Did Easter Islanders Mix It Up With South Americans?
The scattered islands of the vast Pacific Ocean were settled by seafarers who set out from the eastern coasts and islands of Asia and traveled thousands of kilometers by boat. Meanwhile pre-Columbian South America was populated by people who crossed a now-vanished land bridge far to the north. Did these two groups ever meet in the New World? There's a good chance of that, according to a new study, which finds evidence that Easter Islanders may have reached South America and mixed with the Native Americans already there.
University of Oslo immunologist Erik Thorsby first began analyzing the people of Easter Island in 1971 to see if he and colleagues could detect traces of an early contribution of Native Americans to Polynesians. He believes that his recent finds may show that Native Americans may have accompanied Polynesians from the coast of South America to Easter Island before the arrival of Europeans.
The island, also called Rapa Nui, is a remote and rocky place 3700 kilometers west of the coast of South America. The people were forcibly deported to Peru in the 1860s and enslaved; therefore, evidence of mixed Polynesian and Native American genes may stem from this time. But Thorsby was able to use blood samples from the islanders, collected since the 1970s, to examine their DNA for particular genetic markers.
As expected, the majority of markers pointed to genes common in other Polynesians. But human leukocyte antigens—a group of genes that encode proteins essential to the human immune system—in the samples showed that a few individuals had a type, or allele, found among only Native Americans. The alleles in question were found on two different haplotypes—a set of alleles inherited by an individual from a single parent—in unrelated individuals. This and other circumstantial genetic evidence suggests that the alleles are older and were introduced centuries before the islanders were sent to Peru by Europeans, Thorsby reports today in thePhilosophical Transactions of the Royal Society B. "The results of our studies suggest that Polynesians visiting South America in the 1400s to 1500s may have taken some American Indians with them upon their return" back to Easter Island, he said in an e-mail from there, where he is conducting further research. That conclusion, he adds, is "speculative."
Scholars have seen some other hints of contact between Polynesians and the people of the New World. Some plants, such as the sweet potato, originated in the Andes Mountains but apparently spread across the Pacific Ocean before the arrival of Columbus. Researchers have noted hints of linguistic and artistic similarities between the western South American and the Polynesian culture. But definitive archaeological evidence is lacking. Finding genetic proof of Native American and Polynesian mixing prior to Columbus's arrival in the New World in 1492 would demonstrate that Polynesians had the capacity to reach South America.
Still, Thorsby's assertion is being greeted with polite skepticism from one scholar familiar with Easter Island's past. "It is good to see this kind of research, but a definitive answer isn't really possible given the lack of chronological control," says archaeologist Terry Hunt of the University of Hawaii, Manoa, who has worked extensively on the island. He says that Thorsby's data don't preclude the possibility that the mixing between these groups occurred later, after Europeans arrived. "Native American genes reaching Rapa Nui with European contact cannot be ruled out." He says what's needed to prove the theory are skeletons that predate the European arrival in 1722. But so far, most of the few remains seem to be later. "The odds are not great" of finding ancient human bones that might yield DNA, he adds. Thorsby acknowledges that more DNA studies of ancient material are needed but remains hopeful that he can clinch the case.
It is now generally accepted that Polynesia was first settled by peoples from southeast Asia. An alternative that eastern parts of Polynesia were first inhabited by Amerindians has found little support. There are, however, many indications of a ‘prehistoric’ (i.e. before Polynesia was discovered by Europeans) contact between Polynesia and the Americas, but genetic evidence of a prehistoric Amerindian contribution to the Polynesian gene pool has been lacking. We recently carried out genomic HLA (human leucocyte antigen) typing as well as typing for mitochondrial DNA (mtDNA) and Y chromosome markers of blood samples collected in 1971 and 2008 from reputedly non-admixed Easter Islanders. All individuals carried HLA alleles and mtDNA types previously found in Polynesia, and most of the males carried Y chromosome markers of Polynesian origin (a few had European Y chromosome markers), further supporting an initial Polynesian population on Easter Island. The HLA investigations revealed, however, that some individuals also carried HLA alleles which have previously almost only been found in Amerindians. We could trace the introduction of these Amerindian alleles to before the Peruvian slave trades, i.e. before the 1860s, and provide suggestive evidence that they were introduced already in prehistoric time. Our results demonstrate an early Amerindian contribution to the Polynesian gene pool on Easter Island, and illustrate the usefulness of typing for immunogenetic markers such as HLA to complement mtDNA and Y chromosome analyses in anthropological investigations.
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