What our culture believes about biology’s influence on our behavior is critical to how we see the world, particularly in the area of sex, sexuality, and gender. When I first began teaching in the sixties, theories were still limited by a language steeped in heteronormativity. Chromosomes, hormones, and genitalia defined only two sexes: male and female. Biology was given primacy in explaining and justifying the ways in which gender (masculinity and femininity) was expressed and organized, especially, but not only, in sexual and familial arrangements. The demands of a patriarchal and heteronormative culture in shaping gender behavior were rarely a match for the belief that our hormones made us do it.
By the end of the sixties a women’s studies critique gave ample evidence that biology alone could not explain gender differences. In fact, evidence indicated that on almost any characteristic or attribute—physical or psychological—the differences among women and among men were greater than between them. On every dimension, a continuum (rather than a dichotomy) best described gender differences. Sex-designation at birth was not necessarily the best predictor of gender conformity. If it were, why would we spend the amount of time, money, and education teaching our children how to be boys and girls and reinforcing gender conformity throughout our lifetime? New theories, as developed by Judith Lorber, in her article Believing is Seeing: Biology as Ideology, brilliantly captured an emerging sociological perspective. Turning conventional wisdom on its head, she argued that socially constructed gender difference may be as much the cause of our sexual/biological understanding of difference as its effect. The political implications were clear: we ideologically construct biology to make our gendered behavior seem natural. If gendered differences are made to appear irreversible (rooted in biology), that is, natural, it is easy to reinforce the status quo (read heterosexuality and male privilege) in our gendered relationships.
If we “believe” that it is biology that produces two—and only two—genders, we will not “see” beyond male and female. If, however, we believe that gender is flexible and fluid serving the cultural demands of societies at a particular time and in a particular place, we can envision gender differently. Lorber points to both African and American Indian communities where the social construction of biology yields more than two genders. There are “male-women” (biological males who behave, dress, work, and are treated as women) and there are “manly-hearted women” and/or “female-men” (biological females who work, marry, and parent as men). They self-identify and are socially recognized as a third gender. The nearest equivalency in our culture to these third-gender persons are those who self-identify and are socially recognized as transgendered people: people who identify with a gender that differs from their assigned sex at birth.
If we “believe” that it is biology that produces two—and only two—genders, we will not “see” beyond male and female.
Although Americans have become increasingly aware of and accepting of them, those who identify as transgender are far from treated equally by the cis (non-transgendered) population. The case of Christie Lee Cavazos is a good example. She filed a medical malpractice suit against the doctor whom she believed caused her husband’s untimely death (Littleton v. Prange 1999). What should have been a straightforward malpractice suit on behalf of her husband of 20 years took a different direction when the court chose to first examine the validity of her marriage as a transgender woman to a cis-gender man. Laurel Westbrook and Kristin Schilt  report that although Christie had undergone genital surgery, legally amended all of her government documents to categorize herself as female, had a legal marriage, and had medical experts who testified that she was, physically and psychologically, a woman, the judge ruled that she was and would always be a male because of her sex designation at birth. Therefore, she could not file a lawsuit as a spouse. Her sex at birth, more than her socially constructed and legally accepted status as a woman, determined her gender.
As a nation we acknowledge basic civil rights for transgender individuals. Still, despite evidence that biology counts for little, such determinations remain key in determining gender, especially in gender-segregated settings such as public restrooms. The current brouhaha over trans women entering women’s spaces suggests that once again anatomy is key in determining gender identity. This is especially clear because there appears to be little if any anxiety about trans men in men’s spaces. Or as Schilt and Westbrook put it, the conflict is less about gender than it is about bodies; mainly the presence or absence of a penis. This argument is supported by the fact that there is no conclusive evidence that either rape or aggression are unequivocally or necessarily attached to levels of hormones or anatomy, that is, to males. It may be more associated with those who identify strongly with socially constructed concepts of masculinity and male prerogative.
The nondiscrimination law conflict is less about gender than it is about bodies; mainly the presence or absence of a penis.
Believing is seeing. Biological assumptions that there are two and only two sexes and consequently only two genders work to maintain the status quo. It is not surprising that we have returned to biological determinants of gendered behavior at the very same time that the balance of power and privilege between men and women has come in for a leveling (some refer to this as the last gasps of patriarchy). Constructions of what is “natural” to men and women can be manipulated for political ends making it difficult to “see” beyond our current social constructions of gender.
 Doing Gender, Determining Gender: Transgender People, Gender Panics and the Maintenance of the Sex/Gender/Sexuality System Laurel Westbrook and Kristen Schilt, Gender & Society (2014) pp. 28- 32.