People in the United States celebrate Thanksgiving each year with a feast that includes pumpkins. But it turns out that pumpkins—along with the rest of Cucurbita, the plant genus that includes gourds and squash, have us to thank, too. More than 10,000 years ago, the extremely bitter-tasting wild ancestors of Cucurbita plants were thriving across the New World, along with the large mammals such as giant sloths and mammoths that grazed on them. Today those wild plants are rare, whereas the sweet-tasting domesticated species are extremely common—in our gardens, that is. What would have happened to pumpkins, gourds, and squash without human intervention? A genetic analysis of 91 Cucurbita species paints a dark picture. One finding is that the plants weren't domesticated once but several times by the native people of the New World. Seeds uncovered with ancient archaeological remains even point to a previously unknown domestication event in Mexico. And there were many more ancient varieties around until about 10,000 years ago. So what changed? Those giant mammals that ate the bitter Cucurbita fruit and dispersed their seeds all went extinct. The smaller mammals that took over in the Americas are thought to be far more sensitive to bitter-tasting plants, since they carry more genes for bitter taste receptor proteins compared to the extinct giants. Without the seed dispersal service of giant mammal poop, those plants got crowded out of the landscape. Many went extinct and the rest are almost gone. As reported online today in the Proceedings of the National Academy of Sciences, pumpkin, squash, and gourds would likely have gone the way of the dodo were it not for humans domesticating them. There is much to be thankful for, even if you're on the menu this Thanksgiving.
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