New light has been shed on early human settlement of Remote Oceania - a region encompassing Fiji, Micronesia, New Caledonia, New Zealand, Polynesia, the Santa Cruz Islands, and Vanuatu.
Specifically, the evidence comes from new information about the water levels around the high islands of Micronesia. High islands, also called volcanic islands, usually sit anywhere between one and 50 meters above sea level. The term "high islands" serves to distinguish them from low islands which are formed from sedimentation or coral reefs.
Settlement of Remote Oceania began about 3,000 years ago, supposedly coinciding with falling sea levels across the equatorial Pacific Ocean. A new peer-reviewed study published in the Proceedings of the National Academy of Sciences (PNAS) explained that current archeological evidence suggests that the first human settlers of Pohnpei and Kosrae - the high islands of Micronesia - arrived approximately 1,000 years later than on other high islands.
However, the study continues to explain that the evidence is likely biased. Scientists reconstructed the sea levels on the two high islands using mangrove sediment and found that, rather than falling, the sea level rose by approximately 4.3 meters over the past 5,700 years. This likely washed away any coastal evidence of human settlement and skewed evidence toward a later arrival.
Mangrove sediment evidence
Mangroves are trees that grow in coastal saltwater or brackish water. As the sea level rises, organic carbon and sediments build up under the mangrove forests, creating deep, layered soil deposits.
Researchers took samples from the mangrove forests on Pohnpei and Kosrae and determined that the oldest sediment is approximately 5,700 years old. From there, they were able to calculate the degree to which the sea level has risen in the intervening millennia.
The study concluded that, because the sea level rose over time, there may be evidence of earlier human life on the islands that is submerged underwater. This also raises the question of where those humans may have come from, the west or the south.