Biological sex can be defined by karyotype and the ability to bear children, but these criteria may not be sufficient. Photo credit: Tim Mossholder via Unsplash
Define a woman. Spoiler: there’s no obvious answer when it comes to biological sex
Set the scene. Swarms of journalists packed into creaky, dark plastic chairs. Camera flashes mingling with lightning-quick questions. A caffeine buzz and the anticipation of a story. Lord Hodge, his suit crisp, begins to read. His words dictate a Supreme Court ruling. His words disappoint. The Supreme Court has decided that “women” are defined as those born biologically female.
The belief that women and men are biologically distinct, immutably one or the other, has made quite the comeback.
The question of what exactly defines a “woman” is not unique to the Supreme Court; neither is the sentiment that womanhood is something innate, something biological. The West seems to be confronted with a growing rise in gender essentialism. The belief that women and men are biologically distinct, immutably one or the other, has made quite the comeback.
In fact, similar rhetoric seems to be echoed more candidly across the pond. In 2022, Republicans in the Congress sought to propose the “Women’s Bill of Rights,” arguing that defining womanhood by way of biological sex was necessary to engender sex-based protections in vulnerable spaces like healthcare and shelters.
‘Females are the sex that have the capacity to bear children and produce eggs,’ Representative Diana Harshbarger argued, ‘Women have two X chromosomes and are born with a uterus and ovaries.’ Senator Jim Banks of Indiana co-sponsored the resolution, arguing that it was ‘pointing out obvious truth about biological sex.’ It seems that politicians are imbued with the distinct sense that biological sex is a binary. Whether you’re biologically a man or woman is easy to tell, easy to understand, and easy to claim. They’re laughably wrong.
It’s useful to understand why every aspect of Rep. Harshbarger’s seemingly simple definition is far more contentious than it appears to be. First, she defines women as individuals with XX chromosomes, implying that men are individuals with XY chromosomes. Indeed, the SRY gene present on the Y chromosome codes for the testis-determining factor (TDF), which, in turn, activates various genes related to testicular development and testosterone production. Testosterone controls many of the secondary sex characteristics we describe as conventionally male—greater height, a deeper voice, an enlarged Adam’s apple. In women, the SRY gene is often absent due to their XX makeup. In its absence, testicular development does not occur, and a female developmental pathway takes place.
While superficially sensible, chromosomal sex is not the end all be all. Take Swyer Syndrome. In this rare condition, an individual’s karyotype—their chromosomal makeup—is XY, but the SRY gene either does not work or is not present. Despite their XY makeup, Swyer Syndrome patients often possess female external genitalia (vulva) and internal reproductive structures like Fallopian tubes and a uterus. In lieu of ovaries or testes, streak gonads (scar tissue prone to forming cancer) are present. Patients are usually perceived from birth to be female, despite being karyotypically male. A similar phenomenon can be observed in patients with Complete Androgen Insensitivity Syndrome (CAIS). XY individuals possess the SRY gene, testicular development occurs, and testosterone is produced. However, the receptor for testosterone is non-functional. Internal male reproductive structures like the vas deferens (sperm duct) and external reproductive structures like the penis both need testosterone signalling to form. As the testosterone receptor is non-functional, the body is completely unable to respond to testosterone. Thus, despite being karyotypically male and even having the SRY gene, female reproductive structures (vagina, uterus, Fallopian tubes) form along with a hyper-feminised appearance. The chromosomal definition of womanhood, thus, falls apart upon closer inspection – the SRY gene is only one of many controlling the development of male characteristics. It is one step in the long and complex signaling pathways that control sex determination, albeit an important step. Therefore, it is arbitrary to base our entire understanding of sex on chromosomes, when individuals can possess the SRY gene and appear as female despite being karyotypically male.
The chromosomal definition of womanhood, thus, falls apart upon closer inspection – the SRY gene is only one of many controlling the development of male characteristics.
Another part of Rep. Harshbarger’s definition relies on the presence of two specific female internal reproductive tract structures, the uterus and the ovaries, to determine sex. This selection is arbitrary – what makes the uterus a more intrinsically female structure than, say, the Fallopian tubes? Or the cervix? Nevertheless, even this criterion bears more nuance than the binary framing seems to suggest. For instance, patients with Persistent Mullerian Duct Syndrome(PMDS) possess mutations in the gene for AMH, a hormone that normally prevents female structures from developing. As this hormone is non-functional, karyotypically XY males develop the uterus, Fallopian tubes, and cervix, the development typical in females. Patients with PMDS also have the internal and external genitalia typical of males, and appear, externally, as male. Does the presence of a uterus confer these individuals with status as women? The uterus and ovaries are important structures for female sexual development. They are also only two structures among many. It seems reductive to base womanhood on the presence of two organs within a larger reproductive system, when sex depends on complex spatial and temporal phenomena.
Reducing the female trait to a specific capability, one that a ridiculously large number of women are unable to carry out, seems to make one lose faith in the definition itself.
Thirdly, Rep. Harshbarger’s Bill seeks to define women based on their ability to produce children. This, obviously, heralds a serious problem. Women, unlike men, are born with a set number of eggs that they can produce throughout their lives. This number is determined during embryological development. After these eggs are exhausted, women undergo various hormonal and physical changes referred to as menopause. During menopause, their oestrogen levels drop, and they become infertile. Are menopausal women, who have lived decades of their lives as women, no longer conferred the trappings of femaleness simply because of their infertility? This definition also ignores women with conditions like polyendocrine metabolic ovarian syndrome (PMOS, previously known as PCOS), which affects 10-13% of all women of reproductive age. Women with PMOS are unable to ovulate frequently and produce mature eggs, causing trouble with conception. Endometriosis, too, occurs due to the invasion of the uterine lining into other tissues like the ovaries, affecting another 10% of women worldwide. Again, due to the delays in ovulation caused by the condition, about 30-50% of women with endometriosis are infertile. This begs the question – if a definition excludes a large portion of individuals who identify as women, is it necessarily a good one? In fact, it seems that this definition of being a woman excludes Rep. Diana Harshbarger herself, who, at the age of 66, is almost certainly either menopausal or post-menopausal and, therefore, unable to give birth. Reducing the female trait to a specific capability, one that a ridiculously large number of women are unable to carry out, seems to make one lose faith in the definition itself.
Lastly, the definition offered to eager reporters and disappointed transgender people alike by the Supreme Court confers the responsibility for sex determination to doctors, citing that those with female listed on their birth certificate are the only ones that are ‘biologically woman.’ Sex at birth is usually determined by external genitalia and listed on an individual’s birth certificate. It seems deceptively simple – a penis indicates a man and a vulva indicates a woman. Where this logic falls apart is in the case of ambiguous genitalia. For one, the clitoris and penis both develop from the same ambigenderous gentile tubercle. Though they undergo different developmental pathways, a chromosomal female with exposure to excess male hormones (such as testosterone or its derivative dihydrotestosterone) can produce an enlarged clitoris and fused labia, giving the appearance of a small penis or scrotum.
An example of this presents itself in congenital adrenal hyperplasia (CAH), wherein the adrenal glands produce excess testosterone, causing female genitalia to appear male. Individuals may have ovaries, a uterus, the ability to produce eggs, and also a fully formed penis. Often, despite having female reproductive tract structures and fitting Rep. Harshbarger’s definition, infants with such CAH are determined to be male at birth. This raises the question of whether using external genitalia, though easy and oftentimes effective, is the most accurate and precise way to determine sex. When so many cases fall between the cracks of the binary established by the system, it goes to show that the system itself bears significant flaws.
As legislators and courts push for single-sex spaces, they ignore the reality that sex is not a binary, but a bimodal spectrum.
As legislators and courts push for single-sex spaces, they ignore the reality that sex is not a binary, but a bimodal spectrum, including various individuals who fall into the umbrella category of ‘intersex’. Beyond the intricacies of biological sex, an individual’s gender identity may also be nuanced and complex. The policies and rulings discussed in this article neglect this complexity and adversely affect such individuals. Recognising this nuance, thus, can make all the difference. It can affect your cousin who just wants to swim with her friends. It can affect your friend who needs to access a women’s shelter. It can affect the child just trying to access much-needed medical care. And as these conditions may only be discovered in adulthood, it can affect you.
Some ideas expressed in this article are opinion, and may not represent the opinion of The Oxford Scientist as a whole.
Edited by Mia Clark-Webb, Mathilda Lang, and Sophie Lyne.
