What the heck is sex? A shockingly large number of people don’t actually know. They tend to think it’s something to do with chromosomes, or maybe body parts... hormones, possibly? I am afraid that all of that is a misunderstanding.
Sex is a system in which organisms reproduce by the combining of sex cells, called gametes. There are two types of gametes: large gametes called eggs (ovules in plants), and small gametes called spermatozoa or sperm (pollen in plants). Individuals of a species that produce large gametes are called females, and individuals of a species that produces small gametes are called males.
That’s it! It’s that simple. Nothing to do with chromosomes, genitals, or hormones. To quote the late Cambridge geneticist and evolutionary biologist Michael Majerus, “the fundamental distinction between males and females depends purely on gamete size. No other difference between males and females is universally definitive.”
Let’s look at some examples to hammer the point home.
Some plants like asparagus or juniper bushes are individually male or female. They don’t have penises or uteruses, or various levels of testosterone or estrogen. So how do we know which ones are male and which ones are female? The males produce small gametes, and the females produce large gametes.
Seahorses are a rare example of an animal in which the male gives birth. But how do we know that the males gestate and give birth? Because male seahorses produce small gametes, and the females produce large gametes.
Clownfish are known to change sex in a single sex environment. Wild! How do we know it changed sex? Because the clownfish that produce small gametes are male and the clownfish that produce large gametes are female.
Female hyenas have a “pseudo penis.” How do we know they are female? Because they produce large gametes, and the males produce small gametes.
Birds don’t have external sex organs, and don’t have XY or XX chromosomes (males have ZZ and females have ZW). So how do we know which sex are which? The males produce small gametes, and females produce large gametes.
Alligators don’t even have sex chromosomes—their sex is determined by environmental temperature as the fertilized eggs incubate. How can we tell which alligators are male and which are female? The males produce small gametes, and the females produce large gametes.
Chimpanzees are our closest living genetic cousins. How do we know what sex the chimps are? Males produce small gametes, and females produce large gametes.
Mammals (as well as most animals) are gonochoric, which means each member of the species is either male or female—and each organism’s sex cannot change at any point of it's life (despite what Jurassic Park claims, vertebrate animals do not all start off as female). If one would like to suggest that humans can change sex, that means that either mammals aren’t gonochoric, or that humans aren’t mammals. Mammals are gonochoric, which means that if humans can change sex, we will need to come up with a completely new evolutionary path in which humans specifically evolved on an evolutionary branch separate from all other mammals, don’t have common ancestors with other primates, and in which our sex is determined not by gamete size but by...? Proponents of this view would get along nicely with creationists who also deny evolution and claim humans are not related to other primates or mammals.
The third option is that humans are mammals—which are gonochoric, and any suggestion to the contrary is simply incorrect.
Some common misunderstandings:
“I thought you were male because you had XY chromosomes?” Chromosomes do not define sex. Instead, chromosomes determine sex in all mammals. Just as temperature determines sex in alligators. What defines sex is the size of gamete one has the potential of producing.
“My sociology professor said there are more than two sexes.” Sex refers to the size of gamete an individual organism produces. There are only two types of gametes, so in order for there to be any additional sexes, there needs to be additional gametes. Sperm, egg and...?
“I know a guy who said he feels like he is a woman and now identifies as female.” Identities are social, which is who you are (such as a golfer, photographer, friend, etc). Sex is biological, which is what you are (human, mammal, alive, etc). You can’t identify as having gills or not identify with having lungs. Likewise, you can’t identify out of your sex, as sex is not a mental state. I am male whether I like it or not—even when unconscious, even when brain dead.
“I don’t feel like a man though.” Being a man isn’t a feeling—it’s just a name for a sexually mature male human. You can have any personality trait, disposition, sexuality, etc, but that doesn’t make you more or less of a man. The ONLY thing it takes to make someone a man is to be an adult male, ie, having a body that can potentially produce small gametes.
“I got a vasectomy, so am I not a male?” You are still a male, just like a person who laser'd off all their hair is still a mammal. Your body developed around the potential production of small gametes—even if you suffered injury, a developmental/medical disorder, or had surgical intervention.
“You’re reducing people to their body parts.” No, I am defining male and female across the plant and animal kingdom based on the size of gametes they produce. As mentioned before, male is what your body is—it’s not your personality and doesn’t determine your value or worth.
“Saying someone can’t change sex is dehumanizing.” Humans are gonochoric, so claiming a person can change sex is literally to claim they aren’t human—which is dehumanizing by definition. Uno reverse! This claim is no different than saying it’s dehumanizing to state people can’t turn into frogs.
“What about people with Disorders of Sex Development, sometimes called intersex?” These are medical conditions that happen to males or females—not some blended category of sexed person. In order to have a blended category, you’d need to have a person that produces a blended gamete.
“This is just middle school science. We are way past this... sex is much more complicated.” Sexual development certainly is complicated. But the definition of male and female is quite simple: “In all plants and animals, the fundamental difference between the sexes is the size of their gametes.” -An Introduction to Behavioural Ecology, Page 180.
If someone wants to propose another definition of male and female, that’s fine, but it needs to account for the examples listed above and can’t be anthropocentric.
