Early Americans helped colonise Easter Island

South Americans helped colonise Easter Island centuries before Europeans reached it. Clear genetic evidence has, for the first time, given support to elements of this controversial theory showing that while the remote island was mostly colonised from the west, there was also some influx of people from the Americas.

Easter Island is the easternmost island of Polynesia, the scattering of islands that stretches across the Pacific. It is also one of the most remote inhabited islands in the world.

So how did it come to be inhabited in the first place? Genetics, archaeology and linguistics all show that as a whole, Polynesia was colonised from Asia, probably from around Taiwan. The various lines of evidence suggest people began migrating east around 5500 years ago, reached Polynesia 2500 years later, before finally gaining Easter Island after another 1500 years.

But the Norwegian adventurer Thor Heyerdahl thought otherwise. In the mid-20th century, he claimed that the famous Easter Island statues were similar to those at Tiahuanaco at Lake Titicaca in Bolivia, so people from South America must have travelled west across the Pacific to Polynesia. His famous Kon-Tiki expedition, in which he sailed a balsa wood raft from Peru to the Tuamotu islands of French Polynesia, showed that the trip could have been made. But if it was made, no trace remained.

Now Erik Thorsby of the University of Oslo in Norway has found clear evidence to support elements of Heyerdahl's hypothesis. In 1971 and 2008 he collected blood samples from Easter Islanders whose ancestors had not interbred with Europeans and other visitors to the island....