| Abstract: |
This thesis describes an investigation of the evolutionary origins and affinities of Pacific populations based on analyses of mitochondrial and Y chromosome DNA. A common framework of Pacific prehistory posits that all populations trace their origins to two distinct diasporas. The first, an ancient migration ultimately from Africa, arrived in Sahul, (the Pleistocene continent of Australia, New Guinea and Tasmania) and Melanesia approximately 60,000 years ago. This was followed by a recent Austronesian migration, beginning 6,000 years ago from Taiwan and Southern China, into Island Southeast Asia, coastal New Guinea, and the island expanses of Micronesia and Polynesia. These hypotheses were tested using phylogenetic, multidimensional scaling, population structure, and demographic analyses of data generated from the mitochondrial DNA control-region and four short-tandem- repeat (STR) loci on the Y chromosome in Pacific populations. A novel multiplex amplification procedure was developed for the STRs. The results from these studies have several implications for the two-episode migration model of the Pacific. The first study uncovered a genetic trail of a distinctive Polynesian motif from Southeast Asia to Polynesia and dated its origin and expansion and, by extension, the origin of Polynesian populations. These results do not support a putative Melanesian origin for Polynesians, but rather they support Southeast Asia as the clear source of the vast majority of maternal Polynesian genes. The second and third studies of the peopling of Sahul based on maternal and paternal DNA revealed some unprecedented patterns. Both studies do not support the widely assumed common origin model for the peopling of Sahul. Although multiple loci are required for robust inferences about population history, the mitochondrial DNA variation suggests substantial genetic divergence between New Guinean highlanders and all other populations, while the Australian Aboriginal populations have affinities with populations from the subcontinent of India. The Y chromosome STR study uncovered Australian Aboriginal- specific DYS390 alleles, and provided evidence for a violation of the stepwise-mutation-model. Female and male patterns of DNA variation are distinct in the Pacific
women from Papua New Guinea have divergent mitochondrial lineages, while men from Australia have a high frequency of population-specific lineages on the Y chromosome.
|
