Biological research on homosexuality: Ansell's cow or Occam's razor?

Research based on the assumption that homosexuality can be traced to heredity, prenatal brain differentiation, or effects of gonadotropins in adulthood is reviewed. From a biological standpoint the studies are deficient in several respects: More or less accurate methods of hormone assay, uncertainty over the process of brain sexual differentiation in humans, lack of agreement regarding the role of various gonadotropins in human behavior, small samples, and lack of controls. Moreover, the biological research is based on unwarranted assumptions about human sexuality, sex differences, and sexual orientation that have been imported from the social sciences and popular beliefs. The article questions why a biological basis for sexual orientation is expected, why biologists try to explain homosexuality but not heterosexuality, and what biologists mean by "homosexual." The author concludes that the biological research on homosexuality shows the ineluctable taint on "objective" science of personal beliefs and cultural prejudices.