The Personality Genes

Molecular biologist Dean Hamer has blue eyes, light brown hair and the goofy sense of humor of a stand-up comic. He smokes cigarettes, spends long hours in a cluttered laboratory at the National Institutes of Health, and in his free time clambers up cliffs and points his skis down steep, avalanche-prone slopes. He also happens to be openly, matter-of-factly gay.

What is it that makes Hamer who he is? What, for that matter, accounts for the quirks and foibles, talents and traits that make up anyone's personality? Hamer is not content merely to ask such questions; he is trying to answer...