Papua New Guinea, Fiji and Kiribati. This brings the total to eleven Q2 genomes now available. The Q haplogroup (that includes Q2) is an old and diverse lineage in Near Oceania, and is reasonably common; within our sample set of 430, 97 are of the Q haplogroup. However, only 8 are Q2, and we report 7 here. The tree with all complete Q genomes is proven to be minimal. The dating estimate for the origin of Q2 (around 35 Kya) reinforces the understanding that humans have been in Near Oceania for tens of thousands of years; nevertheless the Polynesian maternal haplogroups remain distinctive. A major focus now, with regard to Polynesian ancestry, is to address the differences and timing of the ‘Melanesian’ contribution to the maternal and paternal lineages as people moved further and further into Remote Oceania. Input from other fields such as anthropology, history and linguistics is required for a better understanding and interpretation of the genetic data.

Link

Demographic history of Oceania (Wollstein et al. 2010)

frappe analysis on the left: New Guinea Highlanders split at K=4 (light blue), with Polynesian-Fijians remaining aligned with East Asians; at K=5 the specificity of the East Eurasian component in Polynesians-Fijians (teal) is revealed; at K=5 the specificity of Borneo is apparent (red), but there are individuals of clearer East Asian ancestry remaining.

From the paper:

Among the three demographic models examined for the peopling of Near Oceania (Figure 4, models 2a–2c), the model receiving the highest support involves a split of New Guineans from a common European-East Asian (i.e., Eurasian) ancestor population. This finding does not support the southern dispersal hypothesis of separate human migrations from Africa to Near Oceania and to East Asia [33, 34]. The existence of a single ancestral population for all present-day non-Africans is supported, among other genetic evidence, by recent data from the Neandertal genome sequence, indicating that all present-day non-African genome sequences studied(including one from a Papua New Guinean) have equivalent amounts of Neandertal admixture [46].

However, the authors date the split of Near Oceanians from the common Eurasians at 27ky and of East Asians from Europeans at only 18ky. These dates are far too low, in my opinion, as there is evidence that Upper Paleolithic Europeans were already robust versions of modern Caucasoids.

Moreover, if Eurasian unity broke down at 27ky, then where were the Eurasians since the time they acquired "Neandertal admixture" until 27ky?

It is difficult to imagine Eurasians camping in the Near East or Europe (where Neandertals are attested) for tens of thousands of years before starting to split off at 27ky. And indeed, the fact that there are anatomically modern humans from South China and the Levant at around 100ky, make the idea that Eurasians got Neandertal admixture in one place before starting to disperse a few tens of thousands of years ago hard to believe.

I personally don't buy the idea that New Guineans have the same "Neandertal admixture" as Europeans. In fact, I doubt there is any substantial Neandertal admixture in Eurasians at all, and if there is, it is certainly not the 1-4% evenly distributed element across Eurasia that was discovered in the recent paper.

In any case, this issue is peripheral to this paper which offers important new data on the question of Oceanian origins.

Related:

• Bayesian phylogenetics of languages and the timing of Austronesian settlement of the Pacific from Taiwan
• 500K SNP study of Oceanian populations
• Genetic structure of Pacific Islanders
• Polynesians more Asian than Melanesian
• A rare genomic look at Aboriginal Australians

Curr Biol. 2010 Nov 10. [Epub ahead of print]

Demographic History of Oceania Inferred from Genome-wide Data.

Wollstein A, Lao O, Becker C, Brauer S, Trent RJ, Nürnberg P, Stoneking M, Kayser M.

Abstract

BACKGROUND: The human history of Oceania comprises two extremes: the initial colonizations of Near Oceania, one of the oldest out-of-Africa migrations, and of Remote Oceania, the most recent expansion into unoccupied territories. Genetic studies, mostly using uniparentally inherited DNA, have shed some light on human origins in Oceania, particularly indicating that Polynesians are of mixed East Asian and Near Oceanian ancestry. Here, we use ∼1 million single nucleotide polymorphisms (SNPs) to investigate the demographic history of Oceania in a more detailed manner.

RESULTS: We developed a new approach to account for SNP ascertainment bias, used approximate Bayesian computation simulations to choose the best-fitting model of population history, and estimated demographic parameters. We find that the ancestors of Near Oceanians diverged from ancestral Eurasians ∼27 thousand years ago (kya), suggesting separate initial occupations of both territories. The genetic admixture in Polynesian history between East Asians (∼87%) and Near Oceanians (∼13%) occurred ∼3 kya, prior to the colonization of Polynesia. Fijians are of Polynesian (∼65%) and additional Near Oceanian (∼35%) ancestry not found in Polynesians, with this admixture occurring considerably after the initial settlement of Remote Oceania. Our data support a greater contribution of East Asian women than men in the admixture history of Remote Oceania and highlight population substructure in Polynesia and New Guinea.

CONCLUSIONS: Despite the inherent ascertainment bias, genome-wide SNP data provide new insights into the genetic history of Oceana. Our approach to correct for ascertainment bias and obtain reliable inferences concerning demographic history should prove useful in other such studies.

Link