The world’s earliest seafarers, who set out to colonize remote Pacific islands nearly 3,000 years ago, were a matrilocal society with communities organized around the female line, an analysis of ancient DNA shows.
The study, based on genetic sequencing of 164 ancient individuals from 2,800 to 300 years ago, suggests that some of the earliest inhabitants of Oceania’s islands had population structures in which women almost always remained in their communities after marriage, while men leave their mother’s community. to live with that of his wife. This pattern is strikingly different from the patrilocal societies that appear to have been the norm in ancient populations in Europe and Africa.
“The peopling of the Pacific Ocean has been a long-standing and important mystery because it was the last major expansion of humans into unoccupied areas,” said David Reich, a professor of genetics at Harvard Medical School who led the work.
“Today, traditional Pacific communities have both patrilocal and matrilocal population structures, and there has been debate about what was the usual practice in ancestral populations,” he said. “These results suggest that matrilocality was the rule among the earliest mariners.
50,000 years ago, populations of ancient humans arrived and spread across Australia, New Guinea and the Solomon Islands. But it wasn’t until 3,500 years ago that humans, probably living in present-day Taiwan, developed long-distance canoes and ventured out into the open ocean, arriving in remote Oceania. This extension includes the region called Micronesia—about 2,000 small islands north of the equator, including Guam, the Marshall Islands, the Caroline Islands, Palau, and the Northern Mariana Islands.
The latest findings, published in the journal Science, involved whole-genome analysis of 164 ancient individuals from five islands, dating from 2,800 to 300 years ago, and 112 modern individuals. When individual populations remain isolated over time—on islands, for example—their genomes drift apart. This effect was seen in ancient Micronesians, but genetic drift was significantly greater in mitochondrial DNA, a part of the genome that is passed down only through the female line. This strongly suggests that women did not move within communities as much as men.
“Women certainly moved to new islands, but when they did, they were part of joint movements of both women and men,” Reich said. “This pattern of leaving the community must have been almost unique to men.”
The work also revealed new evidence of migrations—again almost exclusively male—from mainland New Guinea that contributed Papuan ancestry to those living today on some Micronesian islands.
Dr Mark Dyble, an anthropologist at University College London who was not involved in the research, said matrilocal societies were “unusual but by no means unique”, with evidence of matrilocality in pre-industrial societies in the Amazon basin, central China and South India.
Matrilocality should not necessarily be equated with matriarchy, Dyble stressed. “Matrilocality creates an image of peaceful inter-island relations, with men leaving their island to marry and women staying there,” he said. “However… the same genetic makeup of the islands could probably be obtained by men taking over neighboring communities by force. This is probably still considered matrilocal residence, as the men disperse and the women remain on their home island. But on the ground it’s quite a different scenario.”
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