Saturday, January 24, 2009

Two new studies on Austronesian expansion, peopling of Pacific

There are a couple of linked articles appearing in the latest edition of Science bearing on the peopling of the Pacific including the Austronesian expansion. I have not read the full articles yet, but have posted the abstracts below.

The first traces the a gut pathogen known as Helicobacter pylori suggesting that different Austronesian language branches are linked with related clades of this bacteria. The second study basically agrees with the first using this time linguistic phylogeny to trace the route of Austronesian speakers. Both studies claim that the Austronesian expansion began in Taiwan.

Opposing claims include an Austronesian expansion beginning in South China; and the two that I find most compatible with the evidence: an expansion from Indochina as espoused by Wilhelm Solheim; or from Sundaland or Insular Southeast Asia as brought forth by Stephen Oppenheimer. The datings also of the new study seem to recent when compared to the archaeological, genetic, and in my view also the linguistic evidence.

From other press releases, it appears that the authors are suggesting an initial expansion from Taiwan and then a secondary one from the Philippines. The second demographic movement might be linked with the divergence of Proto-Malayo-Polynesian, which if true I would find agreeable at least in terms of geography (but not chronology).

Paul Kekai Manansala

Science. 2009 Jan 23;323(5913):527-530.

The Peopling of the Pacific from a Bacterial Perspective.

Max-Planck-Institut für Infektionsbiologie, Department of Molecular Biology, Charitéplatz 1, 10117 Berlin, Germany.

Two prehistoric migrations peopled the Pacific. One reached New Guinea and Australia, and a second, more recent, migration extended through Melanesia and from there to the Polynesian islands. These migrations were accompanied by two distinct populations of the specific human pathogen Helicobacter pylori, called hpSahul and hspMaori, respectively. hpSahul split from Asian populations of H. pylori 31,000 to 37,000 years ago, in concordance with archaeological history. The hpSahul populations in New Guinea and Australia have diverged sufficiently to indicate that they have remained isolated for the past 23,000 to 32,000 years. The second human expansion from Taiwan 5000 years ago dispersed one of several subgroups of the Austronesian language family along with one of several hspMaori clades into Melanesia and Polynesia, where both language and parasite have continued to diverge.

Science. 2009 Jan 23;323(5913):479-483.

Language Phylogenies Reveal Expansion Pulses and Pauses in Pacific Settlement.

Department of Psychology, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.

Debates about human prehistory often center on the role that population expansions play in shaping biological and cultural diversity. Hypotheses on the origin of the Austronesian settlers of the Pacific are divided between a recent "pulse-pause" expansion from Taiwan and an older "slow-boat" diffusion from Wallacea. We used lexical data and Bayesian phylogenetic methods to construct a phylogeny of 400 languages. In agreement with the pulse-pause scenario, the language trees place the Austronesian origin in Taiwan approximately 5230 years ago and reveal a series of settlement pauses and expansion pulses linked to technological and social innovations. These results are robust to assumptions about the rooting and calibration of the trees and demonstrate the combined power of linguistic scholarship, database technologies, and computational phylogenetic methods for resolving questions about human prehistory.