Settlers first arrived in East Polynesia around 200 years earlier than previously thought, according to new research.
Analysis of core samples of mud taken from Lake Te Roto on the tiny island of Atiu, in the southern group of the Cook Islands, suggests the arrival of people around 900 CE.
And when combined with the study of sediments collected in Samoa and Vanuatu, it points to climate change as the motivation behind the migration and the subsequent spread of settlements.
The research involved geographers, archaeologists and geochemists from the UK, New Zealand and the US, working with local islanders. The findings are published in the journal Proceedings of the National Academy of Sciences.
“The ancestors of the Polynesians, the Lapita people, migrated east into the Pacific Ocean as far as Fiji, Tonga and Samoa, reaching them around 2800 years ago, but for almost 1500 years humans failed to migrate any further into the Pacific,” says lead researcher David Sear from the University of Southampton, UK.
“Our research gives us a much more accurate timescale of when people first arrived in the region and helps answer some key questions about why they made their hazardous journey east.”
The lake sediments were subjected to a range of analyses, including new techniques for reconstructing precipitation and detecting the presence of mammalian faeces. Both were significant.
Apart from fruit bats, there were no mammals in the southern Cook Islands before humans settled there, the researchers say, so evidence of mammal faeces alongside evidence for landscape disturbance and burning was a clear sign of the arrival of people.
And rainfall data revealed a major change in the climate of the South Pacific region, with the main rainbands that bring water to the archipelagos of Vanuatu, Samoa, Tonga and Fiji migrating north. The result was the driest period in the past 2000 years.
This led Sear and colleagues to conclude that, alongside growing populations, water stress drove decisions to make dangerous voyages, aided by changes in winds that enabled easterly sailing.
Soon after the arrival of people to Atiu, the climate changed again. Rain returned to the eastern Pacific, supporting a rapid settlement of the remaining islands of Polynesia over the next 200 years.
In their paper, the researchers say that the distances between settled islands in the west and those of the vast East Polynesian region suggest that provisioning stations, especially those with fresh water, may have been crucial in the eastward expansion process.
“The Lake Te Roto… record suggests populations from West Polynesia began exploratory probes along the margins of East Polynesia into the SCIs [Southern Cook Islands] and possibly other proximate archipelagos such as the Societies, well before full-fledged colonising expeditions were launched,” they write.
Nick Carne is editor of Cosmos digital and editorial manager for The Royal Institution of Australia.
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