Presidential fantasies regarding gender and sex

President Donald Trump has declared that what science knows about sex is wrong. Following his executive orders limiting transgender rights, the Department of Health and Human Services updated its official definitions of sex: female and male, reiterating the administration's stance that male and female are the only two sexes and that they cannot be changed. The unqualified ‘scientist,' Robert F. Kennedy Jr., declared: "This administration is bringing back common sense."

First, common sense is not the place to look to understand either sex or gender; one society’s understanding of both is often different from another’s. Second, science knows quite well what sex is and why it sometimes doesn’t fit into two clean categories of male and female. Third, gender is a cultural and social concept which most assuredly is not simple, binary or even stable depending on history, geography and even fashion trends.

Let's get clear the difference between sex and gender. Sex is a biological concept — in recent decades determined by identifying and counting chromosomes, the blobs in our cells made up of the genes that partially make us who we are. In humans, there are typically, but not always, 23 pairs for a total of 46. One pair are named by convention as the sex chromosomes because they greatly influence whether someone is born male or female. Females generally have two X chromosomes, while males usually have one X and one Y.

Gender, on the other hand, has little to do with genes, chromosomes and biology. It is all about culture and how we choose to identify and classify one another.

In the U.S., one sign of gender used to be hair length — men short, women long. But it wasn’t always so. Our founders wore their hair long, as did men in many cultures throughout history. What you wear, what sports you pursue, what hobbies you enjoy, what occupations are available for you, whether you act aggressively or not, help raise children or not, and even what you prefer to eat all contribute to your gender identification. You may want to be more feminine or you may seek to appear as ultramasculine. These categories are completely fluid, established by customs and traditions, and can and do flip from year to year.

As for sex, surely biology teaches that male and female are determined from birth, clearly distinct and don’t overlap? Nope, biology teaches no such thing.

In species that produce litters of many young from each pregnancy, including rats, gerbils, and mice, the fetuses are arranged like peas in a pod inside the mom’s uterus. This grouping results in female and male fetuses residing next to one another. Steroid hormones produced by one fetus' developing sexual organs influence and change the developing neural and sex structures in the adjacent fetuses. Genes aren’t the whole story. That is why plenty of animals in nature exhibit different structures and behavior regardless of their biology.

There is plenty to argue about regarding how to treat sex and gender in our lives, from whether someone should change their gender or which bathrooms or pronouns are available to whom. I favor tolerance since some of sex and all of gender are so fluid. Others may want to fight cruel culture wars that make pariahs out of kids and neighbors who aren’t clearly in either basket. No one in these debates should be allowed to draw bogus lines in the sand to try to win points.

This guest essay reflects the views of Arthur L. Caplan, head of the Division of Medical Ethics at NYU Grossman School of Medicine.