The products of natural, and human, selection are all around us. Humans have transformed wild plants into useful crops by selective breeding and produced domesticated animals with sizes and shapes very different from their wild ancestors. Genetic crosses suggest that relatively few genetic changes are needed to dramatically transform the shape and structure of plants and animals. Natural selection in wild populations can also generate amazing diversity in a surprisingly short amount of time. David M. Kingsley, Ph.D. explains the genetic studies suggest that major evolutionary changes are controlled by a few key genes. From the Series:HHMI’s Understanding Biomedical Research Series