Illustration: Cathy Wilcox
We all know why the chicken crossed the road but how the chicken crossed the vast expanse of the Pacific Ocean is a riddle Australian scientists may have finally answered.
University of Adelaide archaeologists have retraced the movement of the domesticated bird based on genetic samples of ancient and modern chickens. The findings allow scientists to reconstruct the migratory patterns of their human carriers throughout Island South-East Asia, Micronesia and Polynesia more than 3000 years ago.
"The colonisation of the remote Pacific was one of the last great human migrations," said the study leader, Alan Cooper, of the Australian Centre for Ancient DNA.
But Professor Cooper said questions remained over the timing and routes used by these people, who travelled using outrigger canoes, relying on currents, wind patterns and the stars to navigate.
Using DNA samples from the bones of ancient and modern chickens, the group identified the genetic signatures of the original Polynesian chickens, which the group used to retrace the early migrations of Polynesians, known as Lapita people.
More than 3200 years ago, the chicken popped up in the Bismarck Archipelago, a group of islands above New Guinea. It then travelled with humans to islands in West Polynesia including New Caledonia, Tonga, Samoa, Fiji and Vanuatu.
Almost 1500 years later, humans, with their chickens in tow, ventured further east to another group of islands now known as French Polynesia. But their exploration did not stop there.
About 50 years later, the Polynesian chicken could be found as far north as Hawaii, as far east as Easter Island and as far south as New Zealand.
"The remarkable thing is that this breed is still alive today. In some of the remote Pacific Islands this thing is quite common," said Professor Cooper, whose results are published in the Proceedings of the National Academy of Sciences journal.
While the researchers are not certain when and by what route the bird arrived in the Bismarck Archipelago, they did trace its origins back further than 3200 years ago to the Philippines.
"We know from archaeology that the Lapita group, the first people moving across this area were really closely associated with carrying pottery, pigs, chickens and rats," he said.
Chicken bones were more common than human remains which made them easier to study.
The birds also had greater genetic diversity than other animals that travelled with humans.
The study analysed the mitochondrial DNA, which is passed down via the mother, from ancient chicken bones uncovered in Hawaii, Niue and Easter Island as well as modern varieties.