As a professor of biology and neuroscience at Stanford and a recipient of a MacArthur Foundation "genius grant," Robert Sapolsky carries impressive credentials. Best of all, he's a gifted writer who possesses a delightfully devilish sense of humor. In these essays, which range widely but mostly focus on the relationships between biology and human behavior, hard and intricate science is handled with a deft touch that makes it accessible to the general reader. In one memorable piece, Sapolsky compares the fascination with tabloid TV to behavior he's observed among wild African baboons. "Rubber necks," notes the professor, "seem to be a common feature of the primate order." In the title essay of The Trouble with Testosterone, Sapolsky ruminates on the links, real or perceived, between that hormone and aggression.