Because genes encode instructions for building animal bodies, biologists once expected to find significant genetic differences among animals, reflecting their great diversity of forms. Instead very dissimilar animals have turned out to have very similar genes. Mutations in DNA "switches" that control body-shaping genes, rather than in the genes themselves, have been a significant source of evolving differences among animals. If humans want to understand what distinguishes animals, including ourselves, from one another, we have to look beyond genes.