In the early days of the American Republic, one tiny, red fruit would become a fixture of the fall harvest and a mainstay of holiday meals. The cranberry -- one of only a few commercial fruits native to North America -- might have even sat beside a roast turkey at the first Thanksgiving feast.

But how did the tart cranberry become an industrial crop with 800 million pounds grown annually, when other native fruits are so much sweeter? It wasn't just the health benefits, clever marketing, or grandma's cranberry chutney -- it was a happenstance of evolution. Cranberries float.

"Cranberries are very much associated with water," said geneticist Nick Vorsa, who directs the Philip E. Marucci Center for Blueberry and Cranberry Research in Chatsworth, N.J. "You don't find it very far away."

While other fruits like apples can also float, cranberries float particularly well because of little air pockets at their core.
Like many species of plants native to North America, the cranberry is specially adapted to wetlands -- water-soaked areas that create transition points between dry land and open water. But cranberries do not grow directly in the water.