Genetic insights on the human colonization of Indonesia

Indonesia, a vast archipelago nation and home to a wide range of cultural, linguistic and genetic diversity, has been a navel of intercultural and interregional interaction between the Asian and the Pacific worlds since prehistoric times. By analyzing the genetic profile of Indonesian people across the archipelago, this dissertation aims to elucidate the colonization history of Indonesia and to assess the effect of social practices on the Indonesian gene pool. Genetic diversity has revealed the complex settlement history of the Indonesian archipelago, starting from the initial colonization of Indonesia ∼50 kya, multiple migrations by hunter-gatherers from mainland Asia during the Paleolithic era, followed by a major Neolithic expansion of Austronesian-speaking farmers from a putative homeland of Taiwan, and historic era migrations that involved several foreign invasions via trading and the spread of major religions.;The survival of older lineages in western and eastern Indonesia showed that these later expansions into the archipelago did not replace the gene pool of the previous inhabitants. Although most Indonesian communities today practice patrilocality, which is supported by genetic diversity and population structure analyses, matrilineal descent systems are thought to have dominated ancestral Austronesian societies. Preserving a rich Austronesian cultural heritage, such as matrilocal marriage practices, has particularly affected the genetic diversity and population structure of Timor. The dominance of Asian female lineages is apparent on the X chromosome compared to the autosomes, suggesting that female migrants played a leading role during the period of Asian immigration into Timor. Matrilocality may have been a driving force behind this admixture bias during the Austronesian expansion. This finding provides support for an Austronesian 'house society' model in which the Austronesian expansion led to the dispersal of matrilocal societies with small numbers of neighboring non-Austronesian males marrying into Austronesian matrilocal, matrilineal houses. This study has revealed that the colonization history of Indonesia does not seem to comprise merely a Melanesian substratum with a single expansion of Austronesian speakers, yet rather involves multiple waves of human migration, coupled with an extensive admixture process.