The Science of Gender

Are there two? No, more than four.

Human sexuality is a complicated biological affair. There are two time periods that matter, in utero and at puberty, and two forms of biological growth that are influential, and biological organizational and activational aspects. These interact to influence post-puberty sexuality. Moreover, brain circuits and body appearance are influenced separately. Brain circuits and body appearance are actual separable outcomes. As a result, the brain may be oriented towards one gender and the body may appear as the other gender.

You might conclude that there are four genders then:

• Female brain-female body

• Male brain-male body

These first two are what those ignorant of biological factors assume is species normal. But there are also these genders:

• Female brain-male body

• Male brain-female body

The last two are challenging to those who are stuck in either/or categories or to cultures that have rigid categories for humanness. But they are also challenging to the individual themselves, and to their family, because they may take a while to figure out their brain imprinting, which emerges more clearly, typically, during puberty.

In actuality, it is more complicated. Within these four categories there are ranges of strength in one direction or another. There are gradients and some people end up being in the middle—bisexually oriented.

Sexuality begins in the womb. At the beginning, the embryo emerges with an XX or XY chromosome pattern. During fetal organization, there are hormonal patterns that expose the fetus to an imprint of maleness or femaleness separately on brain circuits and on bodily appearance. Each induces particular hormonal releases that continue the development of gender in the womb and after. These imprints are later ‘developed’ during puberty, activating the proclivities established in utero. But it’s complicated. Read on.

Regarding Male Body and Brain Development

World renown neuroscientist, Jaak Panksepp (1998) explains male brain and body development:

“What the Y chromosome provides for the male is testis determining factor (TDF), which ultimately induces the male gonadal system to manufacture testosterone…The actual manner in which male brain and body development proceeds is determined by the timing and intensity of the resulting hormonal organization signals, namely, testosterone and two closely related metabolic products, estrogen and dihydrotestosterone (DHT). These last two steroid hormones normally control the final trajectory of brain and body development, respectively, while the XY baby is still in the womb—still hidden from the cultural influences of its future social world…After the TDF gene has induced the male fetus to manufacture testosterone, several critical events must take place before the male brain and body phenotypes can be fully expressed. First, testosterone needs to be converted in two distinct one-step reactions to estrogen and DHT. The final organizational signal that tells the brain to masculinize is estrogen, and the signal that tells the body to develop along male-typical lines is DHT.” (p. 232)

There are additional products of testosterone metabolism that dictate whether the male path will be maintained before and after puberty. If “errors” occur in the biochemical processes along the way, various forms of homosexuality will result.

Regarding Female Body and Brain Development

“The XX sex chromosome pattern informs the female body to manufacture proteins such as the steroid-binding factor alpha-fetoprotein, which can thwart the cross-gender organization influences of sex steroids during early development. This protects the female fetus from being masculinized by the generally higher levels of maternal estrogens. If there is not enough of this fail-safe factor, or if the maternal levels of estrogens are so high that they saturate the available alpha-fetoprotein, the females will proceed toward a male pattern of development—sometimes in both body and mind, sometimes in one but not the other, depending on the hormonal details that have transpired.” (p. 232).

Because of the complications of biochemistry and environmental effects, some children may appear to be female at birth but at puberty develop a masculine body and brain (“guevedoces;” Imperato-McGinley et al., 1979). Among humans, there are other genetically based differences, such as those born with an extra chromosome (XXY or XYY).

What other developmental influences affect gender development?

Most studies of gender and sexuality development have been done with rats, whose brain and development are largely comparable to humans. Research studies indicate that maternal stress during pregnancy is more likely to result in homosexual male offspring (Ward, 1984). There is corresponding evidence from comparing German males born before and after World War II with those born during the war time, finding more homosexuality during the stressful time (Dorner et al., 1980). Males are more likely to be homosexual the more older brothers (including miscarriages) they have due to biochemical antibodies in the womb (Balthazart, 2018).

Not surprisingly due to the amount of stress pregnant women experience these days in an unnested society, the number of non-heterosexuals in the USA keeps rising. There are approximately 9 million self-identified LGBT (lesbian, gay, bisexual, transgender) individuals in the USA.

What societal factors influence gender development?

The USA has poured thousands of untested chemicals into its food, water and consumer goods, causing all sorts of health problems (Davis, 2009). Some of these chemicals are endocrine disrupters that mess up sexual development physiologically and psychologically (Hood, 2005; Rich et al., 2016).

At the same time, the attention to gender identity across media has increased interest and perhaps induced not only gender dysphoria but pharmaceutical gender exploration, creating challenges for medical professionals (Kaltiala-Heino et al., 2018; Newsroom, 2023).

What is ‘natural?’

Although Nature has a tendency to create clear cut sexuality (male brain-male body; female brain-female body), this does not always happen. Same-sex sexual behavior has been documented in over 1500 non-human species (Gómez et al., 2023).

Native American groups have long understood that there are “two-spirit” people, those outside the male-female duality, and welcomed their gifts. In some cases they were keepers of cultural traditions (Smithers, 2022). Unlike the European conquistadors and settler-colonialists, First Nation/Indigenous communities allow individuals to grow their unique spirits instead of controlling and coercing them into pre-established categories. They honor Nature as wiser than they. Ah, nestedness!

Nature has created a rainbow spectrum of sexuality. Can we stop ourselves from messing it up?

References

Balthazart, Jacques (2018). "Fraternal birth order effect on sexual orientation explained". Proceedings of the National Academy of Sciences of the United States of America. 115 (2): 234–236

Blanchard, R., Bogaert, A.F. (1996). Homosexuality in men and number of older brothers. American Journal of Psychiatry 153, 27–31.

Dorner, G. et al., (1980). Prenatal stress as possible aetiogenetic factor homosexuality in human males. Endokronologie 75, 365-368.

Gómez, J.M., Gónzalez-Megías, A. & Verdú, M. The evolution of same-sex sexual behaviour in mammals. Nat Commun 14, 5719 (2023). https://doi.org/10.1038/s41467-023-41290-x

Hood, E. (2005). Are EDCs blurring issues of gender? Environmental Health Perspectives, 113(10), A670-677. doi: 10.1289/ehp.113-a670

Imperato-McGinley et al. (1979). Androgens and the evolution of male-gender identity among male pseudohermaphrodites with 5-alpha-reductase deficiency. New England Journal of Medicine, 300, 1233-1237.

Kaltiala-Heino, R., Bergman, H., Työläjärvi, M., & Frisén, L. (2018). Gender dysphoria in adolescence: current perspectives. Adolescent Health, Medicine and Therapeutics, 9, 31-41, DOI: 10.2147/AHMT.S135432

Newsroom (2023). Gender dysphoria in young people is rising—and so is professional disagreement. British Medical Journal, February 2. doi: 10.1136/bmj.p382

Panksepp, J. (1998). Affective neuroscience: The foundations of human and animal emotions. New York: Oxford University Press.

Rich, A.L., Phipps, L.M., Tiwari, S., Rudraraju, H., & Dokpesi, P.O. (2016). The increasing prevalence in intersex variation from toxicological dysregulation in fetal reproductive tissue differentiation and development by endocrine-disrupting chemicals. Environmental Health Insights, 10. doi:10.4137/EHI.S39825

Smithers, G.D. (2022). Reclaiming two-spirits: Sexuality, spiritual renewal & sovereignty in Native America. Beacon Press.

Ward, I.L. (1984). The prenatal stress syndrome: Current status. Psychoneuroendocrinology, 9, 3-11.