Evidence reported in the journal Current Biology on April 12th shows that sweet potatoes arose before there were even humans around to eat them. It was identified that the sweet potato originated at least 800,000 years ago and is therefore likely that the the edible root had already existed when humans first found the plant.
Robert Scotland from the University of Oxford, and his colleagues, set out to clarify the origin and evolution of the sweet potato. The researchers aimed to explore how sweet potatoes, with an American origin, had come to be widespread in Polynesia by the time Europeans had arrived.
Researchers combined genome skimming and target DNA capture to sequence the whole chloroplasts and 605 single copy nuclear regions from 199 specimens representing the sweet potato and all of its crop wild relatives. The data strongly suggests that sweet potatoes arose after a gene duplication event. It was shown that sweet potatoes arose from its relatives, I. trifida, and later hybridized with it to produce the independent sweet potato lineage. Researchers were able to demonstrate that the existence of the two lineages was the results of an ancient hybridization between sweet potatoes and its progeitor. Therefore, after the two species became distinct, they hybridized explaining how sweet potatoes has arrived in both America and Polynesia.
While the lineage of sweet potatoes might not sound like a significant breakthrough, this challenges the prior long held belief that the sweet potato was taken to Polynesia by humans, implicating there was no contact between Ancient Americans and Polynesians. The evidence that the two groups had contact were considered true based upon the evidence surrounding sweet potatoes, chickens, and humans. Now, evidence from chickens and humans are now questionable. Therefore, the evidence regarding sweet potatoes calls into question the existence of pre-European contacts across the Pacific.
Link to Article https://www.sciencedaily.com/releases/2018/04/180412140845.htm
Original Study: https://www.sciencedirect.com/science/article/pii/S096098221830321X?via%3Dihub