Naturam expellas furca, tamen usque recurret.
–Horace, Epistles, 1:10
The above epigraph, a Latin proverb from the poet Horace, translates, “You can try to drive out nature with a pitchfork, yet nature will always return.” Or as my colleague Bill Hurlbut at Stanford University, a physician and ethicist, likes to say, “Human nature always bats in the bottom of the ninth inning.”
My purpose here is to look at what science, medicine, and psychiatry can tell us about biological differences between men and women and some of the implications for those differences beyond simply our role in reproduction.
Biology and Sex Differences
Sex differences between men and women are not confined to the reproductive organs. They run through all levels of human biology—from subtle features of organs and tissues to differences on the cellular and molecular level. It turns out that aside from our reproductive organs, the most sexually differentiated human organ is the brain. The differences are not just physical but also psychological, influencing our cognitive, behavioral, and emotional functioning.
There are important and measurable sex differences in our experience of emotion, memory, vision, and hearing. Men and women differ in our perceptual processing of faces, in pain perception, navigation, neurotransmitter levels in our brain, and the effects of stress hormones our bodies. We are prone to different diseases, and we respond differently to the same medical treatments.
Many of these differences are innate rather than acquired—they are present from before birth and persist throughout life. Keep in mind also that these differences are subtle, and we should not exaggerate them, as sometimes happens in popular treatments of this issue—“Men are from Mars and women are from Venus,” and so forth.
There is also considerable intrasex variation—sex traits exist on a bell curve, with considerable overlap between the sexes. One mistake that gender ideology makes is the notion that a man with some characteristically feminine traits or interests is “really a woman,” and vice versa. This is not true: he is simply a man at the tail end of this normally distributed bell curve—a boy who likes ballet, or a girl who likes football. That’s all.
Gender ideology fails to acknowledge the full extent of intrasex variation (and overlap between the sexes) in gender-specific traits. In this way, transgenderism ironically “defines” male and female too narrowly.
