Five Tidbits of Science Regarding The Transgender Condition

The opponents of transgender equality tend to create their arguments without any sense of the actual science that has been done to figure out what causes these differences in gender identity. The science has actually come a long way towards proving a biological basis for the transgender identity. It is beyond clear that gender identity is not a choice nor a psychological disorder. Unfortunately, being armed with good science is often not enough in a world where alternate facts sway public opinion more than the truth. Nonetheless, here are five things we know about gender identity according to science.

  1. Brain structure in transgender people show remarkable differences when compared to non transgender people who were born with the same biological sex. There are multiple areas in brain structure where differences have been identified. The bed nucleus of the stria terminalis (BSTc) in transgender male to female people has been found to structurally resemble a biological female’s. Another study has shown that the thickness of the corpus callosum in transgender people more closely correlates to the sex they identify with. The studies done only used transgender brains that have not been influenced by cross sex hormones to eliminate the possibility that the brain changes were the result of the hormones.
  2. Studies have been done to test for auditory and olfactory differences in transgender people. It was found that transgender people’s scores on these tests clearly correlated with the sex with which they identified with. These studies were also conducted with transgender subjects prior to cross sex hormone therapy.
  3. Some groundbreaking experiments have shown in animal developmental that the behavior of animals can be modified to create opposite sex behaviors without altering the biological sex. These studies involved restricting hormones during development to simulate what we believe happens in the womb with human transgender development.
  4. In twin studies it was found that identical twins will more often have both twins being transgender compared to fraternal twins. This is significant because if genetically identical individuals show a trait more often than non identical copies, it suggests that there is a high probability that there may be a genetic connection. This could be exciting research as it begins to show a possible mechanism for the development of transgender people.
  5. The case of Bruce/Brenda/David Reimer is very significant when it comes to understanding that gender identity is wired and not chosen. David was born a boy named Bruce but due to an circumcision accident, his penis was burned off as an infant. The doctor (John Moody) advised the parents that the only way Bruce could lead a normal life was to undergo sex reassignment. After the procedure, the baby was renamed Brenda and raised as a girl. If gender identity is hard wired we would expect this child to identify as a male and this is exactly what happened. At 15 years of age, Brenda transitioned to David. Despite not knowing and being socialized as a female, Brenda still developed a male gender identity. This is definitely strong evidence that gender identity is not a social construct and is not a choice.

 

References:

Kruijver, F. P. M., Zhou, J., Pool, C. W., Hofman, M. A., Gooren, L. J. G., & Swaab, D. F. (2000). Male to-female transsexuals have female neuron numbers in a limbic nucleus. Journal of Clinical Endocrinology and Metabolism, 85, 2034–2041

Govier, E., Diamond, M., Wolowiec, T., & Slade, C. (2010). Dichotic listening, handedness, brain organization and transsexuality. International Journal of Transgenderism, 12, 144–154.

Phoenix, C. H., Goy, R. W., Gerall, A. A., & Young, W. C. (1959). Organizing action of prenatally administered testosterone propionate on the tissues mediating mating behavior in the female guinea pig. Endocrinology, 65, 369–382.

Heylens, G., De Cuypere, G., Zucker, K. J., Schelfaut, C., Elaut, E., Vanden Bossche, . . . T’Sjoen, G. (2012). Gender identity disorder in twins: A review of the case report literature. Journal of Sexual Medicine, 9, 751–757.

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