Discussion
In summary, the admixture time analysis of two different genome-wide datasets provides compelling evidence that people of Asian ancestry began moving through East Indonesia about 4,000 y ago from west to east and admixed with resident groups of Papuan ancestry. Furthermore, this scenario is in excellent agreement with linguistic, archaeological, and genetic evidence for a pre-Austronesian presence of Papuans in East Indonesia (4, 25, 26) and an eastward spread of Austronesian-speaking farmers across East Indonesia (9, 21). Our results showed that the major direction of Asian gene flow has been from west to east across East Indonesia, but they do not rule out other proposed migration events that would have had a lesser genetic impact. Our analyses, thus, refute suggestions that the Asian ancestry observed in Indonesia largely predates the Austronesian expansion (2, 27), or that the Austronesian expansion was not accompanied by large-scale population movement (4). To be sure, other migrations (both before and after the Austronesian expansion) have undoubtedly left a genetic legacy in Indonesia. However, our analyses of genome-wide data do indicate that there was a strong and significant genetic impact associated with the Austronesian expansion in Indonesia, just as similar analyses have pointed to a genetic impact associated with the Austronesian expansion through Near and Remote Oceania (24, 28). Given that admixture among human populations (and between modern and archaic humans) is increasingly being recognized as a significant aspect of modern human biology (29), estimates of the time of admixture should provide important insights into the history of our species.
Genetic dating indicates that the Asian–Papuan admixture through Eastern Indonesia corresponds to the Austronesian expansion | PNAS
