The biology of sexual orientation

Simon LeVay, the best-known scientific researcher into the origin and nature of homosexuality, has an Internet home page. It includes a piece on "The Biology of Sexual Orientation" which examines a variety of non-biological theories of homosexuality including psychoanalytic theories, behaviorism/socialization, the effect of sexual experiences, and social Social constructionism. LeVay's look at biological theories includes genes, hormones, anatomy, brain studies, cognitive research, and birth order studies.

Here's a classic but timeless resource on the biological angle. In June 1997's "Homosexuality and Biology," Chandler Burr provides "an introduction to a muddled and sometimes contentious world of scientific research—one whose findings, now as tentative as they are suggestive, may someday shed light on the sexual orientation of everyone..." for The Atlantic.