Humans are thought to have settled the remote tropical Pacific islands in two distinct migrations beginning about 3,330 years ago.
The first departed from today’s Philippines along the northern route, and the second departed from Taiwan and New Guinea along the southern route. About 1,000 years later, people reached the islands between these routes – which now form the Federated States of Micronesia.
But a new finding by Tufts sea-level researchers and colleagues suggests that the Micronesian islands may have been settled much earlier than expected, and that voyagers on both routes may have interacted.They reported their research in the journal Member of the National Academy of Sciences.
Andrew Kemp, an associate professor in the Department of Earth and Climate Sciences, was drawn to Micronesia to improve understanding of how climate change affects global sea level changes by gathering new data from the tropical Pacific Ocean, which is less well documented than in the North Atlantic.
With support from the National Science Foundation, the team collected mangrove sediment cores on the islands of Kosrae and Pohnpei in the Federated States of Micronesia.
While relative sea level—the height of land relative to the height of its nearby ocean—has declined over much of the tropical Pacific over the past 5,000 years, in Micronesia, radiocarbon dating shows a significant rise in relative sea level, It rose about 4.3 meters (14 feet) because the island was sinking.
Although the researchers can’t yet fully explain why the two islands are sinking so much faster than the rest of the Pacific Ocean, they can clearly see the results and their implications for understanding how people came to settle remote Oceania.
The team — which included Juliet Sefton, then a postdoctoral fellow at Tufts University and now an assistant lecturer at Monash University in Australia, and Mark McCoy, associate professor of anthropology at Southern Methodist University — were struck by the impact of relative sea levels on humans. Explain Nan Madol The massive ruins of the , a series of stone buildings built on islets separated by sea-filled canals off the coast of Pohnpei.
The ruins, now a United Nations World Heritage Site, have long been thought to be administrative or religious structures constructed around 1,000 years ago to house the island’s elite separately from the island’s main population.
But Kemp and his colleagues realized that long-term relative sea level rise meant that assumption was incorrect. When the buildings were built, they were on the island, not separated by water. According to McCoy, Nan Madol’s popular description as the “Venice of the Pacific” at the time of its construction may not be accurate.
This has researchers wondering when the islands actually became settled. Kemp points out that the voyagers who first came to the islands likely lived on the coastlines — which is why researchers look for archaeological evidence there, but haven’t seen older settlements there.
“We suggest that Pohnpei and Kosrae islands may not have been settled anomalously late, but were settled at about the same time as the other Pacific islands,” Sefton said. “People arrived and lived on the coast, but the sinking of the islands caused a relative rise in sea level, drowning out the oldest archaeological evidence. It may be underwater, but it has not yet been found – if ever found.”
If so, northern and southern migratory peoples may have interacted around the Micronesian volcanic islands of Kosrae, Pohnpei, Chuuk and Yap.
There was no previous evidence for this because researchers made false assumptions about when the islands were first inhabited, based on sea levels. McCoy noted that archaeologists “have been looking in the wrong places for years because we assumed relative sea levels were falling.”
“While we cannot prove that there is an interaction between these two pathways, we can make an argument that the data on migration in the Pacific today may be much less complete than one might think,” Kemp said.
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