1/ Thread on definitions.
Succinct definitions are difficult in biology, because biology is complex and many categories have fuzzy boundaries. Defining biological sex is no different in this regard. Below is the definition @FondOfBeetles and I presented in our @WSJ essay.
Succinct definitions are difficult in biology, because biology is complex and many categories have fuzzy boundaries. Defining biological sex is no different in this regard. Below is the definition @FondOfBeetles and I presented in our @WSJ essay.
2/ Definitions can be neat and sleek as a concept, but are less tidy when applying them to the real world. Take the broad definition of "male" and "female" for instance.
In the broadest sense, males produce small gametes (sperm), and females produce larger gametes (ova).
In the broadest sense, males produce small gametes (sperm), and females produce larger gametes (ova).
3/ Seems clear enough, right? The gulf between sperm and ova is vast and unbridgeable! Yes, that is true. If you produce sperm, you're a male, and if you produce ova, you're a female.
But this definition breaks down a bit when we are tasked with sexing flesh & blood individuals.
But this definition breaks down a bit when we are tasked with sexing flesh & blood individuals.
4/ What do I mean? Well, adolescents & postmenopausal women don't produce gametes. And some individuals, for whatever reason, are born infertile. Must we then conclude all these individuals therefore have no biological sex?
No. They do, but we need a more practical definition.
No. They do, but we need a more practical definition.
5/ So what's THE definition of biological sex for actual people? I don't think that's the right question to ask. Instead, we should ask what's THE BEST definition of biological sex that reflects the essence of the broad definition above and be generalizable to other species.
6/ Biological sex must relate primarily to reproduction, and thus must be concerned with PRIMARY reproductive anatomy. What cannot be included in the definition of sex are superfluous traits that can vary independently between the sexes.
7/ Many try to suggest traits like chromosomes, neuroanatomy, hormone profile, etc., should be included in the definition of biological sex. This makes no sense, because these traits can all vary between the sexes, yet do not change an individuals biological sex.
8/ For instance, I am a typical biological male. I've never been karyotyped, but if I discovered I had XX chromosomes I wouldn't suddenly become female. Likewise, there is no brain state or hormone profile I could wake up possessing that would change my sex from male to female.
9/ Furthermore, defining sex using these traits are not generalizable to other anisogametic species. Many reptiles, for instance, develop into males or females depending on the temperature at which they are incubated instead of chromosomes.
10/ Likewise, plants don't have brains, so defining sex based on neuroanatomical traits makes absolutely no sense here.
So what do actual males and females of reptiles, plants, humans, and all other anisogametic species have in common?
So what do actual males and females of reptiles, plants, humans, and all other anisogametic species have in common?
11/ They all have all developed one of two distinct types of reproductive anatomy that develop for the production of small or large sex cells—sperm and eggs, respectively—and associated biological functions in sexual reproduction.
12/ Yes, this definition isn't 100% perfect. No definition of categories with fuzzy borders will ever be perfect. But we can't let the perfect be the enemy of the good & useful. If you want to argue against our definition, it is not sufficient to simply point at the fuzzy border.
13/ Anyone can point out flaws, but it's much more difficult to come up with better alternatives. If you don't like the definition, then you need to propose another definition & DEFEND it on the grounds that it is more useful and/or generalizable than the one you're criticizing.
