by Jolie Liston

A new DNA study spearheaded by archaeologists Rosalind Hunter-Anderson and Joanne Eakin and just published in the prestigious journal Science provides surprising insights into the ancestry and culture of Micronesia’s earliest transoceanic seafarers.

Humans began populating Near Oceania–Australia, New Guinea, the Bismarck Archipelago, and the Solomon Islands–about 47,000 years ago. It wasn’t until about 3,500 years ago, after lower sea levels enlarged islands throughout Oceania and people developed the technology to cross open water in long-distance canoes, that people began living in Remote Oceania–Micronesia, eastern Melanesia, and Polynesia. Micronesia was populated earlier than Remote Oceania’s other island groups but where did the colonizers come from? Why are the island cultures and languages different from each other as well as similar? Did groups migrating later replace the islands’ previous populations and cultures?

Some of these mysteries are being answered by a team of archaeologists, osteologists, cultural practitioners, and geneticists who conducted ancient DNA analysis on 112 modern individuals and 164 ancient individuals who lived in Micronesia as early as 2,800 years ago. Ancient DNA samples were collected largely from Guam and Saipan, with a few from Pohnpei, while modern DNA samples came from Guam, Chuuk, Pohnpei, and Palau. The collaboration included scientists from the Universities of Guam, Harvard, Vienna, and Hawaii, as well as local agency heads and community members.

The study identified five streams of migration into the vast region of Micronesia: three from the islands of Southeast Asia, one from Polynesia, and one from the northern edge of mainland New Guinea. The modern CHamoru of the Mariana Islands derive nearly all their ancient ancestry from two Island Southeast Asia migrations, most likely originating in eastern Indonesia. CHamoru are hence the only genetically analyzed indigenous people from Remote Oceania without Papuan ancestry. ‘Papuan’ refers to those with primary ancestry from New Guinea, the Bismarck Archipelago, and the Solomon Islands. These findings challenge older models based on language similarities and comparable pottery designs that claim CHamoru ancestral populations are from the northern Philippines. No comparative ancient DNA is available from the Philippines, but samples are being sought.

Analysis of modern DNA from 19 Palauans revealed Papuan ancestry from northern mainland New Guinea. These mostly male migrants arrived on Palau’s shores about 2,200 to 2,500 years ago. They encountered people already living on Palau whose genetic lineages originated in Island Southeast Asia, lineages first identified through ancient DNA research by archaeologist Jessica Stone and confirmed in this new study. A later stream of migration originating in New Britain in the Bismarck Archipelago brought the Papuan ancestry found in central Micronesia (Chuuk, Pohnpei, Kosrae) and in the southwest Pacific.

Genome-wide analysis also allows for the identification of family groups to reveal cultural practices. On ancient Guam and Saipan, the data shows there was a tendency for individuals closely related to each other through their mothers to be buried close together. Combined with evidence from mitochondrial DNA (mDNA), which is only inherited from biological mothers, there is strong evidence that the Marianas’ earliest inhabitants (about 3,000 to 3,500 years ago) were matrilocal. In matrilocal societies, women typically remain in their communities after marriage while men move to join their wives. As long suggested, Micronesia’s early seafarers originated from cultures organized through female lineages.

Another significant finding in the new research is that distinct changes in physical appearance and customs through time are not necessarily a result of new waves of migrations. Living 1,500 years apart and culturally, socially, and physically different, the people of the Mariana Island’s Unai Period and Latte Period share the same maternally inherited lineages. Furthermore, the genetic link shows the early populations are indeed the ancestors of CHamoru people living today, proof of genetic continuity across some 2,500 years.

The current study has limited Palau information because of the lack of ancient skeletal material sampled from here. In collaboration with the Palau Bureau of Cultural and Historic Preservation, a goal of the next phase of this DNA research is to analyze early burials previously collected by archaeologists in Rock Island, Koror, and Babeldaob burial sites. This research can reveal new insights into the complex questions of the geographic origins of Palauans, timing of migrations into Palau, ancient family structure and social customs, and the ancestral relationship of Palauans with other Micronesians.

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