NEW YORK (GenomeWeb News) – Genomic analysis is helping anthropologists move one step closer to resolving a long-held debate about the ancestry of populations in the Pacific islands.
Temple University anthropologist Jonathan Friedlaender and colleagues used whole genome analysis of autosomal markers to map Pacific geo-ancestry. Their findings, published online last night in PLoS Genetics, suggest Polynesian populations such as Maori and Samoans are more closely related to populations in and around Taiwan and East Asia than they are to populations in Melanesia — a region including New Guinea, the Bismarck Archipelago, and the Solomon Islands.
This supports the theory that Polynesians originated in East Asia and migrated through Melanesia relatively quickly. The genetic grouping also highlighted the extraordinary diversity of Melanesian populations. “What we were able to do was to greatly expand the sampling of the Pacific,” Friedlaender, the study’s lead author, told GenomeWeb Daily News. “It showed even greater diversity than we imagined.”
Friedlaender collected blood samples from almost 1,000 individuals within 41 Pacific populations over about a decade. The samples were subsequently analyzed at Wisconsin’s Marshfield Clinic. Using the HGDP-CEPH Human Genome Diversity Cell Line Panel, the researchers analyzed nearly 900 autosomal markers, including roughly 700 microsatellite regions and 200 insertion or deletion markers. The team used STRUCTURE software to cluster related individuals into sub-populations and groups within a larger population.
In contrast to previous studies by other groups which focused on single locus mitochondrial DNA or sequence information from the Y chromosome, the researchers focused on autosomal markers from throughout the genome for this study. Co-author James Weber, formerly of the Marshfield Clinic and now president of Prevention Genetics, told GenomeWeb Daily News that these unlinked markers were carefully selected and consistent with those used in previous geo-ancestry studies, which could potentially facilitate genetic ancestry analysis for populations throughout the world.
In an unpublished letter to Science obtained by GenomeWeb, Berkeley archeologist and historical anthropologist Patrick Kirch, a veteran Pacific researcher who was not involved in the study, called the results a “truly a major accomplishment in the field of Pacific anthropology.”
Kirch argues that the paper is not only consistent with archaeological and language comparison studies, but also “puts the true complexity of human genetic variation in Near Oceania (the New Guinea and Bismarck Archipelago part of Melanesia) into a larger picture.”
For years, anthropologists have argued about Polynesian ancestry. Conflicting hypotheses suggested Polynesians either originated in Taiwan, moving quickly through Melanesia with little interaction or, alternatively, that the group actually descended from Melanesians. This study supports the former hypothesis. Although there was some mixing between Polynesian and Melanesian populations, Friedlaender said, the genetics say Polynesians are not Melanesian descendants.
The work also supports the notion that Melanesian populations settled on the islands between 30,000 and 50,000 years ago, while Polynesians and other cultures originating in the West did not interact with the Melanesians before about 3,000 to 3,500 years ago. “They built up a very special set of genetic signatures in that time,” Friedlaender explains.
“From a genetic perspective,” Friedlaender says, “the whole notion that the Polynesians derived from Melanesians is no longer possible.”