Ancient DNA yields surprising findings about the world’s earliest seafarers

New genetic research from remote Pacific islands provides new insights into the ancestry and culture of the world’s earliest seafarers, including the family structure, social customs and ancestral populations of the people who live there today.

The work, described in the magazine Sciencereveals five previously undocumented migrations to a subregion of this area and suggests that about 2,500 to 3,500 years ago, the early inhabitants of these Pacific islands—including Guam in the northern region and Vanuatu in the southwest—had matrilocal population structures where women were almost always stayed in their community after marriage, while men were more likely to move out of their mother’s community to live with their wives’.

The practice is different from that of patrilocal societies where women overwhelm those who leave their own communities. These findings support the idea that the world’s earliest seafarers were organized through female genders.

The results come from a genome-wide analysis of 164 ancient individuals from 2,800 to 300 years ago, as well as 112 modern individuals. It was published by a team of researchers led by Harvard geneticists David Reich and Yue-Chen Liu, Ron Pinhasi of the University of Vienna and Rosalind Hunter-Anderson, an independent researcher working in Albuqueque, New Mexico.

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

The genetic analysis compared early seafarers from Guam, Vanuatu and Tonga — who lived about 2,500 to 3,000 years ago — and revealed that their mitochondrial DNA sequences, which humans inherit only from their biological mothers, differed almost completely, while being much more different from the rest of their DNA. The only way this could happen is if migrants who left their communities to marry into new communities were almost always male.

“Women certainly moved to new islands, but when they did, they were part of joint movements of both women and men,” explains Reich. “This pattern of community abandonment must have been almost unique for males to explain why genetic differentiation is so much higher in mitochondrial DNA than in the rest of the genome.”

The new study from an interdisciplinary team of geneticists and archaeologists fivefold the body of ancient DNA data from the vast Pacific Ocean called Remote Oceania, the last habitable place on Earth to be populated. It also offers surprising insights into the extraordinarily complex populations of one of the most important sub-regions of remote Oceania.

Humans arrived and spread through Australia, New Guinea, the Bismarck Archipelago, and the Solomon Islands beginning 50,000 years ago, but it was not until 3,500 years ago that humans first began living in remote Oceania following the development of the technology to to sting open water in unique long-distance canoes.

This expansion included the region called Micronesia: about two thousand small islands north of the equator, including Guam, the Marshall Islands, the Caroline Islands, Palau, and the Northern Mariana Islands.

It has long been a mystery what routes people took to arrive in the region. The disclosure of five migratory flows to Micronesia helps shed light on this mystery and the origins of the people there today.

“These migrations that we’re documenting with ancient DNA are the key events shaping the unique history of this region,” said Liu, a postdoctoral researcher in Reich’s lab and the study’s lead author. “Some of the findings were very surprising.”

Of the five migrations detected, three were from East Asia, one from Polynesia, and a Papuan lineage from the northern fringe of mainland New Guinea. New Guinea’s native ancestors were a big surprise, as another stream of this migration — one from New Britain, an archipelago east of New Guinea — was the source of the Papuan lineage in the southwestern Pacific and in Central Micronesia.

The researchers also found that the current indigenous peoples of the Marianas in Micronesia, including Guam and Saipan, derive almost all of their pre-European ancestry from two of the East Asian migrations the researchers discovered. It makes them the “only people of the open Pacific who have no ancestry from the New Guinea region,” Liu said.

The researchers consulted several indigenous communities in Micronesia for the study. This is the fourth publication of original ancient DNA data from remote islands in the Pacific Ocean by Reich’s group.

“It’s important that when we’re doing old DNA work, we don’t just write a paper on a region’s population history and then move on,” Reich said. “Each article raises as many new questions as it answers, and this requires long-term commitment to follow up on the initial findings. In the Pacific Islands, there are so many open questions, so many surprises yet to be discovered.”