Homosexuality is a problem for evolutionary theory. How does a non-reproductive sexual preference survive? There is increasing evidence for a biological basis to homosexuality, not least the discovery of markers for a gay gene. Yet Darwinism, the most widely accepted evolutionary theory, emphasizes successful reproduction. "Straight Science?" considers the latest research and examines this apparent paradox from an evolutionary perspective.
While social constructionism offers explanations in terms of social learning and cultural preferences, the body of evidence for a genetic predisposition to homosexuality grows. Jim McKnight considers both biological and social evolutionary theories of the causation of homosexuality, and puts forward a model of the most likely causes. He concludes with an overview of the adequacy of a social constructivist view versus a sociobiological one.