Ancient chicken DNA may shed light on the migratory patterns of early Polynesian people.
According to a new study published in the Proceedings of the National Academy of Sciences, ancient Polynesian chickens might not have migrated to South America as some scientists believe. Researchers came to their conclusion after comparing mitochondrial DNA taken from chicken bones from archeological sites in several Pacific islands with DNA taken from 122 feathers from modern chickens in the South Pacific.
"We were able to re-examine bones used in previous studies that had linked ancient Pacific and South American chickens, suggesting early human contact, and found that some of the results were contaminated with modern chicken DNA, which occurs at trace levels in many laboratory components," Professor Alan Cooper of the University of Adelaide's Australian Centre for Ancient DNA said in a statement. "We were able to show that the ancient chicken DNA provided no evidence of any pre-Columbian contact between these areas."
The results showed that the chicken DNA had a distinct genetic marker that is not found in modern South American chickens, which suggests that the Polynesian and South American people did not have much contact.
"Indeed, the lack of the Polynesian sequences [of DNA] in modern South American chickens ... would argue against any trading contact as far as chickens go," Cooper told National Geographic.
By sequencing the ancient DNA, researchers were able to track the early movements and trading patterns in the Pacific.
"We can show [from chicken DNA] that the trail heads back into the Philippines," Cooper said. "We're currently working on tracing it farther northward from there. However, we're following a proxy, rather than the actual humans themselves."
The history behind the settlement of the Pacific Islands remains largely a mystery. Historians have determined the colonizing of the region took place in two phases: The first was more than 3,000 years ago, when seafarers from Papua New Guinea sailed to islands like Vanuatu, Fiji, Tonga, Samoa, New Caledonia and populated them. The second took place around 800 A.D., when settlers came to the islands such as Tahiti, Bora Bora, the Marquesas, Easter Island, and Hawaii. To this day, exactly why and how these voyages were accomplished has left more questions than answers. Very few artifacts or writings remain.
"There are still many theories about where the early human colonists of the remote Pacific came from, which routes they followed and whether they made contact with the South American mainland,” Jeremy Austin, ACAD Deputy Director, said in a statement. “Domestic animals, such as chickens, carried on these early voyages have left behind a genetic record that can solve some of these long standing mysteries."
One lingering question is whether the Polynesian people made it all the way to South America, and if they beat Christopher Columbus to it. The latest study suggests this did not happen, but many scientists disagree.
"The evidence for Polynesian contact with the New World prior to Columbus is substantial," David Burley, an archaeologist at Simon Fraser University in Canada, said. "We have the sweet potato, the bottle gourd, all this New World stuff that has been firmly documented as being out here pre-Columbian. If the Polynesians could find Easter Island, which is just this tiny speck, don't you think they could have found an entire continent?"
Dr. Alice Storey agrees. In 2007, the then-Ph.D. student at the University of Auckland, published a study linking a 600-year-old Chilean chicken bone as having a genetic mutation found in ancient chicken bones found in the Pacific. Cooper has argued her findings did not describe a genetic mutation in the Pacific but one that came from European chickens.
Storey challenges the latest findings, saying that mitochondrial DNA is inadequate at drawing a hard-lined conclusion.
"In chickens in particular we know that mitochondrial DNA doesn't tell us anything about the past," Storey told the Australian Broadcast Corporation.
"People move around chickens all the time," she says. "Modern chicken DNA is this huge hodge podge mix of stuff."