The Genetic Structure of Pacific Islanders

Jonathan S Friedlaender,Floyd A Reed,James L Weber,Françoise R Friedlaender,George Koki,Kenneth K Kidd,Jason A Hodgson,Geoffrey K Chambers,D Andrew Merriwether,Rodney A Lea,Jun-Hun Loo,Judith R Kidd

doi:10.1371/journal.pgen.0040019

Abstract

Human genetic diversity in the Pacific has not been adequately sampled, particularly in Melanesia. As a result, population relationships there have been open to debate. A genome scan of autosomal markers (687 microsatellites and 203 insertions/deletions) on 952 individuals from 41 Pacific populations now provides the basis for understanding the remarkable nature of Melanesian variation, and for a more accurate comparison of these Pacific populations with previously studied groups from other regions. It also shows how textured human population variation can be in particular circumstances. Genetic diversity within individual Pacific populations is shown to be very low, while differentiation among Melanesian groups is high. Melanesian differentiation varies not only between islands, but also by island size and topographical complexity. The greatest distinctions are among the isolated groups in large island interiors, which are also the most internally homogeneous. The pattern loosely tracks language distinctions. Papuan-speaking groups are the most differentiated, and Austronesian or Oceanic-speaking groups, which tend to live along the coastlines, are more intermixed. A small “Austronesian” genetic signature (always <20%) was detected in less than half the Melanesian groups that speak Austronesian languages, and is entirely lacking in Papuan-speaking groups. Although the Polynesians are also distinctive, they tend to cluster with Micronesians, Taiwan Aborigines, and East Asians, and not Melanesians. These findings contribute to a resolution to the debates over Polynesian origins and their past interactions with Melanesians. With regard to genetics, the earlier studies had heavily relied on the evidence from single locus mitochondrial DNA or Y chromosome variation. Neither of these provided an unequivocal signal of phylogenetic relations or population intermixture proportions in the Pacific. Our analysis indicates the ancestors of Polynesians moved through Melanesia relatively rapidly and only intermixed to a very modest degree with the indigenous populations there.

Highlights

The populations in New Guinea and the islands immediately to the east are well-known for their great diversity in cultures, languages, and genetics, which by a number of measures is unsurpassed for a region of this size [1]
Nettle has argued that in ecologically rich tropical regions such as Near Oceania, small populations became self-sufficient, which in turn encouraged isolation and discouraged exchange [44,45], causing the development of extreme diversity among populations in both language and genetics. We suggest this was the underlying cause of the short marital migration distances among inland groups in Near Oceania, which in turn was responsible for the low population heterozygosities and resulting large genetic distinctions among groups [42]
2) How does the genetic diversity of Near Oceanic populations compare with groups in other regions? The within-group diversity in Melanesian populations is consistently very low, which acts to exaggerate the considerable among-group distinctions there

Summary

Introduction

The populations in New Guinea and the islands immediately to the east (the Bismarck and Solomons archipelagos) are well-known for their great diversity in cultures, languages, and genetics, which by a number of measures is unsurpassed for a region of this size [1]. This area is referred to as Near Oceania, as opposed to the islands farther out in the Pacific, known as Remote Oceania [2] (see Figure 1). There is evidence of sporadic, modest contact between New Guinea and the Bismarcks from 22,000 YBP, and with Bougainville/Buka in the Solomons only from ;3,300 years ago [3,7]

Results

Discussion

Conclusion