The Surprising Ingredient That Helped Polynesians Conquer the Pacific

Sweet potatoes are a very versatile tuber. You can roast them. You can bake them into a pie. You can turn them into the third best type of french fry. And apparently, you can make them an integral part of colonizing Polynesian islands.

Sweet potatoes are not indigenous to Polynesia, having arisen thousands of miles away in Central and South America. Even so, the tasty root vegetable has become a staple of the islands’ cuisine. While it was known that the crop had arrived in eastern Polynesia some time after human settlement in 900 CE, and then spread westward towards New Zealand, scientists have debated exactly how and when it got there. Some evidence suggests sweet potato seeds reached the region through natural means, such as birds, wind, and sea currents. Now, new research hints that the crop’s presence was a major factor in enabling human expansion across the Polynesian islands.

A team of archaeologists, led by University of Otago professor Ian Barber, scoured the New Zealand island Te Wāhipounamu for remains of ancient kūmara, as the Maori call sweet potatoes. They found what they were looking for at Triangle Flat, an area that was once home to a Maori farming complex. In the sand, they located sweet potato granules, which they then carbon dated.

Results showed that the crop could have been planted as early as 1290 CE, over 100 years earlier than previously believed on the island, and around the same time that settlers first began colonizing the southernmost Polynesian islands. As Barber wrote in his ensuing study, published Wednesday in the journal Antiquity, the findings suggest sweet potatoes were among the first crops planted by colonizers. In fact, the availability of sweet potatoes as a crop may have been among the factors that made settling the islands possible in the first place.

The vegetable is known for its hardiness, as well as for the speed at which it grows. Polynesia is a vast network of over 1,000 islands, and settlers needed hardy crops to sustain themselves as they spread to new territories with cooler climates than those of islands nearer the equator. In a press release, Barber suggested that Polynesians may have been galvanized by the knowledge they had such a robust food source at their disposal.

“American sweet potato resilience, as bequeathed by continental evolution, may have helped motivate early migrants to cross cooler waters for southern Polynesian islands where kūmara would outperform,” he said.

There could be some greater impacts of Barber’s research. According to the International Potato Center, more than 105 million metric tons of the crop are produced globally each year, making it the world’s fifth largest crop. Climate change, however, threatens to affect production, as regions that produce a large amount of the supply could warm dramatically by 2070. Barber expressed hope that studying the spread of sweet potatoes could uncover new ways to improve the crop’s resilience. If that happens, you’ll know who to thank for saving your favorite Thanksgiving side dish.