In Dangerous Liaisons? Norman C. Ellstrand examines this and other questions, beginning with basic information about the natural hybridization process. He describes what is known about hybridization between the world's most important crops - such as wheat, rice, maize, and soybeans - and their wild relatives. Such hybridization, Ellstrand explains, is not rare, and has occasionally had a substantial impact. In some cases, crop genes have diluted natural diversity to the point that wild populations of certain rare species were absorbed into the gene pool of the more common crop, essentially bringing the wild species to the brink of extinction.