A recent study has analysed the first ancient human genomes from Papua New Guinea, revealing that some early populations in the region were entirely genetically isolated from their neighbours. This indicates that there was minimal intermarriage over various periods. Papua New Guinea, the world's second-largest island after Greenland, along with its surrounding islands, played a crucial role as launching points for early maritime expeditions into the broader Pacific. These journeys eventually led to the settlement of some of the last islands on Earth to be permanently inhabited. Despite this significance, much of the island's ancient genetic history has remained largely unexplored until now.
In a recent study, researchers examined ancient DNA extracted from the bones and teeth of 42 individuals who lived up to 2,600 years ago in Papua New Guinea, which occupies the eastern half of the island of New Guinea, as well as in the nearby Bismarck Archipelago, located northeast of the main island.
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"This has been a long time in the making," said Kathrin Nägele, an archaeogeneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, in an interview with Live Science. "DNA preservation in tropical environments is extremely difficult."
Previous studies indicated that New Guinea and its surrounding areas were first inhabited over 50,000 years ago. Much later, around 3,300 years ago, new seafaring groups with Asian ancestry arrived in the Bismarck Archipelago. This group, known as the Lapita culture, is famous for its elaborate pottery and agricultural practices, which included raising pigs, dogs, and chickens, as well as cultivating coconuts, bananas, yams, and various types of breadfruit.
The recent discoveries unexpectedly showed that the earliest known inhabitants of the Bismarck Archipelago and the Lapita people did not genetically intermix for centuries. However, one individual analysed indicated that intermixing occurred approximately 2,100 years ago.
"Even though both groups coexisted, it appears they did not mix for a significant period, which is quite unusual in human interactions," said Rebecca Kinaston, an anthropologist and co-lead author of the study, as well as the director of BioArch South, an archaeology and forensic anthropology consultancy in New Zealand.
These findings provide insights into the ancestry of remote Oceanic islands like Samoa, Tonga, and Vanuatu. They corroborate earlier research indicating that Papuans and the Lapita people arrived independently on these distant islands and intermarried there, rather than mixing first in New Guinea and nearby islands before travelling to these remote locations.
"It suggests that the Papuans had their own impressive seafaring abilities," Nägele noted. "The seafaring hunter-gatherers of Papua New Guinea have likely been underestimated, much like hunter-gatherer societies are often undervalued worldwide."
A remarkable finding emerged when scientists examined two communities that lived along the south coast of Papua New Guinea between 150 and 500 years ago. "Despite being only a few kilometres apart, these two communities were surprisingly genetically distinct," said Nägele. "To trace their direct family connections, we had to go back six generations to identify a common ancestor, indicating that for six generations, the two groups did not intermix, even with no geological barriers separating them."
Both communities exhibited a blend of Papuan-related and Southeast Asian ancestries. The group interred at the Eriama site displayed a higher proportion of Papuan-related ancestry, while the Nebira site had a greater representation of Asian ancestry.
What caused these groups to cease their interactions? One potential explanation is the difficult climatic conditions in New Guinea between 1,200 and 500 years ago, which may have led to more frequent El Niño events, including significant droughts.
"Settlements were deserted, possibly as people moved to more viable, unknown locations," Nägele exexplained "We believe that wherever they went, they began to participate in new trade networks. Nebira seemed to connect more with coastal communities, while Eriama interacted more with inland groups from the highlands. This could have resulted in the development of distinct identities, varied cuisines, and other differences that contributed to cultural diversification."
In the future, the researchers aim to gather older genetic data and samples from the highlands of New Guinea, as well as from the earliest Asian-related populations to reach the island's coast. "Papua New Guinea is incredibly diverse in many ways, and we have only begun to explore the rich history of the world's second-largest island," Nägele stated.
