How accurate and robust are the phylogenetic estimates of Austronesian language relationships?

Simon J Greenhill,Alexei J Drummond,Russell D Gray,Dale J Hedges

doi:10.1371/journal.pone.0009573

Abstract

We recently used computational phylogenetic methods on lexical data to test between two scenarios for the peopling of the Pacific. Our analyses of lexical data supported a pulse-pause scenario of Pacific settlement in which the Austronesian speakers originated in Taiwan around 5,200 years ago and rapidly spread through the Pacific in a series of expansion pulses and settlement pauses. We claimed that there was high congruence between traditional language subgroups and those observed in the language phylogenies, and that the estimated age of the Austronesian expansion at 5,200 years ago was consistent with the archaeological evidence. However, the congruence between the language phylogenies and the evidence from historical linguistics was not quantitatively assessed using tree comparison metrics. The robustness of the divergence time estimates to different calibration points was also not investigated exhaustively. Here we address these limitations by using a systematic tree comparison metric to calculate the similarity between the Bayesian phylogenetic trees and the subgroups proposed by historical linguistics, and by re-estimating the age of the Austronesian expansion using only the most robust calibrations. The results show that the Austronesian language phylogenies are highly congruent with the traditional subgroupings, and the date estimates are robust even when calculated using a restricted set of historical calibrations.

Highlights

The past few years have seen a number of high-profile applications of Bayesian phylogenetic methods to lexical data [1,2,3] that have been very controversial [4]
The key topics of contention have been how accurate phylogenetic methods are at recovering linguistic history and how congruent the results are with the traditional linguistic comparative method
The first hypothesis argues for an origin in Taiwan around 5,500 years Before Present (BP), followed by a ‘‘pulse and pause’’ style expansion through the Pacific into the Philippines and Island South-East Asia, along the coast of New Guinea and into Oceania [5,6,7,8]

Summary

Introduction

The past few years have seen a number of high-profile applications of Bayesian phylogenetic methods to lexical data [1,2,3] that have been very controversial [4]. The first hypothesis argues for an origin in Taiwan around 5,500 years Before Present (BP), followed by a ‘‘pulse and pause’’ style expansion through the Pacific into the Philippines and Island South-East Asia, along the coast of New Guinea and into Oceania [5,6,7,8]. The second ‘‘slow boat’’ hypothesis argues for a much older origin in Island South-East Asia around 13,000– 17,000 BP followed by a two-pronged expansion flowing north into Taiwan, and east into Oceania [9,10,11]

Methods

Results

Discussion

Conclusion