“Is the baby a boy or a girl?” is often the first question of new parents.
“I will get back to you about that,” is not the answer a couple expect to hear. But ambiguity in sexual anatomy, where an infant appears neither clearly male or female, does occur.
In these last 50 years, scientists have learned that the development of both our gender and our sexual identity is a complex process. There are many factors involved including chromosomes, sexual anatomy, levels of hormones, and brain development. For some individuals, these do not all align as clearly “male” or “female.”
Working at Johns Hopkins University Psychohormonal Unit beginning in 1951, Dr. John Money was the specialist who first clarified this complex system.
All of us have the same undifferentiated gonadal tissue for the first 6-7 weeks. The first factor is the presence of either XY or XX chromosomes. A gene on Y-chromosome (SRY) causes gonadal tissue to become testes. Without the SRY, the gonads develop into ovaries. All of us have two sets of tubes alongside the gonads. If testes develop, the Wolffian tubes develop into vas deferens.
If ovaries develop, the Mullerian tubes develop into oviducts. However, sometimes an XY child can lack the SRY gene and be female. Or an XX child can carry the SRY and be male. Or an XY child may have external female anatomy but have internal testes—her body cells failing to recognize the circulating testosterone and therefore developing female.
In addition, our hormone levels vary. Although textbooks simplify that males-have-testosterone and females-have-estrogens, everyone produces both. In males, the small levels of estrogens mainly come from fat tissue. Females receive small amounts of testosterone come from adrenal glands. But humans vary in the enzymes that produce these hormones. We observe the resulting variations in body growth, voice, hair growth, and other traits in the people around us.
In his clinical study of cases where differentiation failed to work correctly, Money noticed that masculine and feminine behavioral roles did not always match with who they were sexually attracted to. In 1955, Money borrowed the grammar term “gender” to indicate a person’s self-awareness as fitting the male or female role. He describes: “Gender role is everything that a person says and does to indicate to others or to the self the degree that one is either male or female, or ambivalent; it includes but is not restricted to sexual arousal and response.”
Therefore a person could be effeminate but not attracted to men, or masculine but not attracted to women.
Money knew that when children developed a sense of self awareness between ages 4 and 6, a few wanted to be the “other” sex. But did brain gender and sexual differences form before or after birth?
This last factor, the mental gender and sexual identity, was likely to be caused by the influence of hormones and other chemicals during brain development. John Money died in 2006 but another set of researchers were investigating brain cross sections for heterosexuals, transexuals, and homosexuals. The team of Professor Swaab in Amsterdam discovered that male-to-female transexuals had the brain structure (and gender identity) of females although their original anatomy was male. However, this brain region in male homosexuals matched regular males. Workers at three other institutes in America and Sweden accumulated evidence of other brain differences in homosexuals (sexual identity).
We now know that sexual anatomy develops in the first half of pregnancy. The distinct brain centers controlling gender and sexuality develop in the second half of pregnancy.
Bottom line? We do not choose our XY or XX chromosomes. We did not choose the anatomy we were born with. We do not choose to have higher or lower testosterone or estrogen levels. Nor did we choose to have the brain structures for gender and sexual identity that we were born with.
The vast majority of us should feel lucky that all of these complex biological factors match. But we should also understand with compassion when they do not. Taken together, gender and sexual identity ambiguity is more common than all cases of Down syndrome and cystic fibrosis combined.