Three Reasons Why There are Two–and Only Two–Biological Sexes.

Zach Elliot is an author of two books on sex and gender and a producer of 20+ animated videos on sex differences. Here is the intro to his article: “What Are Sexes? There is much confusion in our current culture as to what sexes are and what they are not.”

There is much confusion in our current culture as to what sexes are and what they are not. When biologists make a claim about the number of sexes in a species, they are not making a claim about chromosomes, body types, or personal identity; rather, they are making a claim about the number of distinct reproductive strategies in that species.

A reproductive strategy is an evolved system for propagating genes and forming a new individual. In sexually reproducing species, producing a new individual requires the combination of at least two distinct and complementary reproductive strategies. These strategies are fulfilled through the delivery of genetic material in sex cells called gametes, which have half the genetic material of the parent. When two gametes fuse, they form a genetically unique individual with a full set of chromosomes.

Some species reproduce through gametes of the same size (isogamy) and can have many unique reproductive strategies called mating types, which control what gametes can fuse with one another, but their differences do not go far beyond the molecular level. On the other hand, most species in the plant and animal kingdoms reproduce through gametes of differing size and form (anisogamy), where there is an asymmetry in size and behavior between the interacting gametes and often the individual organisms themselves.

When gamete sizes are differentiated (anisogamy), there are typically exactly two sexes, no more and no less. In such systems, the reproductive strategy that produces the smaller gametes is designated as male and the reproductive strategy that produces the larger gametes is designated as female. It is not the physical size of the gametes themselves that differentiates the male and female reproductive strategies, but rather what those size differences represent.

[Added December 2, 2022]

Zach Elliot discusses crocodiles and the fact that that there are only two sexes:

I had a discussion yesterday with an 18 year old male trans activist who thought atypical karyotypes like XXY were additional sexes.
By asking one simple question, I was able to change his mind.
Here’s how.

“How do we know the sex of crocodiles?” I asked. “They don’t have sex chromosomes at all.”
With this question, I accomplished two things: 1) challenged his assumptions and 2) piqued his curiosity through an interesting example.
His response said it all

Screen Shot 2022 12 02 at 2.45.21 PM

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Erich Vieth

Erich Vieth is an attorney focusing on civil rights (including First Amendment), consumer law litigation and appellate practice. At this website often writes about censorship, corporate news media corruption and cognitive science. He is also a working musician, artist and a writer, having founded Dangerous Intersection in 2006. Erich lives in St. Louis, Missouri with his two daughters.

This Post Has 5 Comments

  1. Avatar of Erich Vieth
    Erich Vieth

    Heather Heying writes:

    I am a biologist. While I abhor credentialism, I will say that the particular kind of biology that I do—evolutionary biology and animal behavior with a focus on sexual selection and the evolution of mating and social systems—allows me to say with confidence that there is no such thing as a non-binary they. That is a made-up category.

    In I Am a Woman: and a biologist (March 29), I take the obvious and yet somehow contentious position that women—which is not a made-up category—are adult human females.

    Adults are individuals who have attained the average age of first reproduction for their species. They have reached the age of maturity. The term adult applies across many species, and is used to distinguish them from juveniles, who are not yet capable of reproduction.

    Humans are members of the genus Homo. Our relatives in the genus Australopithecus, now extinct, are sometimes categorized as human as well. Every individual Homo sapiens is a human.

    Females are individuals who do or did or will or would, but for developmental or genetic anomalies, produce eggs. Eggs are large, sessile gametes. Gametes are sex cells. In plants and animals, and most other sexually reproducing organisms, there are two sexes: female and male. Like “adult,” the term female applies across many species. Female is used to distinguish such people from males, who produce small, mobile gametes (e.g. sperm, pollen).

    A bit later in the year, I ask What Do Girls Do? (October 4). My answer: Girls become women.

    There is an eight-year-old girl who likes to play in streams and look under rocks for squirmy critters. She not only knows how to throw a ball but enjoys doing it. She loves math and logic, and has no interest in dolls or dresses. She will grow up to be a woman. Because that’s what girls do.

    There is another eight-year-old girl who likes to give tea parties for her stuffed animals. She likes to dance all the dances, often with other girls who like to do the same thing. She loves to read, and has no interest in trucks or trails. She will also grow up to be a woman. Because, again, that’s what girls do.

    And yet, we are increasingly being told that we cannot believe our own eyes, our intuition, any of the science unless it’s ideologically captured pseudo-science, or even the 500 million to 2 billion year history, in our very own lineage, of having two and only two sexes. We’ve got something better than any of that. We’ve got pixie dust in the form of gender essence, and boy howdy is it all the rage. When little Johnny comes home from school asserting that he is a truck, you do not have to rush him to the body shop for emergency surgery and an oil change. But when he comes home asserting that he’s a girl, you’d best affirm his delusions, else you’re a very bad parent.

  2. Avatar of Sherry
    Sherry

    I appreciate your logical and well thought out examples and explanations. I am not a biologist. I am a mom of 2 boys and a girl sandwiched between. A week or so before my daughter had her third birthday, Lisa said, “When I have my birthday, I’m going to be a big boy like Robby.” Thinking she meant she would be older like her brother, I ignored it. But when she said the same thing a couple of times as birthday approached, I thought I should reassure her so I said, “When you were born and the doctor said, ‘We have a girl’ Daddy and I were SO happy! Now we had a boy and a girl, so when you have your birthday you’re not going to be a boy, you’re going to be our big gir….” That’s as far as I got. Lisa burst into loud sobs and covered her face! Days later she had a wonderful birthday and it never came up again.
    I wonder what would have happened to that little girl if I’d suddenly begun calling her Luke or Limon and referring to her in male pronouns because somebody told me she was a boy in a girl’s body. Of course we wouldn’t have done that but there is so much nonsense surrounding “gender” today that I worry about these kids whose parents go along with momentary thoughts that come from childrens’ mouths. When a child expresses the desire to be the opposite sex, there’s a reason. It needs to be addressed and assurances given. In Lisa’s case, she loved and admired her big brother and now there was a new baby brother in the house. It wasn’t rocket science.

  3. Avatar of Erich Vieth
    Erich Vieth

    Octavia Sheepshanks writes this at “How I learned to stop worrying and criticise the magazine.”

    I blame New Scientist for my unwavering conviction that humans have two sexes and that this matters. Humans are a gonochoristic species: each individual produces gametes of only one of two distinct sexes — male and female. We are also sexually dimorphic, with males and females tending to exhibit numerous differences in secondary sex characteristics. As a subscriber to New Scientist, I have had access to a reliable and rational source of information on these differences and why they matter. For example, in April 2022, New Scientist published the following:

    It’s one small step for a mannequin, one giant leap for womankind. Mannequins designed to represent female bodies will be sent into space for the first time on NASA’s Artemis I mission later this year to study how radiation affects women in space. [ … ] Organs such as breasts and ovaries are particularly sensitive to radiation, putting women at a greater risk of cancer caused by radiation than men.

    I believed it was self-evident that sexual dimorphism lies at the heart of female oppression, and that it is the foundation for feminism — yet it is now controversial to claim that the oppression of women is sex-based. It contradicts the idea that women are not oppressed because they are female (many now consider it neither necessary nor sufficient to be female to be a woman) but on the basis of an internal gender identity. I have never understood how such oppression could work but felt that saying so would cause pain. So I remained silent and continued to read New Scientist, sure that the truth would clarify the conversation and heal the hurt.

    Unfortunately, “the truth” has done no such thing, and New Scientist is no longer the safe haven it once was. I did not realise how much of my sanity relied on its recognition of the existence and importance of two sexes in humans until articles began to appear which seemed to deny this entirely. . . .

    I looked back at all the New Scientist articles that had confused me and found the original publications. They had been altered, too: every time only women or men (i.e., males or females) were being referenced, they said so, in stark contrast to New Scientist’s interpretation.

    Essentially, New Scientist is blithely misreporting published research to remove any implication of two sexes in humans. Presumably the purpose of these scientifically inaccurate linguistic gymnastics is to include those with alternative gender identities without causing offence.

    The alteration of scientific studies to avoid naming the demographic previously known as “women” has serious consequences for anyone female.

  4. Avatar of Erich Vieth
    Erich Vieth

    More from Heather Heying, this time from her article, “A meander through dominance, gender norms, and mastery.”

    [W]hat makes you male or female is your gametes—your sex cells. I see the sophists and their grade-school-level philosophy coming already, but here it is, again:

    Females are individuals who do or did or will or would, but for rare developmental or genetic anomalies, produce eggs. Eggs are large, sessile gametes.

    Males are individuals who do or did or will or would, but for rare developmental or genetic anomalies, produce small, mobile gametes. In animals, that’s sperm; in plants, it’s pollen.

    Very occasionally, people feel so at odds with the sex that they are that it is important to them to present to the world as the opposite sex. Most of what is passing for “trans” now, however, is not that. It is a confusion, a muddle, a betrayal of reality and of reason and of humanity and of the very individuals who are being encouraged in their beliefs. It is the opposite of empowering.

    I was a girl who liked to play ball and build things and do math, and I grew up to be a woman, because that’s what girls do. I insist on the reality of the binary nature of sex, and the inability of humans, as mammals, to change our sex. And I reject high-tech solutions like puberty blockers as solutions to “problems” that, for most people, are not persistent problems at all, but explorations in a journey of discovering who they are. Discovering yourself as you go through adolescence, seeking new ways to be, rejecting who you have thought yourself to be in the past, this is all normal and human. People both ancient and modern have gone through this—our long and winding childhoods are much of what make us human². What we are doing now is entrenching a confusion: “ah, I believe this right now, and I am certain that I will believe this forever, and so I will employ technological fixes in order to fix this moment, this belief, in place, as the forever mode.”

    It won’t work, though. It almost never works.

  5. Avatar of Erich Vieth
    Erich Vieth

    Colin Wright, author of “Understanding the Sex Binary: Accurate, nonpoliticized descriptions of biology are essential to crafting policy to preserve the integrity of female-only spaces.”

    When biologists claim that “sex is binary,” they mean something straightforward: there are only two sexes. This statement is true because an individual’s sex is defined by the type of gamete (sperm or ova) their primary reproductive organs (i.e., gonads) are organized, through development, to produce. Males have primary reproductive organs organized around the production of sperm; females, ova. Because there is no third gamete type, there are only two sexes that a person can be. Sex is therefore binary.

    It is important to note here that the binary nature of sex is compatible with sex ambiguity because ambiguity with respect to sex is not itself a third sex. However, many gender activists falsely assert that the “sex binary” must mean something like “every human who has ever existed and will ever exist can be unambiguously categorized as either male or female.” Given this, they contend that providing examples of people with ambiguous sexual anatomy (i.e., “intersex” conditions) not only disproves the sex binary but also demonstrates that biological sex is a meaningless and even oppressive categorization scheme. (We will leave aside for now the fact that many of these same activists do recognize an alternative version of “biological sex” in the form of gender-identity bio-essentialism, or the theory that a person’s subjective self-conception of male or female is rooted in the brain itself.)

    The chain of reasoning goes something like this. Sex is not binary because intersex people exist. Their existence demonstrates that biological sex is a spectrum. Since sex is a spectrum, that means no line can be perfectly drawn separating males from females. If no single line can be drawn, then anywhere someone chooses to draw one is totally arbitrary and subjective. If it’s totally arbitrary and subjective, then that means the categories male and female are also arbitrary and subjective “social constructs” with no firm root in biological reality. If that’s the case, why are we categorizing people in law according to these arbitrary labels instead of letting people simply label themselves? To do otherwise is to oppress people based on a biological falsehood.

    This is just how the argument is made, and it is made with stunning success. Children in K-12 are regularly taught these days that sex and gender exist on a spectrum. Parts of the scientific establishment and the medical profession have also embraced this idea…

    In both chromosomal and temperature-dependent sex determination systems, though an individual’s sex is mechanistically determined in different ways, it is always defined the same way—by the type of gamete his or her primary reproductive organs is organized around producing. This should be obvious, as it would have been impossible ever to have discovered these different sex-determining mechanisms without first knowing what males and females are apart from sex chromosomes and incubation temperatures.

    These efforts by activists serve a single purpose—to portray sex as so incomprehensibly complex and multivariable that our traditional practice of classifying people as simply either male or female is grossly outdated and should be completely abandoned in favor of “gender identity.” This entails that males would not be barred from female sports, prisons, or any other space previously segregated according to our supposedly antiquated notions of “biological sex,” so long as they “identify” as female, whatever that means.

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