Biology is entirely responsible for gender identity. This is being supported more and more by scientific evidence. With regard to biology, there is increasing evidence that hormonal effects on fetal development play a significant role in development of gender identity.

Melissa Hines postulated three models of action of hormonal influences on gender in 2002:

“The Classic Model of hormonal influences states that presence of testicular hormones (testosterone) during early fetal life causes a masculine development of rodents, while absence of testicular hormones causes a feminine development.

The Gradient Model describes a more gradual effect of hormonal influences on behavior. Normal variations in hormones cause movement along a male and female gradient within each sex. Therein we assume that a greater amount of hormones administered in animal tests, creates a more dramatic change in behavior.

The Model of Active Feminization Theory postulates that ovarian hormones are, opposed to the previous mentioned models, needed to induce, in some degree, the female sexual differentiation. It is thought that ovarian hormones cause a lesser, but present effect of mild virilization to some brain areas.”1

Biology is also seemingly implied in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Text Revision (DSM-IV-TR) as gender identity disorder “..represents a profound disturbance of the individual’s sense of identity with regard to maleness or femaleness.”2 (emphasis added)

My thesis is also supported by personal experience. I am a transsexual, and I know my identity is inherent. I was born and raised in the rural South in the 1970’s. Being an effeminate boy was unheard of in that culture. I tried very hard to conform, but I was still subjected to ridicule and bullying. While I attempted to fit in by adjusting my outward gender expression, my internal and inherent gender identity was ultimately betraying me.

Based on some of the articles written supporting societies’ role in forming gender identity, I think there is some confusion between gender identity and gender expression. The two are distinct, yet easily confused.

Gender identity is inherent and internalized. It is impossible to determine an individual’s gender identity by their appearance. If the individual has a gender identity that is incongruent with their physiological sex, they may not have come to terms with that and might still be presenting themselves as the gender that does match their physiological sex. I did that for thirty-six years. Gender identity is entirely about how the individual personally (and honestly) identifies or classifies themselves.

Gender expression, however, is how one presents gender externally. Dress, mannerisms and speech are key indicators. Much of what is acceptable for gender expression is a societal construct. There are countless unwritten rules regarding what is acceptable for a masculine or feminine gender expression. In the modern western world, we live in a society that largely recognizes only two genders. For those interested in getting a more comprehensive and eye-opening view of gender expression, roles, and identity, I recommend the book “Gender Outlaw” by Kate Bornstein3.

Based on the research, the evidence, and my own personal experience gender identity is a biological phenomena. Gender expression, by contrast, is largely a societal construct and the means by which we express (or suppress) our inherent gender identity.

1) Hines M, “Sexual Differentiation of Human Brain and Behavior”. Hormones, Brain and Behavior. Vol. 4. 2002: Elsevier Science (USA). Pp. 425-461.

2) American Psychiatric Association, “Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Text Revision”. Jaypee 2000. p. 580

3) Bornstein K, “Gender Outlaw on Men Women, and the Rest of Us” Routledge 1994