Sweet potato migration to Polynesia

Over 800 presentations will be made at the Botanical Society of America meetings this week, so there is no shortage of things to learn. Today there was a symposium on the botany of economically important plants to honor Charlie Heiser, a tribute to the late botanist organized by his students. He wrote several great little books, so google him to find them. One of the talks presented considered whether or not the sweet potato, native to South America, got to Polynesia in pre-historic times, i.e., evidence of Polynesian contact with South America. One interesting fact is that the name of sweet potato, kumara, or linguistic derivatives was spread across the Pacific. But botanists, while intrigued by such findings, want more definitive data. And the DNA complied. You see, the problem was that sweet potatoes also spread around the world going east and they were taken around Africa and introduced into SE Asia by the Portugese but that would be during the 1500s. The DNA data clearly distinguishes these more recent introductions from those that came probably some 2500 years earlier. Polynesians apparently reached the Cook Islands and Hawaiian Is. no later than 800-1000 years ago, but the Cook Is. are still a long ways from S. America. But look where the Hawaiian Is. are! This is great because the Phactor doesn't need to change that bit of lecture, just add some new confirming data. But the one new thing learned was the sweet potato is still called kumara in New Zealand!

Yams are not sweet potatoes and vice versa!

There in the 1st chapter of this book on plants is the phrase, “consider sweet potatoes in the genus Dioscorea” (Food of the Gods by T. McKenna), but considering the pseudoscientific approach this author takes such errors are not unexpected (must be his non-rational reality – seriously). So the Phytophactor shall endeavor to straighten this out.
Sweet potatoes are not yams; Dioscorea is the genus of yams, one of which is pictured here. Sweet potatoes are Ipomea batatas in the morning glory family (dicots). Yams are monocots. Sweet potatoes are storage roots (although at the root-stem junction) and yams are modified stems (tubers). See the nodes (“eyes”)? What you get in North American markets are sweet potatoes, and yes, the larger, fleshier varieties are called “yams” but they aren’t yams. And those “candied” yams in cans are sweet potatoes too.

The discerning among you will have noticed that the native name for sweet potatoes "batatas" was preserved in the scientific name, and you guessed it, this common name was misapplied by Europeans to another plant native to the same region (Peruvian South America) Solanum tuberosa, the "potato", which is not Irish in the least.