Chicken Bone DNA Shows Columbus Reached South America before Polynesians

A new research that analyzed DNA from ancient chicken bones suggests that Europeans, not Polynesians, were the first to reach South America.

The study, conducted by researchers at University of Adelaide's Australian Centre for Ancient DNA (ACAD), found a unique genetic marker in early Polynesians chickens and used it to trace the movement of chickens across Pacific.

Scientists rely on ancient animal DNA to study the origin and migration of Polynesians. The debate over when chicken arrived in South America has been going on for several years.

Previous research by Alice Storey at the University of Auckland and colleagues had found that ancient Polynesian voyagers had reached the west coast of South America at least a century before Columbus. Storey's study was based on chicken bones found in Chile and was published in the journal PNAS in 2007.

Then in 2008, Alan Cooper of the Australian Center for Ancient DNA in Adelaide, had said that the "unique" mutation found in Chilean chicken was actually an ordinary mutation seen in several chickens around the world.

Now, Dr Vicki Thomson of ACAD and team have challenged Storey's results by suggesting that the chicken bone DNA that they used for their research was contaminated.

For the study, researchers analyzed mitochondrial DNA of 37 chicken bones from the Pacific. The research also included six samples from Rapa Nui used by Storey and colleagues, abc news reported.

"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," said Professor Alan Cooper, Director of ACAD, according to a news release. "We were able to show that the ancient chicken DNA provided no evidence of any pre-Columbian contact between these areas."

Storey, who is now consulting archaeologist in British Colombia, Canada, defended her team's findings. She said that mitochondrial DNA doesn't really provide much information about chicken ancestry and that researchers need to use nuclear DNA from chickens who lived before 1600 to understand chicken migration in the South America, according to abc news. During the 1600s, Europeans started moving around the region.

She added that Cooper and team chose to remove one contamination, but not the other. "You can't pick and choose which contamination you like and which one you don't," she told abc news. "If you are going to exclude one you have to exclude them both."

The study was published in the journal Proceedings of the National Academy of Sciences.