While socially we divide people by gender, the balance of nature vs. nurture definitely leans toward nature—the imbalance between male hormones—testosterone, etc.—and female, an imbalance beginning in the womb, will determine one’s predilections, in fact will determine which set of organs will develop. By the simplest Darwinian reasoning, it is obvious why the “norm” is heterosexuality, but several factors complicate this Manichean thinking: First, our tendency to divide everything into two mutually exclusive kinds obfuscates the fact that each of us has both male and female chemistries in us, and often even organs. Secondly, gender is confused with social roles—“Men are strong and therefore do heavy work; Women are weak and therefore do secretarial work, etc.”—and all the other oversimplifications that make a society a slow, plodding organism. Sexual preference is strictly biological; how one acts out one’s sexuality in society is mostly nurtured and learned by the reward-and-punishment system built into human behavior. The factors that account for acting on one’s sexual orientation, then, are both biological and social, but the orientation itself can be anywhere on the range between two extremes. What is scientifically clear is that one’s psychological orientation cannot be changed by will power.