Ideas that add up #109

Genetic data on 27 Easter Island natives indicated that interbreeding between the Rapa Nui and native people in South America occurred roughly between 1300 and 1500.

“We found evidence of gene flow between this population and Native American populations, suggesting an ancient ocean migration route between Polynesia and the Americas,” said geneticist Anna-Sapfo Malaspinas of the Center for GeoGenetics at the University of Copenhagen, who led the study.

…The researchers concluded that the intermixing occurred 19 to 23 generations ago. They said Rapa Nui people are not believed to have started mixing with Europeans until much later, the 19th century. Malaspinas said the genetic ancestry of today’s Rapa Nui people is roughly 75 percent Polynesian, 15 percent European and 10 percent Native American.

Will Dunham, Reuters, 23rd October 2014

This sent me back to the chapter on Rapa Nui, aka Easter Island, in Jared Diamond’s Collapse — a classic case-study in unintended ecocide.

Analysis of pollen grains in soil and sediments shows that the island’s subtropical forest, including a variety of now-extinct indigenous tree species and other tree species shared with other Polynesian islands, had declined then vanished one or two centuries before the Dutch explorer Jacob Roggeveen rocked up in 1722. Deforestation coincided with a protracted social, political and economic crisis, featuring war and starvation, during which the population fell from up to 30,000 people to several thousand only. Loss of trees is apparently a common factor among collapsing civilizations. 

The island was one enormous final leap eastwards, 1,100 miles, beyond the Pitcairn group at the eastern end of the Polynesian chain, and there seems to have been no commerce or migration between Rapa Nui and other islands during the period of crisis. In fact, the absence of archaeological evidence for trade between Rapa Nui and anywhere in Polynesia has, until now, encouraged an assumption that the island was colonized once only, following a planned migration from Mangareva in the Pitcairn group, and that the population then flourished and collapsed in eerie isolation. 

The survivors encountered by Roggeveen, having long-since lost their source of trunks for ocean-going outriggers, had only short, leaky canoes made of uncaulked planks bound with plant stems, just about sufficient for paddling inshore but no use for catching tuna and porpoises — the main source of protein for earlier generations — let alone undertake ocean voyages. 

Which makes this University of Copenhagen study astonishing. A further 2,300 miles of Pacific Ocean separate Rapa Nui from what is now Chile. If the genes don’t lie then Rapa Nui trade canoes must have brought South American women back to the island, probably more than once — a formidable but not inconceivable feat of navigation for Polynesian seafarers — early on in the colony’s history, while the population was small enough to be significantly influenced by the new blood. 

Tantalizing circumstantial evidence supports the story:

  • the beautifully fitted stone facing of some ahu platforms (on which the moai stood, facing inland) resembles Inca architecture, according to Diamond — though he scoffs at Thor Heyerdahl’s attempt to attribute the islanders’ monolith-carving skills to South American antecedents
  • the (South American) sweet potato seems to have spread across Polynesia before European sailing ships first plied the Pacific.
  • “The islanders’ nonchalant, unafraid, curious reaction to Roggeveen does suggest prior experience of Europeans”, writes Diamond, “rather than the shocked reaction expected for people who had been living in total isolation and had assumed themselves to be the only humans in the world” — though in the light of this new study it could be that their reaction spoke of prior experience of sea-borne arrivals, not limited to Europeans. 

The “mystery” element of Rapa Nui just got less mysterious, and more interesting.

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