An informal, first-person account of the discovery of a genetic link to male homosexuality by a scientist who has given thought to the ramifications of his findings. With the help of Scripps-Howard journalist Copeland, Hamer, a molecular geneticist who heads the National Cancer Institute's section on gene structure and regulation, describes in just the right amount of detail how he put together his research project on homosexuality. He relates how he obtained approval, funding, a research team, and a place to work; how he found the volunteers he needed (gay brothers willing to give blood samples and answer a lot of very personal questions); and what he learned from them and their family trees. Genetics being a statistical science, there's a fair amount of discussion of statistical techniques, but happily this is mostly presented with the general reader in mind. Hamer's account offers a glimpse into both the collegiality and the politics of science, and there's a delightful chapter on a confrontation he had at Harvard with critics of his research. The final portion of his book presents theories about how genes may influence sexual behavior and other human attributes and speculation about the implication of his research. In July 1993, in the midst of intense public debate over gays in the military, the journal Science published Hamer's paper, ""A Linkage Between DNA Markers on the X Chromosome and Male Sexual Orientation."" Tabloids and TV talk shows took it from there. Hamer does not dwell on his time in the spotlight, but the experience evidently sharpened his awareness of public concerns and misconceptions. After noting the possible misuses of genetic research, Hamer concludes that the real danger lies in not studying sex at all. Appendixes include the Science article (not seen) and the interview questionnaire used with research participants. Nothing to titillate, but plenty to think about.