By Ste­phen T. Asma

"How many genders or sexes are there?" Jaak Panksepp asks his students.

Panksepp, who is the father of affective neuroscience and currently Baily Endowed Chair of Animal Well-Being Science at Washington State University, waits patiently for them to overcome their confusion and venture the obvious answer: "Two."

"No, there are at least four, and probably many more," he informs them. The standard setup is, of course, a male brain in a male body or a female brain in a female body, but we regularly find a brain-body mismatch; feminized brains in masculinized bodies and vice versa.

When I was an undergraduate, studying the humanities, we were taught that being gay was not a biological phenomenon, nor was gender, for that matter. Professors of the humanities and social sciences saw all biological explanations of human behavior as reductionistic and deterministic. If anyone tried to suggest brain-based or neurochemical avenues of explanation, a detour would be erected to take the students into the terrain of psychoanalysis, or social constructionism, or if the professor became too frustrated he would just remind students of social Darwinism, eugenics, and finally stop all such explorations by mentioning Hitler.

Now that I'm a professor, I'm saddened to find that not much has changed in the attitudes of my humanities colleagues—many of whom still vilify biological explanations of human behavior and culture. The Harvard professor of English Louis Menand, for example, a Pulitzer Prize winner, warned humanities departments, in his 2004 MLA talk "Dangers Within and Without," to stay away from biology. But while not much has changed in the humanities and social sciences, a lot has changed in biology. While humanists weren't looking, biology (genetics, embryology, evolution, neuroscience, etc.) left behind many of its deterministic pretensions and embraced the indeterministic developmental logic of epigenetics—the complex interface of nurture and nature. Biology now recognizes the immense domain of external triggers and influences (from intrauterine environment to social structures) that shape phenotypic expression of genetic possibilities. Biology has become dialectical.

How did the humanities and social sciences miss this exciting transformation? In the 1970s and 80s, feminists drew an important distinction and created a new language for fruitful discussion. The distinction drew a line between sex and gender. Sex referred to the reproductive categories of male and female, and it was a useful biological concept, applicable to humans, nonhuman animals, and plants. Gender, on the other hand, indicates the socially constructed roles, behaviors, and traits of male and female. Gender categories may correspond to sex categories, but they need not. This useful distinction, and subsequent academic conversation, were fuller realizations of Simone de Beauvoir's famous 1949 statement, in The Second Sex, that "one is not born a woman, one becomes one." This existential rejection of essentialism sought to break the oppressive tendencies of anybody who used the "nature of woman" as an excuse for mistreatment.

An academic division of labor resulted from this distinction. Sex remained a productive topic (excuse the pun) for biologists, who are interested in the genetic, developmental, and chemical pathways of male/female dimorphism. People in the social sciences and humanities, by contrast, made gender, not sex, the subject of their work. In gender studies, we learn about the ways that men and women "perform" their respective roles—people of male sex can perform as female gender, and vice versa, by adopting modes of speech, dress, behavior, and even values. There is no talk of innate instincts or brain differences in gender studies.

In the 1980s and 90s, psychoanalysis was used to connect gender to early developmental dynamics in the family. Evelyn Fox Keller, for example, argued that men are more detached, objective, and stereotypically scientific, because their identity formation has to detach twice from the mother, while women have to detach only once. We all separate ourselves from mother and thereby attain an ego—a self. But as a boy, I must also detach again, in an unconscious realization that I am not even the same kind of thing as my mother (i.e., I've got this thing between my legs, etc.). Male identity, in this view, is alienated twice from the mother, producing human beings who are more remote, more distant. That is just an example of the sort of dominant, nonbiological explanation of difference that flourished in gender studies.

In addition to these theoretical approaches to gender, much of gender studies focused on the many ways that prejudice informs gender positions and relations. Gender is a politically and socially coerced category, and patriarchy is considered to be an ever-looming threat. Subsequently, issues of power are at the forefront of gender studies, and many theorists have applied the Marxist class-struggle lens to gender issues, substituting men for the bourgeoisie. Contemporary cultural studies, for example, has given itself over almost completely to that approach.