November 14, 2010

Austronesians in Nias

Mol Biol Evol (2010) doi: 10.1093/molbev/msq300

Unexpected island effects at an extreme: reduced Y-chromosome and mitochondrial DNA diversity in Nias

Mannis van Oven et al.

The amount of genetic diversity in a population is determined by demographic and selection events in its history. Human populations which exhibit greatly reduced overall genetic diversity, presumably resulting from severe bottlenecks or founder events, are particularly interesting, not least because of their potential to serve as valuable resources for health studies. Here, we present an unexpected case, the human population of Nias Island in Indonesia, that exhibits severely reduced Y chromosome (NRY) and to a lesser extent also reduced mitochondrial (mt)DNA diversity as compared with most other populations from the Asia / Oceania region. Our genetic data, collected from more than 400 individuals from across the island, suggest a strong, previously undetected bottleneck or founder event in the human population history of Nias, more pronounced for males than for females, followed by subsequent genetic isolation. Our findings are unexpected given the island's geographic proximity to the genetically highly diverse Southeast Asian world, as well as our previous knowledge about the human history of Nias. Furthermore, all NRY and virtually all mtDNA haplogroups observed in Nias can be attributed to the Austronesian expansion, in line with linguistic data, and in contrast with archaeological evidence for a pre-Austronesian occupation of Nias that, as we show here, left no significant genetic footprints in the contemporary population. Our work underlines the importance of human genetic diversity studies not only for a better understanding of human population history, but also because of the potential relevance for genetic disease mapping studies.



Ponto said...

No significant footprints, so they say.

It would be interesting to have genomic samples of those people and compare them with other peoples in the vicinity of Nias island. It could just be that the Nias Islanders may be exactly the same as their neighbors who do have the requisite footprints of pre Austronesian speaking occupants.

I think the study based on Y chromosome and mtDNA haplogroups is somewhat premature. How do they know that the islanders don't have the rest of their genome from the pre Austronesian speaking occupants? They don't.

ren said...

Ponto, a quarter of the mtDNA is listed as "Other", so the aboriginal element on Nias is likely not small.

Andrew Oh-Willeke said...

Is it really that implausible that the Austronesians wiped out pre-Austronesians on an isolated island on the fringe of Indonesia where everyone speaks an Austronesian language?

If Y-DNA and mtDNA signatures are that strong, I'd be stunned if there was a very large contribution in the rest of their DNA from non-Austronesian sources, and if there is a little, it is probably something that was present in the original Austronesian founder group from pre-arrival admixture.

Reaching this conclusion based just on Y-DNA or just on mtDNA would be premature, but when you have both and they confirm each other, you set a low upper floor on what you can expect to find in the rest of the genome.