The 24 major island groups of the Pacific Ocean were settled by early Austronesians between 3,500 and 900 years ago, but little is known about how these isolated islands were colonized. Now, researchers have used epidemiological modeling to devise some compelling new ideas about how it was done.

Above: A map of the Pacific showing the estimated number of years ago various island groups were settled. The compass shows the direction of prevailing easterly-southeasterly winds and the directions for safer or more dangerous journeys. (Caption and image credit: Adrian Bell, University of Utah)

By adapting a model of how diseases spread among animals and humans, researchers led by University of Utah anthropologist Adrian Bell were able to create a simulation of ocean migrants “infecting” uninhabited islands. The researchers keyed in a wide number of variables, including pre-existing archaeological evidence of settlements, inferred levels of social hierarchy, island size, distances between islands, and prevailing wind directions. This resulting simulation provided Bell and his colleagues with a hypothetical timeline of Oceania colonization. The researchers draw several interesting conclusions from this timeline, in the latest issue of the journal American Antiquity.

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A canoeist paddles between the islands of Vava’u, Tonga (Credit: Adrian Bell, University of Utah)

First, the Lapita people didn’t expand outward like ripples in a pond; rather, their advance was dictated by an island’s visibility, i.e. its height, width, and distance. Thus, volcanic islands, with their large “angle of target,” were likely spotted and settled first.

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Second, these early settlers may have utilized a “risk minimizing” strategy in which they traveled directly into prevailing winds. This might seem counterintuitive, but as noted in the study: “[H]eading into the prevailing wind on outward, exploratory journeys, [allowed] for safer return [with the wind] from failed searches.”

Thirdly, the study could neither confirm nor deny the idea that migrants were pushed away by hierarchical social structures. The authors admit that more research is necessary. And lastly, the researchers don’t believe that the quality of habitats played a role. As Bell noted in a statement: “Crossing and exploring was the driving force rather than skipping an island and looking for a better island.”

Fascinating stuff! The authors conclude by saying:

We show how decades of thinking on colonization strategies can be brought together and assessed in one statistical framework, providing us with greater interpretive power to understand a fundamental feature of our past.

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An ocean of stars: UGC 2683 (NASA/ESA/Hubble)

On a related note, this technique could conceivably used to estimate how extraterrestrial intelligences might colonize the galaxy; instead of islands, astrobiologists could chart how colonization waves move between stars. Interestingly, one of the key findings of the Bell paper is that distance didn’t matter in the founding of early Pacific societies. Maybe a similar inference can be made for interstellar explorers.

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Read the entire study at American Antiquity: “Driving Factors in the Colonization of Oceania: Developing Island-Level Statistical Models to Test Competing Hypotheses.”


Contact the author at george@io9.com and follow him on twitter

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