Neil Shubin and Sean Carroll discuss homeobox genes, a set of genes that produce basic body parts in all animals, in this video from Evolution: "Great Transformations." In 1994, Walter Gehring discovered the eyeless gene, which guides formation of fruit fly eyes. As an experiment, Gehring put a mouse's eyeless gene into a fruit fly, resulting in normal fruit fly eyes. The same holds true for homeobox genes for wings, legs, even heads. This discovery indicates that animals descended from a single common ancestor that passed along to them a set of homeobox genes, used to build a wide variety of forms from just a few basic body plans.