Scientists have a new theory on timing for human settlement of some parts of tropical Pacific

The islands of the tropical Pacific Ocean are believed to have been populated by humans around 3,330 years ago.

The first followed a northern route out of the Philippines while the second followed a southern route. The Federated States of Micronesia are made up of the islands between these routes.

A new finding by a sea level researcher and his colleagues suggests that the islands in Micronesia may have been settled earlier than thought, and that voyagers on the two routes may have interacted with one another. The researchers have reported their work.

Andrew Kemp, an associate professor in the Department of Earth and Climate Sciences, was drawn to Micronesia to improve understanding of how climate change impacts global sea level change by collecting new data from the tropical Pacific Ocean.

There are two islands in the Federated States of Micronesia.

Over the past 5,000 years, the relative sea level has fallen across much of the tropical Pacific, but it has risen in some places.

Although the researchers can't explain why the two islands are subsiding so fast, they can clearly see how people came to populate remote Oceania.

The implications of relative sea level for interpreting the monumental ruins of Nan Madol were struck by the team.

The ruins are thought to have been built about 1000 years ago for the island's elite to live apart from the rest of the island.

Kemp and his colleagues realized that the presumption was wrong. The structures were on the island and not in the water. The "Venice of the Pacific" may have been incorrect when it was constructed.

It made the researchers think about when these islands were actually settled. The people who first came to the islands would have lived at the coastline. Researchers look for archaeological evidence but have not seen it for older people.

The other islands in the Pacific were settled at the same time as Pohnpei and Kosrae. The oldest archeological evidence was submerged due to the sea level rise caused by the island subsidence. If it will ever be found, it is likely underwater.

It is possible that people on the northern and southern migrations interacted with one another around the islands of Micronesia.

Researchers were wrong in their assumptions about when the islands were first inhabited. Archaeologists have been looking in the wrong place for a long time because they assumed that the sea level was going down.

"Although we can't prove that there was interaction between these two pathways, we can present an argument that says the data that exists now about migration in the Pacific is probably more incomplete than it is thought to be," says Kemp.

There is more information about the implications of sea-level rise for the peopling of remote islands. www.pnas.org/

Journal information: Proceedings of the National Academy of Sciences