Suggestions that ancient Polynesians had contact with South America could have been biased by contaminated samples of ancient-chicken DNA, say Alan Cooper and Jeremy Austin at the University of Adelaide, Australia, and their colleagues.

The authors sequenced genetic information from 37 ancient chicken bones and 124 modern samples, all from Polynesia and the islands of southeast Asia. They found a unique and distinctive set of DNA variations in all of the ancient and many of the modern specimens. This 'Polynesian motif' is not found in early South American chickens, suggesting that humans transported chickens from Micronesia across the Pacific Ocean, but only as far as Easter Island (Rapa Nui). Contamination of some ancient samples with modern-chicken DNA probably explains previous suggestions that the migration continued all the way to South America, the authors say.

Proc. Natl Acad. Sci. USA http://doi.org/rx6 (2014)