Evolutionary biologists increasingly accept that genes are selfish. But what does this mean? Clearly genes do not have personal motivations, and even if they did, they could not achieve their designs without cooperation of the bodies in which they reside. In the most general sense, genes are merely blueprints, or, better, recipes, for the production of proteins. As such they influence the anatomy and physiology of living things including not only structural proteins but also enzymes and other factors that underlie the functioning of organisms. Genes ultimately affect the structure of kidneys, as well as the structure of nervous systems. Genes thus influence kidney function, just as they influence central nervous system function. When the central nervous system functions, behavior results. In this sense, genes are intimately connected to behavior, no less than they are to the physiology and structure of our internal organs.

Organisms are...