Plant remains reveal early contact with South America

Archaeologists have discovered that the first inhabitants of Easter Island apparently had contact with South America. Evidence for this comes from small starch grains about 1,000 years old preserved in the sherds of obsidian tools from northern Rapa Nui. Starch granules come from crops typical of the Pacific region, but also from sweet potatoes, cassava and edible canna – plants from South and Central America.

Huge stone heads with big noses and long ears stare down new arrivals: Easter Island's massive stone moose are as mysterious as they are world-famous. But where their makers came from has long been a topic of debate. Norwegian adventurer Thor Heyerdahl believes he saw similarities to South American cultures in the Easter Island statues as well as some linguistic terms. So he assumed that the indigenous people originally came from South America. However, the majority of archaeologists assumed that the settlement of Polynesia and Easter Island came from Asia.

What plants did the first settlers grow?

However, recent genome comparisons show that there must have been actual contact between the Rapa Nui and the indigenous people of South America. However, it remains unclear how and when these contacts took place. Cultivated plants on Easter Island can provide one way to understand this: if you discover which crops the island's first settlers brought with them and cultivated, this also reveals their origin. “Polynesians were great navigators and crossed the ocean in all directions for centuries. They also brought plants and other goods with them,” explain Paloma Berenger of the University of the Christian Humanist Academy in Santiago, Chile, and her colleagues.

To conduct their study, the team analyzed tiny starch grains preserved in 20 obsidian tools from the Anakena site on northern Rapa Nui. These tools – scrapers, knives and drills – come from the oldest layer found at the Aha-Nau-Nau settlement and date back about 1,000 years. They come from the first phase of settlement on Easter Island. “The presence of unmodified starch indicates that these tools were used to process roots, tubers and fruits before cooking,” the scientists explain. Using morphological and chemical comparisons, they were able to determine which plants the starch grains attached to these tools came from.

Sweet potatoes, cassava and canna are from South America

Analysis has shown that early settlers on Rapa Nui cultivated some crops common to the Polynesian Pacific, including yams (Dioscorea alata) and taro (Colocasia esculenta). This is the first evidence from this early period on Easter Island of three plants from Southeast Asia. These include breadfruit (Artocarpus altilis), golden plum (Spondias dulcis) and ginger. But Beringer and her team also identified starch granules from three crops that were native to South America: sweet potato, cassava, and canna, also called achira, or Indian flower ear.

“The introduction of this South American species onto Rapa Nui suggests contact between Polynesian mariners and South American populations,” Beringer and her colleagues wrote. “Our results provide the first evidence that these plant species arrived on Easter Island much earlier than previously thought.” The islanders may have brought these plants with them as travel provisions on their return voyage from a visit to the west coast of South America. It is also conceivable for South American citizens to visit Easter Island. In any case, this study supports the assumption that direct or indirect contacts existed between Polynesian and South American populations from the beginning of Rapa Nui settlement.

Source: PLOS ONE, doi: 10.1371/journal.pone.0298896

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