One of the biggest challenges facing anthropologists has been explaining how the Polynesians managed to navigate across thousand of miles of open ocean in small canoes.
Scientists have two rival theories. One suggested that it was gradual, over many thousands of years, and involved several groups of colonisers. The other theory, called the "express train to Polynesia", postulated that it was a rapid affair, taking no more than a few centuries, and involved a single stock of people from South-east Asia.
Archaeological, linguistic and genetic research of present-day Polynesians has given a range of dates for when each island was first colonised.
However, Christopher Austin, an evolutionary biologist from the South Australian Museum in Adelaide, said a genetic analysis of Lipinia noctua, a "vagabond" lizard on Pacific islands that can stow away on boats, suggests the express train theory is correct.
He studied 29 lizards collected from 15 different Pacific islands, spanning Palau in the west to Tuamotu in the east. The results, published in the journal Nature, show that the lizards are so similar to each other that they must have developed very recently from a common population.
The lizard, sometimes called the moth skink, spends much of its time hiding under the bark of trees, and could have stowed away on the canoes of early seafarers.
"All the lizards from the central and eastern Pacific - all the islands east of the Solomon Islands - were nearly genetically identical, demonstrating a close relationship as a result of a very rapid colonisation of the Pacific," Dr Austin said.
"One of the most adventurous and bold episodes in human history was the colonisation of the Pacific islands, and these lizards have provided us with valuable information as to how humans got to these islands."