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Sweet Potato Puzzle

The spread of the sweet potato, Ipomoea batatas, has long puzzled scientists, the New York Times writes, and a new genetic analysis of the crop has not solved the mystery.

Indigenous peoples of Central and Southern America grew sweet potatoes for generations when Europeans came upon the crop as they arrived in the Americas, the Times says. But, it notes that Captain Cook also found the sweet potato in Polynesia, where it too had been grown for generations, and others later found them at other sites in the Pacific. As Gizmodo notes, this has led some to posit that Polynesian explorers reached the Americas before Christopher Columbus did.

A genetic analysis of the sweet potato, appearing this week in Current Biology, finds that the plant may have spread of its own accord. Researchers from the University of Oxford analyzed the genomes of nearly 200 sweet potatoes from the Americas and elsewhere collected between 1769 and 2014. A phylogenetic analysis then found that Polynesian sweet potatoes diverged from American ones more than 100,000 years ago — prior to human arrival in either the Americas or Polynesia.

"Our results challenge not only the hypothesis that the sweet potato was taken to Polynesia by humans, but also the long-time argued existence of ancient contacts between Americans and Polynesians," first author Pablo Muñoz-Rodríguez from Oxford says in a statement.

However, the Times notes that not everyone is convinced. Tim Denham, an archaeologist at the Australian National University, calls the scenario in which the wild ancestors of sweet potatoes spread across the Pacific to be domesticated multiple times in similar forms "unlikely."