Biology Professor Explains That Biological Sex Isn’t As Simple As It Sounds

In all likelihood, you’ve heard about the controversy that surrounded author J.K. Rowling last year and may have noticed that discussion continue in some circles to the present day.

As the BBC reported , this matter centered around tweets that saw critics accuse Rowling of making transphobic statements as well as supporting similar behavior in others. In response, she claimed to “speak the truth” about biological sex and accused her critics of trying to erase the very concept.

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As Scientific American reported , however, such rhetoric tends to assume that the way scientists understand biological sex involves a rigid and clear-cut female/male binary. Yet as this article outlines, research into everything from brain structure to chromosomal and hormonal development does not support this way of conceptualizing how people come to exist.

And as one biology professor took to Twitter to explain, “biological sex” is more difficult to define and involves more variables and factors than those claiming to fight against the erasure of this concept tend to assume it does.

In December of 2019, Rebecca R. Helm — a biologist and professor at the University of North Carolina Asheville — began her Twitter thread by discussing chromosomes.

After all, people commonly understand biological sex as being influenced by whether someone has two X chromosomes or an X and Y chromosome.

But not only does Helm point to this understanding as conflating “chromosomal sex” with “biological sex,” but it assigns more biological influence to the Y chromosome at large than it really deserves. As she mentions, there’s just one protein found on that chromosome that activates genes associated with being male.

And while that distinction may sound pedantic, it’s actually important to note because there’s no guarantee that protein will stay attached to the Y chromosome.

Under such circumstances, Helm identified it as possible for a person to have contradictory markers for chromosomal, physical, and genetic sex.

But as she goes on to outline, even stopping at this complication would oversimplify the concept of “biological sex” because the factors that influence a person’s sexual development don’t stop at chromosomes.

Helm explained that hormone production also plays a role in how a person’s sex develops.

And as she discussed here, a person’s hormone production doesn’t always line up with their chromosomal or genetic sex — and again, these two outcomes don’t necessarily line up with each other, either.

Furthermore, if a person’s hormone production is particularly muted, they can be hormonally and physically non-binary regardless of their genetic or chromosomal makeup.

And as she goes on to outline, ignoring both chromsomes and hormones in favor of breaking people down to the cellular level doesn’t yield a simple definition of “biological sex” either.

For one thing, their role in biological sex depends on their responses to signals from sex hormones.

And since they vary in how capable they are of receiving those signals, they can introduce some variance in how a person’s physical sex lines up with their chromosomal, genetic, and hormonal sex.

Helm went through all of this to express that if a person’s “biological sex” can be defined, it’s as a myriad of potential combinations of chromosomal, genetic, hormonal and cellular materials.

And since those materials are capable of contradicting each other and even themselves to some extent, it’s hard to see how criticisms of transphobia do anything to “erase” the concept of biological sex when it’s already a nebulous concept depending on many unpredictable factors.

Helm also anticipated that some would argue that however miraculously people came to be this way, most people are either male or female.

However, that’s not something we can realistically know for certain in light of what we’ve already discussed.

In Helm’s experience, it’s not unheard of for her students to discover that their physical sex doesn’t line up with their chromosomal sex while they’re in her class. And since it can be difficult not to be distracted by questions of that means for them while they’re trying to do assignments, she avoids class activities that have them do that.

Without drilling down into the various complicated and interrelated internal processes that influenced every person on the planet’s development, it’s not really feasible to determine how common each of these combinations are compared to others.

Ultimately, her point is that while it’s already difficult to justify judging people for their gender identity, the foundation that some may feel they have for doing so isn’t as solid as they think.

After all, it’s not as though most people are abreast of all of their own chromosomal, genetic, hormonal, and cellular data. We’re all navigating our own ways to be comfortable in the complex genetic and chemical soup that is the human body.

As Helm put it, “Biology is complicated. Kindness and respect don’t have to be.”