Science

In humans, as in most animals or plants, an organism’s biological sex corresponds to one of two distinct types of reproductive anatomy that develop for the production of either small or large sex cells – sperm or eggs.

This differentiation evolved over a billion years ago. It is the reproductive strategy of all higher animals and plants, including the mammalian class to which humans belong. Understanding this is critical to biology and medicine.

Sex is determined at conception: the presence of a Y chromosome initiates not just hormonal cascades, but other developmental cascades which result in sex differences. Having two X chromosomes also has distinct effects on development. Sex differences exist at the chromosomal, genetic, hormonal, anatomical, physiological, and behavioural levels. Many of these differences are understood, and many remain to be studied.

What is the problem?

There is a dangerous and anti-scientific trend towards the denial of biological sex, even in science. Highly esteemed scientific periodicals are now running articles undermining the observable reality of biological sex. For example an article in Scientific American in 2018 argued “Biologists now think there is a larger spectrum than just binary female and male”. In 2018 an editorial in Nature stated: “The research and medical community now sees sex as more complex than male and female.”

Arguments are made that because there are rare developmental conditions associated with anomalous chromosomal combinations or resulting in ambiguous sex characteristics, the categories male and female exist on a “spectrum” or are simply “social constructs”. Such attempts to reframe sex as a social construct are harmful to scientific discourse and research, and to the ability to discuss the social implications of the reality of sex.

There are societal and legal questions about how best to accommodate people who do not feel comfortable with their sex, but addressing these do not require that we undermine scientific understanding or communication.