On the trail of the early inhabitants of Micronesia: By analyzing ancient DNA, researchers have gained clues to the history of settlement of this island world in the western Pacific and to a special gender rule among the early seafarers. According to this, people came to the South Seas region from different Southeast Asian islands in five waves of migration from around 3500 years ago. In addition, there were genetic traces of a so-called matrilocality: men looked for partners abroad and then settled in the women’s community.
According to the current state of research, modern humans emerged in Africa, then spread throughout the world and later human history was repeatedly shaped by further waves of migration. Researchers are now increasingly gaining insights into these developments through modern genetics: By comparing the genome of populations and by analyzing DNA residues from bone finds, conclusions can be drawn about the history of population developments. The focus of the current study was a region that was settled rather late: the island world of Micronesia.
Five migration waves are emerging
According to previous information, humans first reached Australia, New Guinea, the Bismarck Archipelago and the Solomon Islands around 50,000 years ago. But it wasn’t until 3,500 years ago that they ventured into more distant Oceania after developing the technology to cross open waters in long-distance canoes. This expansion eventually included the Micronesia region. These are about two thousand small islands in the western Pacific Ocean north of the equator. However, details of the settlement history of this island world have so far remained in the dark.
To gain insight, the researchers, led by Yue-Chen Liu of Harvard Medical School in Boston, examined genomes from 164 human remains from various archaeological sites in the region. They date from 2800 to 500 years ago. They also analyzed DNA from 112 modern humans from the same area. As the team reports, their results now show five different waves of migration to Micronesia. Three of these came from East Asia, one from Polynesia, and one Papuan lineage apparently hailed from the northern edge of mainland New Guinea. “These migrations, which we were able to document using ancient DNA, are the key events that shaped the unique history of this region,” says Liu.
The men went to the women
Of particular interest, however, is a pattern in the genetic findings that even allows conclusions to be drawn about the cultural behavior of the region’s early inhabitants. Basically, the researchers found that female mitochondrial DNA, which is only passed on from mothers, differed greatly between insular communities. But it was strikingly similar within communities on the many Pacific islands. According to the researchers, this can be explained by the cultural practice of so-called matrilocality: women stayed in their communities after marriage, while men more often left their mothers’ communities to live in their wives’. This practice is thus different from that of patrilocal societies, where it is predominantly women who leave their own communities. The researchers say these findings support the notion that the world’s earliest seafarers were organized along female lines.
“It’s an unexpected gift to be able to learn about cultural patterns from genetic data,” says senior author David Reich of Harvard Medical School. “Today, both patrilocal and matrilocal population structures exist in traditional Pacific communities, and there has therefore been debate as to what might have been common practice in the original populations. Our results now suggest that matrilocality was the rule among the earliest seafarers,” the scientist sums up.
Source: Harvard University, professional article: Science, doi: 10.1126/science.abm6536