This sounds like a credible alternative to me:<p>> <i>Dr. Kistler argued that it was still possible that Pacific Islanders voyaged to South America and returned with the sweet potato.</i><p>> <i>A thousand years ago, they might have encountered many sweet potato varieties on the continent. When Europeans arrived in the 1500s, they likely wiped out much of the crop’s genetic diversity.</i><p>> <i>As a result, Dr. Kistler said, the surviving sweet potatoes of the Pacific only seem distantly related to the ones in the Americas. If the scientists had done the same study in 1500, Pacific sweet potatoes would have fit right in with other South American varieties.</i><p>I remember an issue of National Geographic that had a photo montage of about 40 different kinds of potatoes that are still being cultivated in the Andes today. They didn't have any sweet potatoes(1) but I can imagine that in 1500 there were as many different sweet potato variants being cultivated in various places in the new world.<p>(1) Sweet potatoes are not a variety of potato, so this isn't surprising.