The Central Issue

There are a number of important issues that underlie the modern understanding of transgenderism and how society deals with it. These include causes of the condition, how we distinguish "male" from "female" and the nature of congenital intersex conditions in which the usual male-female "rules" are broken.


The causes of transgenderism are not fully understood. However there is growing evidence that the transgendered conditions is due to a person's nature rather than the nurture received early in life. The early environment of transgendered people are just as varied as the wider population. There are no significant causal links relating conditions of early environment, such as absent fathers, with the transgender condition. Instead biological conditions appear to hold the key to the later onset of the condition.
  • Pre-natal evidence. An important clue to its biological origin is given by a recent study of the ratio of finger lengths. The study found that in transwomen the ratio of the lengths of the second and fourth fingers is comparable to that of genetic women and higher than that of genetic males [1]. This ratio is known to be directly related to prenatal hormone exposure and so it appears that transwomen had a lower exposure to androgens as fetuses.

  • Other biological links. Other studies find brain physiology is related to the target gender in transgendered people. A study in 1995 examined the brains of many individuals including six transwomen [2]. The study found that a tiny part of the brain known as the central subdivision of the bed nucleus of the stria terminalis (BSTc) is larger in men than in women. They also found that the BSTc of the six transwomen was as small as that of women generally. It is not known if the size of the BSTc is altered by hormone therapy. Nevertheless, this study does provide evidence the brains of the transwomen appear to coincide with their conviction that they are women, at least after transitioning. A more-recent study measured the total brain and the hypothalamus volumes of transgendered people before and during hormonal therapy [3]. The study found that the brain volumes are changed by the hormone therapy towards the proportions of the targeted gender.

    [1] H.J. Schneider, J. Pickel, G.K. Stalla, Typical female 2nd-4th finger length (2D:4D) ratios in male-to-female transsexuals-possible implications for prenatal androgen exposure, International Society of Psychoneuroendocrinology 31 265-269 (2006).
    [2] J.N. Zhou, M.A. Hofman, L.J. Gooren and D.F.A. Swaab, Sex difference in the human brain and its relation to transsexuality, Nature 378, 68-70 (1995).
    [3] H.E. Hulshoff Pol, P.T. Cohen-Kettenis1, N.E.M Van Haren, J.S. Peper, R.G.H. Brans, W. Cahn, H.G. Schnack, L.J. Gooren and R.S. Kahn Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure, European Journal of Endocrinology 155 107-114 (2006)].

Indicators of "male" and "female"

There are three quite different properties that indicate if a person is male or female.
  • The sex chromosomes indicate whether a person is genetically male or female. Genetic males have XY chromosomes and genetic females have XX chromosomes.
  • The anatomical sex characteristics of the body are also used as an indicator. Anatomical males have male genitalia and anatomical females have female genitalia.
  • The gender identity of a person is also another indicator of whether the person is male or female.
Usually all three indicators are in agreement. For example, a person with XX chromosomes will usually have female genitalia and a female gender identity. However, this correspondence between the three indicators is not always the case. People with intersexuality can have ambiguous genitalia and genitalia that does not match their sex chromosomes.


There are a number of intersex conditions where the sex chromosome does not match the anatomical sex of the person. The following two illustrate how nature can sometimes deviate from the rule "XX=female, XY=male".
  • Androgen insensitivity syndrome - genetic XY with female anatomy
    Androgens is the generic name of the male hormones which includes testosterone. People with androgen insensitivity syndrome (AIS) are genetically male (with a XY chromosome) but have female genitalia and a feminine appearance. The insensitivity to androgens means that their body doesn't develop in a typically masculine way. AIS people have a vagina but lack a uterus and ovaries and they have undescended testes. A person with complete AIS typically identifies as female. She may be unaware of her AIS condition.
  • Congenital adrenal hyperplasia - genetic XX with male anatomy
    This condition is the like AIS but for genetic females (with a XX chromosome). It is a genetic disorder in which the adrenal glands produce a high level of masculinizing hormones instead of cortisone. Typically the person develops male characteristics including a deep voice and dense body hair and has male genitalia, although in some cases the genitalia is ambiguous.

Summing up the Central Issue

In intersexuality the genetic and anatomical male-female indicators disagree. This leaves intersexed people with the question of which social gender role they should follow. Ultimately, however, it is their inherent gender identity that is the deciding factor in the decision. It is only by following a role in accord with their gender identity can they hope to achieve contentment. The male-female ambiguity in intersexuality allows an intersexed person to justify either gender identity and thus living in either gender role. In cases where their anatomy is not in sufficient accord with their gender identity intersexed people are given the opportunity to make appropriate changes.

In people who are transgendered, the absence of anatomical abnormalities does not lesson the status of the person's gender identity as being central to deciding the appropriate social gender role. In this context, transgendered people are no different from people with intersexuality. It follows that transgendered people should also be given the option of altering their anatomy to match their identity.