Genetic dating indicates that the Asian-Papuan admixture through Eastern Indonesia corresponds to the Austronesian expansion

Abstract

he spread of Austronesian-speaking peoples ultimately extended well over halfway around the world from Madagascar in the west to Easter Island in the east. This process is often termed the Austronesian expansion, which represents a complex demographic process of interaction between migrating Neolithic farmers and indigenous Mesolithic hunter–gatherer communities, a frequent phenomenon in world prehistory. However, our knowledge about the historical origin and spread of Austronesian-speaking peoples has been overwhelmingly from linguistic, archaeological, and anthropological studies (1). The genetic impact of the Austronesian expansion has been contested, with some studies claiming that the genetic ancestry of Island Southeast Asia mostly reflects pre-Austronesian migrations (2, 3) and that the Austronesian expansion did not involve large-scale population movements (4). Eastern Indonesia (consisting of the Nusa Tenggaras and Moluccas) (Figs. 1 and 2) provides a unique opportunity to investigate the extent to which the genetic ancestry in this region reflects Austronesian or pre-Austronesian migration(s). Both Asian and Papuan (related to New Guinea) genetic ancestry is evident in East Indonesia based on mtDNA and Y-chromosome studies (5, 6) as well as a recent study (7) of multiple autosomal and X-chromosomal SNPs, and there is a decline in Asian ancestry (and corresponding increase in Papuan ancestry) going from west to east. Because the time of the entry of the Austronesians into Indonesia has been dated by both archaeological and linguistic evidence to about 4,000 y ago (8, 9), estimating the time of the admixture between Asian and Papuan ancestry in East Indonesian groups could, therefore, distinguish between a preAustronesian vs. Austronesian explanation for the Asian ances4574–4579 | PNAS | March 20, 2012 | vol. 109 | no. 12