There is no gene for such unambiguous bits of morphology as your left kneecap or your fingernail. […] Hundreds of genes contribute to the building of most body parts and their action is channeled through a kaleidoscopic series of environmental influences: embryonic and postnatal, internal and external. Parts are not translated genes, and selection doesn't even work directly on parts.

"Caring Groups and Selfish Genes", p. 91 - The Panda's Thumb (1980)