From a Few Genes, Life's Myriad Shapes.

This article describes a science field called evo-devo which is the combined study of evolution and development. Evo-devo is the exploration of the process by which a fertilized egg transforms into an adult. Researchers are finding that the evolution of complex forms can be accomplished by a process requiring no more than tweaks to already existing genes. Further, it appears the number of genes that can be tweaked are relatively few.