Mammalian Sex is Binary

The Harvard Crimson writes:

“There are only two sexes.” ...

The argument goes as follows: “Trans people can ask to be called whatever they want, but they can’t change the fact that there are only two sexes.”

The idea that sex is binary is presented as an irrefutable fact of life, the most natural truth in the world. Anyone who dares question this “fact” is quickly discounted as a “radical, woke ideologue” or an agent of the “liberal DEI agenda.”

That is correct.

It was not until the 18th century that a binary model for sex became prevalent in Western society, and at the time it was deeply connected to eugenics and scientific racism.

The sex binary is a human invention — one that is driven, at least in part, by political motives.

Wow, literature has written about sex differences for millennia, but Harvard thinks they were discovered in the 18th century!

First, it is bad science. Treating the sex binary as an immutable fact ignores the ample evidence that calls it into question, producing biased research design and results.

Peer-reviewed research contradicts a strictly binary interpretation of sex. We have yet to uncover a precise causal mechanism that definitively and consistently guarantees an individual’s sex.

No, Wikipedia explains the causal mechanism:

Sex-determining region Y protein (SRY), or testis-determining factor (TDF), is a DNA-binding protein (also known as gene-regulatory protein/transcription factor) encoded by the SRY gene that is responsible for the initiation of male sex determination in therian mammals (placental mammals and marsupials).[5] SRY is an intronless sex-determining gene on the Y chromosome.

The usual biology definition is that males have small gametes, and females have large gametes. The SRY gene is the cause. So males can be defined as those with a functioning SRY gene.

Is this definitive for all purposes? Apparently not.

under a system implemented by the International Olympic Committee in 1992. Athletes with an SRY gene were not permitted to participate as females, although all athletes in whom this was "detected" at the 1996 Summer Olympics were ruled false positives and were not disqualified. Specifically, eight female participants (out of a total of 3387) at these games were found to have the SRY gene. However, after further investigation of their genetic conditions, all these athletes were verified as female and allowed to compete. These athletes were found to have either partial or full androgen insensitivity, despite having an SRY gene, making them phenotypically female.

Okay, but the reason for this controversy is mainly from transgendered people who do not like being identified by their genes. They want to choose their gender. They have persuaded everyone to adopt a sex-gender distinction, to emphasize that gender is mutable.