Science doesn’t stay still. The purpose of the scientific method is to question what we already know, and to see whether there are better explanations to describe what we see and experience in the world around us. Two classic examples from physics: Albert Einstein creating a new framework for understanding space and time with his theory of relativity; and the double-slit experiment demonstrating that a photon can, and must, be thought of as both a particle and a wave. (Arguably, the latter just demonstrates that our mental models struggle with reality.)
Ditto in biology. We understand more about how our bodies work than we did 20, 40, 60 years ago. We’re able to tailor vaccines to tackle novel diseases in record times. The frontier moves, all the time.
Hence you’ll find people online who will solemnly tell you that while it used to be thought that there were just two sexes, male and female, there’s now “a scientific consensus” that “sex is a spectrum”. You will usually then get into a back and forth about what they mean by “sex” (sometimes it’s actually gender, which isn’t the same thing: sex is your body, gender is in your mind) and what they mean by “spectrum” (usually they mean continuum, i.e. an unbroken set). And when you ask for some evidence of this “consensus”, you’ll often be presented with a link to one of the following articles. They’re all misleading, or wrongly interpreted.
Binary, not bimodal
Before we tackle them, let’s be clear. Sex — biological sex — is emphatically not a spectrum. It’s not bimodal either. Human height is bimodal: there are two peaks, around average female height and average male height, and a spread of others below, between and above. But with sex, you’re either male or female: the fertilised egg proceeds down one of two pathways towards the destination where it will produce either small gametes (sperm, in humans) or big ones (ova, in humans). The union of those two different gametes is how humans reproduce. There’s no third sex, no ova-ova union or sperm-sperm union.
At which point people always say “what about intersex people? They’re a third sex/not part of the binary.” This is a misunderstanding, brought about by the word itself. People with intersex conditions are a subset of the larger group…