The Spectrum of Sex

Exploring the Flawed Binary

Writer: Luke Muschialli
Editor: Mahidhar Sai Lakkavaram (Mahi)
Artist: Eshka

The binary of sex has formed the basis of societies around the world for centuries. Over recent years, as society has begun to acknowledge the damaging effects of social classification surrounding sexuality and gender, many have found comfort in the seemingly defined categories of man and woman; testosterone and oestrogen; XX and XY. However, this classification system is undeniably flawed. As we dig deeper into what it means to be biologically a “man” or a “woman,” the system breaks down, and with it the scientific justification for two biological sexes dissipates. Through investigating three established classifciation systems of biological sex (chromosomes, reproductive anatomy, and hormonal profile) and discussing their limitations, we will determine what science really says about biological sex and why it is important that we are vocal about this field of research.

In the past, it was widely accepted as a conclusive, scientific binary that an individual with XX chromosomes is “female” and one with XY is “male.” This is not the case. Human sex chromosomes have been shown to have just as much inter-individual variety as their  autosomal counterparts. Historically, the incidence of XXY individuals assigned male at birth (AMAB), or XXX individuals assigned female at birth (AFAB), or even XO AFAB was documented, but considered so rare that it was dismissed. In truth, if a karyotype (full chromosome screening) were to be performed on all of us, the results would reveal anything but a binary system. It is estimated that the incidence of XXX females is as high as 1/1,000 live births and the the incidence of XXY males is estimated to be even higher at 1/600 live births. The concept of sex chromosomes mosaicism has also been described, in which some of the individual’s cells express XX chromosomes, and some XY. Clearly the science of sex chromosomes isn’t quite as binary as we once thought. 

Although karyotyping is an effective way to gain an insight into a person’s sex, it is very rare that this is used in day-to-day life. Rather, it is usually a person’s reproductive anatomy that would be used to assign sex. However, as it has been known for centuries, this is not a straightforward task. Numerous societies have written about intersex individuals. Khunthā are mentioned in Islamic texts as people who have ambiguous reproductive anatomy and the Native American population widely accepted intersex individuals within society. Even in 1 BCE, Siculus, a Greek historian, wrote of individuals who were born with ambiguous genitalia, describing them as prodiges. We now understand that up to 25 genes are responsible for coding our sexual characteristics and mutations in any of these can lead to ambiguous reproductive anatomy. It has also become clear that our chromosomal makeup is not always connected to our reproductive anatomy. Approximately 1/25,000 AMABs have XX chromosomes, but present with classically male external reproductive anatomy. It is clear that a binary does not exist here and that reproductive anatomy should also be seen as a spectrum.

Hormones are an important topic in this field as well, as they are often used to categorise people into the binary of sex. An important example of this is in sports, where the level of testosterone is used to determine if an individual is assigned to the male or female category. The International Association of Athletics Federation (IAAF) specifies that in order to compete in the female category, individuals must have a serum testosterone of < 5 nmol/L. This was introduced as the binaries of reproductive anatomy and chromosomal makeup would not suffice,  already bringing into question the viability of a sex binary. This division has actually strengthened the argument against the binary of sex; although it was imposed as a seemingly definitive cut off, there are numerous case studies of athletes being excluded from “their” category because of it. Mokgadi Caster Semenya was banned from international competition for a year due to having higher serum testosterone levels than this arbitrary cut-off, despite being AFAB and having identified as such throughout her life. Once again, we see an arbitrarily imposed binary rise and fall.

It is vital that the scientific community acknowledges this body of research. The continued stratification of the sexes under a false scientific pretence continues to be used to deny the existence of intersex individuals and to intensify discrimination against them. Whether we intend it to or not, the scientific world’s apathy towards this issue is the ammunition for the discrimination against the queer community. Numerous pieces of legislation limiting the freedom of intersex and gender non-conforming individuals around the world continue to be passed, which is a consequence of the lack of understanding about the spectrum of sex. We have the peer-reviewed evidence to counteract this, but due to continued discrimination and prejudice both within and outside of the scientific community, this has not gained traction. 

This article does not intend to suggest the scientific community call for a dismantling of the biological sex structures that permeate all aspects of society. Rather, we need to use the data we have gathered to emphasise that sex is a spectrum and to facilitate a greater understanding of, and acceptance towards, individuals who do not fit into this flawed binary that society has constructed. As a scientific community, we need to be more fact-oriented, empathetic, and empowering. Nature doesn’t create binaries, and neither should we.

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