Monday, May 12, 2008

The impact of the Austronesian expansion: Admiralty Islands

A new study examines again the Austronesian expansion from the view of migrating Austronesian speakers reaching Melanesia.

One problem with these studies is that they do clearly differentiate between Austronesian and Malayo-Polynesian expansion. Even if we grant that Austronesian speakers originated in Taiwan, as the new study claims, it is highly doubtful that the Malayo-Polynesian expansion radiated from that region. There are no Malayo-Polynesian languages in Taiwan, and the general distribution of the linguistic branches do not jibe with a Taiwan location.

Another thing is we should not assume anything about the "race" of the Austronesian speakers, or for that matter the "Melanesians" back in the Neolithic period when these expansions occurred.

Austronesian speakers in the Pacific -- Micronesians, Melanesians and Polynesians -- for example, all have significant percentages of Y chromosome C2 haplogroup. In some Polynesian areas, C2 is the dominant haplotype. However, C2 has not been found in Taiwan so far.

Paul Kekai Manansala

Mol Biol Evol. 2008 Apr 3

The impact of the Austronesian expansion: evidence from mtDNA and Y-chromosome diversity in the Admiralty Islands of Melanesia.

Department of Forensic Molecular Biology, Erasmus University Medical Center Rotterdam, The Netherlands.

The genetic ancestry of Polynesians can be traced to both Asia and Melanesia, which presumably reflects admixture occurring between incoming Austronesians and resident non-Austronesians in Melanesia before the subsequent occupation of the greater Pacific; however, the genetic impact of the Austronesian expansion to Melanesia remains largely unknown. We therefore studied the diversity of non-recombining Y-chromosomal (NRY) and mitochondrial (mt) DNA in the Admiralty Islands, located north of mainland Papua New Guinea, and updated our previous data from Asia, Melanesia and Polynesia with new NRY markers. The Admiralties are occupied today solely by Austronesian-speaking groups, but their human settlement history goes back 20,000 years prior to the arrival of Austronesians about 3,400 years ago. On the Admiralties we found substantial mtDNA and NRY variation of both Austronesian and non-Austronesian origin, with higher frequencies of Asian mtDNA and Melanesian NRY haplogroups, similar to previous findings in Polynesia, and perhaps as consequence of Austronesian matrilocality. Thus, the Austronesian language replacement on the Admiralties (and elsewhere in Island Melanesia and coastal New Guinea) was accompanied by an incomplete genetic replacement that is more associated with mtDNA than with NRY diversity. These results provide further support for the "Slow Boat" model of Polynesian origins, according to which Polynesian ancestors originated from East Asia but genetically mixed with Melanesians before colonizing the Pacific. We also observed that non-Austronesian groups of coastal New Guinea and Island Melanesia had significantly higher frequencies of Asian mtDNA haplogroups than of Asian NRY haplogroups, suggesting sex-biased admixture perhaps as a consequence of non-Austronesian patrilocality. We additionally found that the predominant NRY haplogroup of Asian origin in the Admiralties (O-M110) likely originated in Taiwan, thus providing the first direct Y-chromosome evidence for a Taiwanese origin of the Austronesian expansion. Furthermore, we identified a NRY haplogroup (K-P79, also found on the Admiralties) in Polynesians that most likely arose in the Bismarck Archipelago, providing the first direct link between northern Island Melanesia and Polynesia. These results significantly advance our understanding of the impact of the Austronesian expansion and of human history in the Pacific region.