Before most of you were born, I was reading Thor Hyerdahl, particularly his book Kon Tiki. It is very gratifying to read of DNA analysis that at least partially vindicates Hyerdahl's theories regarding contact between South America and Easter Island (also known as Rapa Nui).
DNA analysis of Polynesians and Native South Americans has revealed an ancient genetic signature that resolves a long-running debate
(Nature) For many years, scholars have speculated about how Polynesia was initially populated. Writing in Nature, Ioannidis et al.1 describe a genetic approach that they used to address the issue of Polynesian origins and interactions.
The early peopling of Polynesia attracted worldwide interest in 1947, when the Norwegian explorer Thor Heyerdahl set sail on the Kon-Tiki expedition to test his migration theory2. The crew left Peru on a wooden raft, and after 101 days and a voyage of more than 7,000 kilometres, they reached Polynesian shores, thus demonstrating the possibility of early travel from South America to these Pacific islands. Heyerdahl challenged the scientific community’s view that evidence pointed instead to the peopling of Polynesia by people travelling east from Asia, and his idea that Polynesia was initially populated by South Americans was generally criticized by scholars.
The same scientific community nevertheless discussed cultural contacts between the two regions, because a South American plant, the sweet potato, has a long history of cultivation in eastern Polynesia. The idea that Polynesians voyaged to South America and introduced the plant on their return to Polynesia became the accepted explanation for this3. Rapa Nui (also known as Easter Island) is the best-known example considered concerning such contacts4. It is a part of Polynesia that is located relatively close to South America, and in Rapa Nui there is evidence of large, ancient sweet-potato fields, extraordinary old stonework and a specific birdman cult — all of which are features in common with those of South America.
(A.G.) Ioannidis and colleagues analysed the DNA of people from Rapa Nui, and also studied DNA of individuals from 17 populations of Pacific islands and 15 Native American populations from the Pacific coast of South America. Genome-wide DNA analyses of 807 people (analysing predominantly present-day individuals) enabled the authors to search for evidence of ancestors from different populations who produced offspring together — thereby generating a combined genetic signature of the two populations, described as an admixture. The authors compared the dominant Polynesian DNA markers with those of people from other regions, including Europe, America, Africa and Melanesia. A computational method called an ADMIXTURE analysis allowed Ioannidis and colleagues to work out a person’s probable genetic ancestry and ancestral geographical origins through studies of gene flow. Their main discovery is that several eastern Polynesian populations have signs of a background signature (genetic traces from distant ancestors) that originated from Native South American people.