Sex is real: this doesn’t mean every living thing is either male or female

C C Offline

INTRO: It’s uncontroversial among biologists that many species have two, distinct biological sexes. They’re distinguished by the way that they package their DNA into ‘gametes’, the sex cells that merge to make a new organism. Males produce small gametes, and females produce large gametes. Male and female gametes are very different in structure, as well as in size. This is familiar from human sperm and eggs, and the same is true in worms, flies, fish, molluscs, trees, grasses and so forth.

Different species, though, manifest the two sexes in different ways. The nematode worm Caenorhabditis elegans, a common laboratory organism, has two forms – not male and female, but male and hermaphrodite. Hermaphroditic individuals are male as larvae, when they make and store sperm. Later they become female, losing the ability to make sperm but acquiring the ability to make eggs, which they can fertilise with the stored sperm.

This biological definition of sex has been swept up into debates over the status of transgender people in society. Some philosophers and gender theorists define a ‘woman’ as a biologically female human being. Others strongly disagree. I’m addressing those who reject the very idea that there are two biological sexes. Instead, they argue, there are many biological sexes, or a continuum of biological sexes.

There’s no need to reject how biologists define the sexes to defend the view that trans women are women. When we look across the diversity of life, sex takes stranger forms than anyone has dreamt of for humans. The biological definition of sex takes all this in its stride. It does so despite the fact that there are no more than two biological sexes in any species you’re likely to have heard of. To many people, that might seem to have ‘conservative’ implications, or to fly in the face of the diversity we see in actual human beings. I will make clear why it does not.

I call this the ‘biological’ definition of sex because it’s the one biologists use when studying sex – that is, the process by which organisms use their DNA to make offspring. Many philosophers and gender theorists will protest at making the creation of offspring foundational to how we define sex or distinguish different sexes. They’re surely right that sex as a social phenomenon is much richer than that. But the use of DNA to make offspring is a central topic in biology, and understanding and explaining the diversity of reproductive systems is an important scientific task. Gender theorists are understandably worried about how the biology of sex will be applied – or misapplied – to humans. What they might not appreciate is why biologists use this definition when classifying the mind-stretching forms of reproduction observed in limpets, worms, fish, lizards, voles and other organisms – and they might not understand the difficulties that arise if you try to use another definition.

Many people assume that if there are only two sexes, that means everyone must fall into one of them. But the biological definition of sex doesn’t imply that at all. As well as simultaneous hermaphrodites, which are both male and female, sequential hermaphrodites are first one sex and then the other. There are also individual organisms that are neither male nor female. The biological definition of sex is not based on an essential quality that every organism is born with, but on two distinct strategies that organisms use to propagate their genes. They are not born with the ability to use these strategies – they acquire that ability as they grow up, a process which produces endless variation between individuals. The biology of sex tries to classify and explain these many systems for combining DNA to make new organisms. That can be done without assigning every individual to a sex, and we will see that trying to do so quickly leads to asking questions that have no biological meaning.

While the biological definition of sex is needed to understand the diversity of life, that doesn’t mean it’s the best definition for ensuring fair competition in sport or adequate access to healthcare. We can’t expect sporting codes, medical systems and family law to adopt a definition simply because biologists find it useful. Conversely, most institutional definitions of sex break down immediately in biology, because other species contradict human assumptions about sex. The United States’ National Institutes of Health (NIH) uses a chromosomal definition of sex – XY for males and XX for females. Many reptiles, such as the terrifying saltwater crocodiles of northern Australia, don’t have any sex chromosomes, but a male saltie has no trouble telling if the crocodile that has entered his territory is a male. Even among mammals, at least five species are known that don’t have male sex chromosomes, but they develop into males just fine. Gender theorists have extensively criticised the chromosomal definition of human sexes. But however well or badly that definition works for humans, it’s an abject failure when you look at sex across the diversity of life.

The same is true of ‘phenotypic sex’, the familiar idea that sex is defined by the typical physical characteristics (phenotypes) of males and females. Obviously, this approach will produce completely different definitions of male and female for humans, for worms, for trees and so forth. Incubating eggs inside your body, for example, is a female characteristic in humans but a male one in seahorses. That doesn’t mean that human institutions can’t use the phenotypic definition. But it isn’t useful when studying the common patterns in the genetics, evolution and so forth of female humans, female seahorses and female worms.

Understanding the complex ways in which chromosomes and phenotypes relate to biological sex will make clear why the biological definition of sex shouldn’t be the battleground for philosophers and gender theorists who disagree about the definition of ‘woman’. There might be very good reasons not to define ‘woman’ in this way, but not because the definition itself is poor biology. Why did sexes evolve in the first place? (MORE)
Syne Offline
Conflating the diversity of biological sex in different species to justify diversity of gender expression in humans is intellectually dishonest. This is the worst kind of motivated reason. Biological sex objectively does define fair competition in sports, as evidence every sport that allows biological men to compete against biological women. And that's as far as we have to look to know that this whole article is unscientific crap.

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