By Bower, B.
Science News , Vol. 171, No. 23
Thor Heyerdahl got it backwards. More than 40 years ago, the late explorer proposed that the Inca or their predecessors voyaged from South America to Polynesia by raft. On the contrary, a new study indicates that Polynesian seafarers reached what's now Chile by about 620 years ago. That conclusion hinges on the first evidence of when chickens arrived in the Americas.
A team led by anthropologist Alice A. Storey of the University of Auckland in New Zealand used radiocarbon dating and a comparison of ancient DNA to determine a Polynesian origin for a chicken bone previously unearthed at Chile's E1 Arenal site. Mitochondrial DNA extracted from the El Arenal bone contains an exact copy of a genetic sequence that appears in comparable DNA from 600-to-2,000year-old chicken bones found in Tonga and American Samoa. Those islands lie 6,000 miles west of Chile.
Europeans arrived in South America around 500 years ago, after the Inca had incorporated chickens into religious ceremonies, according to Storeys group.
Storey and her coworkers performed radiocarbon dating on one El Arenal chicken bone selected from 50 bones recovered in 2002. The researchers then isolated a particular segment of mitochondrial DNA from the same bone and from 11 chicken bones found at pre-European archaeological sites in Polynesia. They found the same sequence in all the bones.
This stretch of DNA undergoes frequent alterations over generations. Yet the researchers found the same DNA segment in feathers of two living chickens belonging to a blue-egg-laying breed in Chile. Selective breeding may by chance have preserved the Polynesian sequence, the researchers suggest. …