As they started to populate areas of human habitation, perhaps people started to eat the more palatable, and less bitter ones, starting the long process of domestication. But, Kistler points out that because of their incredible bitterness, it's more likely that "initial use of Cucurbita by humans might not have been for food, but for tools and containers." Eating came later. Either way, once humans stepped in as seed dispersers for the fruits, their survival was ensured (albeit not before most of the species went extinct). Including the ancestors of our beloved pumpkins and squash.