The massive stone heads on Easter Island don’t stare out to sea, but perhaps they should. Residents of what’s also known as Rapa Nui sailed back and forth to the Americas hundreds of years before European explorers first reached the isolated Polynesian island in 1722, a DNA study suggests.

Genetic ties between present-day Easter Islanders and Native Americans indicate that members of these populations mated between roughly 1280 and 1495, says a team led by geneticist Anna-Sapfo Malaspinas of the Natural History of Denmark in Copenhagen. Previous archaeological and genetic evidence suggested that Polynesians first settled Rapa Nui around 1200.

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Rapa Nui navigators probably made the 3,700-kilometer sea trek by canoe to the Americas and then returned home one or more times, the researchers report in the Nov. 3 Current Biology. Previous computer simulations concluded that a vessel sailing east from Rapa Nui would reach the Americas in two weeks to two months.

Even though Easter Islanders found their way home across the waves, westward ocean voyages by Native Americans to Rapa Nui were unlikely, the scientists say. The 163-square-kilometer island is an earthen speck in the vast South Pacific that is easy to miss.

Earlier evidence suggesting that South Pacific islanders voyaged to the Americas — such as DNA signs that chickens reached Chile from Polynesia by 620 years ago (SN: 6/9/07, p. 356) — has proven controversial.

Malaspinas and her colleagues compared more than 650,000 DNA markers at various locations across the genomes of 27 present-day Rapa Nui natives, 17 Native Americans and 172 other people from East Asia and other South Pacific islands. Genetic markers occur in distinctive patterns in various populations and can be used to estimate DNA contributions of one population to another.

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Rapa Nui people display an average of 76 percent Polynesian ancestry, with genetic contributions of 16 percent from Europeans and 8 percent from Native Americans, the researchers say.

The researchers calculated the time when Native Americans mated with Easter Islanders by using clues to the age of DNA segments inherited by one population from another, such as the tendency of these genetic fragments to become smaller in successive generations.

A second study in the same Current Biology, also led by Malaspinas, finds that two 16th to 18th century skulls from a Brazilian group known as Botocudos display entirely Polynesian ancestry. Although the genetic origins of these people can’t be pinpointed to a particular island, it’s likely that Botocudos people reached South America via Polynesian seafaring, Malaspinas says. Radiocarbon dating of the skulls indicates the two individuals died before 1760, when European trading ships began crossing the Pacific.

“These are provocative findings that point to the need for studies of ancient DNA collected from skeletons of Easter Islanders, other Polynesians and Native Americans,” says archaeologist Carl Lipo of California State University, Long Beach.

Sweet potatoes, which originated in South America, turned up in Polynesia as early as 1,000 years ago. Polynesian sea voyages, launched from Rapa Nui and other islands, may have enabled trading for sweet potatoes and intermarriage, Lipo says.

Editor’s Note: This article was corrected October 24, 2014. It originally said the Easter Island statues stare out to sea.

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A version of this article appears in the November 29, 2014 issue of Science News.

J.V. Moreno-Mayer et al. Genome-wide ancestry patterns in Rapanui suggest pre-European admixture with Native Americans. Current Biology. Vol. 24, November 3, 2014, p. 1. doi:10.1016/j.cub.2014.09.057. 

A.-S. Malaspinas et al. Two ancient human genomes reveal Polynesian ancestry among the indigenous Botocudos of Brazil. Current Biology. Published online October 23, 2014. doi: 10.1016/j.cub.2014.09.078.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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