The Galápagos archipelago is a series of islands off the coast of South America. Finches first came to the Galápagos from a population on the mainland of South America. As they spread from island to island, they encountered different environments, including available food sources, which influenced bill size and shape in each new island population. As separated finch populations evolved in different food environments, they diverged from their ancestral population to have smaller, pointed bills for insects, longer bills for cactus fruit and flowers, or thick, strong bills for hard seeds. In addition, they evolved such that the separated populations could not interbreed. At least 13 finch species have diverged from the original South American species.