Saturday, October 1, 2022

Earliest seafarers had matrilocal society in Pacific Islands

The world’s earliest seafarers, who arrived in the Pacific Islands 2,500 to 3,500 years ago, lived in a matrilocal society organised through female lineages, a study suggests.

The analysis, from an international team of geneticists and archaeologists, compared DNA from the remains of early seafarers from Guam, Vanuatu, and Tonga. Their mitochondrial DNA, which people can only inherit from their mother, differed almost completely while the rest of their DNA was much more similar.

The researchers said the only way this could have happened was if they had matrilocal population structures where women almost always remained in their communities after marriage while men moved out to live with those of their wives. They said their findings, which are published in the journal Science, supported the idea that the seafarers were organised through female lineages.

David Reich, a professor in Harvard’s Department of Human Evolutionary Biology and at Harvard Medical School, said: “It’s an unexpected gift to be able to learn about cultural patterns from genetic data. Today, traditional communities in the Pacific have both patrilocal and matrilocal population structures and there was a debate about what the common practice was in the ancestral populations. These results suggest that in the earliest seafarers, matrilocality was the rule.”

The study also indicates that the inhabitants of the subregion of Micronesia derive their ancestry from at least five different streams of migration.

It’s an unexpected gift to be able to learn about cultural patterns from genetic data.

David Reich

Humans spread through Australia, New Guinea, the Bismarck Archipelago and the Solomon Islands from about 50,000 years ago. However, it was not until after 3,500 years ago that they began living in Remote Oceania after developing the technology to cross open water in long-distance canoes.

This expansion included the 2,000 or so islands of Micronesia including Guam, the Marshall Islands, the Caroline Islands, Palau, and the Northern Mariana Islands. There has long been a mystery around the routes that people took to arrive in the last habitable region to be peopled.

Of five migrations the researchers identified from the DNA, the three earliest were of people with origins in East Asia, one was from Polynesia, and one from the north of mainland New Guinea. The migrants of East Asian origin, the earliest seafarers, were related to prehistoric individuals from southeast China and Taiwan and to the ancestors of some groups in the Philippines.

This indigenous Papuan ancestry from New Guinea was a surprise as a different stream of Papuan migration — from New Britain, an island chain to the east of New Guinea — was the source of the Papuan ancestry in the southwest Pacific.

Yue-Chen Liu, a post-doctoral fellow in Reich’s laboratory and the study’s lead author, said: “These migrations we document with ancient DNA are the key events shaping this region’s unique history. Some of the findings were very surprising.”

The researchers also found that present-day indigenous people of the Mariana Islands in Micronesia, including Guam and Saipan, derive almost all their pre-European-contact ancestry from two of the East Asian migrations they detected. It makes them the “only people of the open Pacific who lack ancestry from the New Guinea region,” Liu said.

In their paper, they concluded that, given the diversity of ancestral origins they identified within the subregion of Micronesia, the term “Micronesian” should be used as a geographic label without implying a specific biological profile.

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