What is Biological Sex ?

September 14, 2023

Perhaps you “know” what is “biological sex”, perhaps you still wonder after the deluge of strong affirmations that «sex is a spectrum» coming from the woke quarter. Here is something of use: the transcripts of an expert testimony in a case before of Texas appellate court.

Truly enlightening.

Before you start reading, some additional info:
– The expert: Colin Wright & Defendant’ witness
– Plaintiff: Lambda Legal Defense and Education Fund, inc. represented here by lawyer Omar Gonzalez-Pagan.
– Assistant Attorney general of Texas: Charles K. Eldred
– The context: a legislation piece (SB14) seeking to restrict sex-trait modification procedures (“gender-affirmative care”) to adults exclusively.

This report was produced by: Chavela Crain, CSR 3064 – 53rd District CourtTexas Certified Shorthand Reporter

IMPORTANT DISCLAMOR: this post is NOT intended to support Bill SB14 of Texas. We believe this bill invades without caution the field of medical expertise and will inadvertently withdraw medical support to young people who do certainly need all the help the medical profession can provide. However, we think this particular part of the hearings, the testimony of Dr Wright, clarifies a central tenet of biology: the exact nature of «biological sex» as opposed to «literature sex» and by doing so, disposes of the concept of «sex as a spectrum». Michel Virard.



ELDRED: What is biological sex?

WRIGHT: So at root, biological sex refers to the type of reproductive strategy that an individual has. So in what are called anisogamous species, these are species that reproduce by fusing two gametes of different sizes. The individual that produces the larger-sized gamete is called the female. The one who produces the smaller gamete or sperm is called the male. This is fundamentally what biological sex means. It refers to these reproductive strategies rooted in the type of gamete that they have the function to produce.

ELDRED: Would you say that biological sex is binary?

WRIGHT: Biological sex is binary because there are only two gamete types. There’s just sperm and there’s ova. So—so yes. So there’s only two options for an individual to have with respect to sex, and that is either male or female. There’s no third sex. There’s no third type of gamete, which would be the requirement for there to be a third sex or more.

ELDRED: Is there any sort of transitional gamete between a sperm and an egg?

WRIGHT: Not even close. They are widely different in sizes. And there’s never been a third intermediate gamete found in any species. And there’s reasons, evolutionarily speaking, why this is a stable strategy that has evolved independently many times across many different organisms.

ELDRED: And when you say species, are you including humans in that?

WRIGHT: Yeah, humans, any species that has two different sized gametes.

ELDRED: Insects as well?

WRIGHT: All—all animals and many plants.

ELDRED: Okay. How do you determine the biological sex of an individual?

WRIGHT: So this is an important point to make about some confusion on terminology. A lot of people, when they talk about how sex is determined, they conflate this with how sex is defined. As a biologist—so it’s a—in developmental biology, for instance, when we talk about how sex is determined, we’re talking about the mechanisms that cause an embryo to eventually develop into a male or a female, but that is very different from how sex is defined, which is based on the types of gamete that they can or would produce.

So there are many different organisms, different species that determine sex in a different way, such as alligators, for instance—they do it environmentally by temperature. But regardless of how sex is determined mechanistically and caused, the definition of sex across all of life, all plants, animals, is going to be rooted in those binary distinction between gametes.

ELDRED: Is it correct to say that in humans that biological sex is assigned?

WRIGHT: I don’t prefer that term because I think that suggests that it’s sort of an arbitrary designation, that it’s—

GONZALEZ-PAGAN: Objection, Your Honor. This is outside the scope of what biological sex is.

ELDRED: It’s not—

THE COURT: I’ll ask—well, hold on. Hold on. Let me just take a look. I’ll overrule the objection. I think you were completing your answer.

WRIGHT: Yes. I think that it suggests there’s ambiguity or that it’s an arbitrary designation. I tend to say that sex is observed and recorded. That’s—yeah, that’s what I should say.

ELDRED: So would you say biological sex is a spectrum?

WRIGHT: I would not say it’s a spectrum because that would require to have a spectrum of gamete sizes running all the way from the size of a sperm, which is very tiny, to the size of an ovum, which is very large. So no, sex is not a spectrum. It’s a—there’s two poles which correspond to either producing sperm or producing ova.

ELDRED: I want to show you a demonstrative. We’ll pull it up.

THE COURT: Yeah, if you’ve got a demonstrative, I’d prefer you show it to the other side first.

GONZALEZ-PAGAN: I’m unclear on the relevance of this exhibit, Your Honor, but—


ELDRED: We’re not offering it as an exhibit, just a demonstrative—testimony.


ELDRED: —just to help the


ELDRED: Oh, there it is.

ELDRED: What is that?

WRIGHT: So this is a figure that I created in response to this idea that sex is a spectrum and why that’s sort of a misleading way to talk about the biology of sex, because sex doesn’t come in degrees. You know, people aren’t just degrees of maleness and femaleness. For the vast majority of people, they are just either male or female, much like when you flip a coin, you’re either—you get heads or tails and it doesn’t come in degrees. There is a very small percentage of people who have intersex conditions whose genitalia appears sexually ambiguous.

ELDRED: I’m going to cut you off for just a second.


ELDRED: What do the numbers mean on the demonstrative exhibit up there you created?

WRIGHT: So those are just the percentage of the population that fall into these buckets of males and females and to be considered intersex, although the intersex category—much more of those individuals in that white box are also either male or female if you just investigate a little bit more about—regarding their gonads.

ELDRED: Well, explain a little bit more about intersex. What does it mean by intersex?

WRIGHT: So intersex refers to individuals whose genitalia appears ambiguous at birth or there’s a mismatch between your internal reproductive organs and your external phenotype.

ELDRED: Does the existence of intersex prove that there’s a spectrum of biological sex?

WRIGHT: No, it doesn’t, because intersex people, they don’t have reproductive organs that are organized around the production of a new third type of gamete that it would require for there to be another—a third sex. Anyone—to the degree that sexual ambiguity actually exists in humans—again, sexual ambiguity is not a third sex. There’s still only two sexes that a human can actually be.

ELDRED: How do chromosomes fit into this conversation?

WRIGHT: So in humans, mammals, and birds, and other organisms as well, chromosomes are a sex-determining mechanism if they have sex chromosomes. These are the causes of an individual’s sex. They have certain genes that reside on them that cause the embryo to develop down the pathway that results in a male or a female.

But as I mentioned earlier, how sex is determined, whether through chromosomes or environment, that doesn’t define an individual’s sex. So it wouldn’t be completely accurate to say that, you know, your chromosomes define your sex or that XX equals female or XY equals male. It really just comes down to the types of gametes that you have the function to produce.

ELDRED: Is it true there’s more than two different type of chromosomes—sex chromosomes for humans?

WRIGHT: So there’s, broadly speaking, two sex chromosomes, X and Y chromosomes, but those can vary in bodies differently. Some individuals can have different collections of chromosomes. They’re called sex chromosome aneuploidies. So, for instance, someone with Klinefelter syndrome has XXY chromosomes. This doesn’t mean that they’re a third sex because, again, chromosomes are just a cause of an individual’s sex. People with Klinefelter have a Y chromosome. And if they have an active gene on there called the SRY gene, that makes them 100 percent male. They develop into males. These differences in sex chromosomes, whether it’s XX, XY, XYY, et cetera—there’s several different combinations people can have—those represent variation within the two sexes. They’re not additional sexes beyond male and female.

ELDRED: I asked you about chromosomes. How about secondary sex characteristics such as facial hair in men, body shape of female, genitals and breasts and things like that? How does that fit into this conversation?

WRIGHT: Yeah. None of those define the sex of an individual. Those are downstream consequences of an individual’s sex. So if you’re biologically male and you have testes, you produce higher levels of testosterone. If you’re a female, you have ovaries. Those produce higher levels of estrogen. Each sex—both has testosterone and estrogen, just in different concentrations. But those hormonal mixtures that you get when they surge during puberty, they will create the sex-related secondary sex characteristics that we tend to see. Males, they grow taller. They get more facial hair, more body hair. Generally their voice deepens. Women—females, they grow breasts.

So these are traits that are, again, a downstream consequence of sex, but they do not define an individual’s sex in any way. You can’t modify, say, someone’s breasts and make them, you know, more male or female depending on the size that you make them. These are just related to sex, but they don’t define an individual’s sex.

ELDRED: And just to clarify, when you say if you modify someone’s breasts it doesn’t make them more or less female or male, you’re talking about biological sex female and biological sex male; is that right?

WRIGHT: Yes. Yeah. You can modify secondary sex characteristics. That doesn’t change what sex you are.

ELDRED: So when people say there are more than two biological sexes, do you agree?

WRIGHT: No, I don’t, because that would require a third type of gamete. Most people who make that claim are confused about the distinction between how sex is determined with chromosomes and how sex is defined, which leads people to say that there’s, like, six sexes because there’s six viable types of chromosome combinations people can have, but that’s not scientifically accurate.

ELDRED: Okay. Are there degrees of biological maleness or biological femaleness? Like, can someone be more biological male than someone else?

WRIGHT: No, because, again, sex is rooted in the type of gamete that your primary sex organs are organized around to produce. So in order for you to have a degree of maleness and femaleness that’s somewhere in between, you’d need to have—you know, to produce some sort of intermediate gamete that doesn’t exist.

ELDRED: Judge, I’d like to show another demonstrative.


ELDRED: What is this diagram on the screen?

WRIGHT: So this is a distribution of height among males and females in humans.

ELDRED: Did you make this diagram?

WRIGHT: I did not.

ELDRED: Okay. Do you know who did make the diagram?


THE COURT: Hold on.

GONZALEZ-PAGAN: —counsel just represented that he made the diagram.

THE COURT: Hold on. Let’s just get to the bottom of it. Who made the graph?

WRIGHT: This is—I pulled it off a paper, an academic paper. I’m not exactly sure which one. I’m sorry.

THE COURT: I don’t know that we need to use it, Mr. Eldred.

ELDRED: Okay. I apologize, Judge.

THE COURT: Okay. No worries.

ELDRED: Is it true that males and females—let me be more clear—that humans with biological sex male and humans with biological sex female have overlapping height distributions?

WRIGHT: They have overlapping distributions in height and many other different characteristics that are sex related or that sex influences but not sex itself.

ELDRED: And does that prove anything about whether biological sex is a spectrum?

WRIGHT: No, it doesn’t, because—you know, I’d like to reference that distribution. I think that’s important. Because a lot of people will say sex is a spectrum based on secondary sex characteristics, like breast size, for instance, how tall individuals are, the amount of facial hair. But really when you see the distribution, these are just sort of overlapping distributions and traits between males and females, but these traits don’t define an individual’s sex. So if you have a bimodal distribution like in that previous slide, as you go from one side to the other, you don’t—you just get higher or lower proportions of males and females that fall into those distributions, but that doesn’t mean that the sex is changing as you’re going from right to left or vice versa on a graph like that.

ELDRED: Did you read Dr. Shumer’s report submitted in this case?

WRIGHT: I did.

ELDRED: And I’m just going to read part of it to you. It’s in Paragraph 27. Sex is comprised of several components, including, among others, internal reproductive organs, external genitalia, chromosomes, hormones, gender identity, and secondary sex characteristics. Do you agree with that statement?

WRIGHT: I do not disagree—or sorry. I do disagree with that.

ELDRED: Why do you disagree?

WRIGHT: I think it just completely misconstrues what biological sex actually is because the sex of an individual, not just in humans but across, again, all animals and plants, is related to the type of gamete that you have the function to produce or would produce.

I would say that when he said internal sex characteristics, if he’s referring to gonads, then that would be accurate. But other things like chromosomes, again, these are upstream causes of sex. Secondary sex characteristics, they’re called secondary sex characteristics for a reason, because they are only downstream related effects of one’s sex. And the hormones are an example of the downstream consequence of one’s sex either. You know, those are sex-related traits, but they do not constitute what sex—the sex of an individual.

ELDRED: In Paragraph 32, Dr. Shumer said gender identity, like other components of sex, has a strong biological foundation. Do you have any opinion on that, whether that’s accurate?

WRIGHT: You know, I’m not an expert on gender identity, so I would actually like to not comment on that one.

ELDRED: Okay. Fair enough.

ELDRED: Bear with me just one second, Your Honor, please.

THE COURT: Uh-huh.

ELDRED: I’ll pass the witness, Your Honor.



GONZALEZ-PAGAN: Dr. Wright, you testified that reproduction—sex is defined based on reproductive capacity and production of gametes across all animal species; is that right?

WRIGHT: It’s defined by not whether you can actually produce gametes but if you have the function to, which would be rooted—related to the type of gonads that that would normally produce them.

GONZALEZ-PAGAN: Sure. And sorry. It takes—

WRIGHT: And it’s universal, yes.

GONZALEZ-PAGAN: Yes. And I need to go back a little bit. My biology training as a major takes a little while to kick in. There are animal species that reproduce without gametes; is that right?

WRIGHT: Absolutely. Yes, there are.

GONZALEZ-PAGAN: That includes aphids within your field of entomology?

WRIGHT: Yes. They reproduce by budding off of one another, parthenogenesis.

GONZALEZ-PAGAN: And to clarify, you’re not offering any opinions on the biological basis of gender identity?


GONZALEZ-PAGAN: You’re not offering any opinions on the biological basis of gender dysphoria?


GONZALEZ-PAGAN: You say that individuals who say that sex is defined by anything other than gametes or the capacity to produce gametes are mistaken; is that correct?


GONZALEZ-PAGAN: Okay. Would it surprise you to learn that some of the State’s designated experts have testified both in court and to the the Legislature that sex is defined by chromosomes?

WRIGHT: I’m not surprised, but that is an incorrect assessment. Sex is not defined by an individual’s chromosomes. It’s determined by them.

GONZALEZ-PAGAN: Would you agree then that your views shared today about sex are not universally accepted within the scientific community?

WRIGHT: I think there’s a lot of people who have misconceptions about sex in the scientific community, but I think if you get to the researchers who are studying the evolution of sex in a fundamental way, there’s—there’s no disagreement about what constitutes an individual’s sex.

GONZALEZ-PAGAN: But my question was were your views accepted within—universally accepted within the scientific community.

WRIGHT: I think a vast majority if polled would agree with me.

GONZALEZ-PAGAN: And what’s the basis for that statement?

WRIGHT: This has been a longstanding discovery of basic biology for a very long time, hundreds of years.

GONZALEZ-PAGAN: And you have not published in the area of sex determination or what it means to be a biological sex in scientific literature; is that right?

WRIGHT: I’ve written peer-reviewed book chapters on what sex is across all of—all of life, yes.

GONZALEZ-PAGAN: This is one book that was published this year that includes, among others, Michael Biggs and other authors, all of whom are opponents of gender-affirming medical care; is that correct?

WRIGHT: I was asked to write a chapter about the biological basis of sex, and so that’s what I—what I wrote about.

GONZALEZ-PAGAN: Can we pull up Plaintiffs’ Exhibit 48, please?

THE COURT: It’s not been admitted. Are you going to admit it through him?

GONZALEZ-PAGAN: Well, I’m going to show it as a demonstrative, Your Honor, just like the other ones.

THE COURT: Okay. As long as we make sure we’re clear about that and that it’s a demonstrative as opposed to—

GONZALEZ-PAGAN: Yes. Not a—pre-marked non-admitted exhibit, Plaintiffs’ Exhibit 48.

THE COURT: Got it. P-48, not an admitted exhibit.

GONZALEZ-PAGAN: Do you recognize this document?

ELDRED: How is this a Your Honor? I don’t understand.


THE COURT: Well, hold on.

WRIGHT: —not immediately, no.

GONZALEZ-PAGAN: Well, it’s an impeachment, Your Honor. He states that his views are universally shared. This is a peer-reviewed article that I’ll show shows otherwise.

THE COURT: Which might be appropriate to use, but if you’ve got a hard copy maybe so that he can see the whole thing, that would be the way to do it.

GONZALEZ-PAGAN: We’re happy to provide the witness with a hard copy, Your Honor.

THE COURT: I’m sorry?

GONZALEZ-PAGAN: We’re happy to provide the witness with a hard copy.


GONZALEZ-PAGAN: And it is in the Box.

THE COURT: Is there a hard copy?

DYER: It is in the Box?


DYER: Oh. Was it updated yesterday?

GONZALEZ-PAGAN: It was updated earlier today.

DYER: Oh, I didn’t know there was any additions to the Box.

STONE: Were there other updates today to the Box?

GONZALEZ-PAGAN: Your Honor, if I may, just to pause the time.

THE COURT: Yeah, let’s go off the record.

(Discussion off the record)

THE COURT: And Dr. Wright has a copy of P-48. Just give him an opportunity to kind of look through it before you ask him some questions.

GONZALEZ-PAGAN: Thank you, Your Honor.

WRIGHT: All right. I think I’ve read articles that are very similar in scope to this one before that make similar claims, so I think I can address your questions.

GONZALEZ-PAGAN: Thank you. Having reviewed Exhibit Plaintiffs’ 48, which hasn’t been admitted, have—would you dispute that some scientists believe that sex is multifaceted?

WRIGHT: I believe some scientists are mistaken about what biological sex is, yes.

GONZALEZ-PAGAN: Sex can have multiple meanings; is that correct?

WRIGHT: I mean, if we’re going to say sex can be an act with intercourse, that’s one other use of the word sex. But if we’re talking about the sex of an individual, what sex a person is, that has a very specific meaning in biology.

GONZALEZ-PAGAN: Is it your understanding that the sex on a birth certificate or a driver’s license has to always be consistent with—or a college application has to always be consistent with somebody’s genitalia and their production of gametes?

ELDRED: Objection. This is outside the scope of his expertise.

THE COURT: I’ll sustain that objection, if you have another question.


GONZALEZ-PAGAN: You earlier testified that sex—biological sex can be bimodal; is that correct?

WRIGHT: I do not think sex is bimodal. It is binary.

GONZALEZ-PAGAN: Would you agree that some sex characteristics are multimodal?

WRIGHT: Some sex-related characteristics can be bimodal and perhaps multimodal. I would need specific examples. But again, those are downstream consequences of sex. They don’t define an individual’s sex.

GONZALEZ-PAGAN: And again, aside from the letter to the editor and the chapter in the book that was published this year by individuals that harbor views against the provision of gender-affirming medical care, you have not published or researched in the area of what biological sex means?

WRIGHT: Outside of the publications I have on the topic, there are no additional ones.

GONZALEZ-PAGAN: You would agree that having a credential alone is insufficient to offer expert opinions on the subject; is that right?

WRIGHT: Absolutely.

GONZALEZ-PAGAN: Yet your opinions today are based solely on your understanding as an evolutionary biologist?

WRIGHT: It’s based on my understanding of the biology, again, the universal characteristics that unite all males and females across the plant and animal kingdom, not simply just looking at humans.

GONZALEZ-PAGAN: Let me ask you this. Do you believe that being transgender is a delusion?

THE COURT: Is a what?

ELDRED: Objection. This is outside—

THE COURT: I’m sorry. I didn’t understand.


THE COURT: A delusion. Okay. And your objection?

ELDRED: I’m sorry. What was the question again?

GONZALEZ-PAGAN: Do you believe that being transgender is a delusion?

ELDRED: I think that’s outside—I object that it’s outside the scope of what he’s been offered as his expertise.

GONZALEZ-PAGAN: It goes to bias, Your Honor.

THE COURT: I’ll overrule the question, if you can answer.

WRIGHT: What do you mean by transgender?

GONZALEZ-PAGAN: Do you believe that being transgender is a delusion?

WRIGHT: I would need to know how you’re defining the term whether I can make a claim on that. If you’re asking me whether I believe someone who is one sex who believes they are actually the other sex despite the type of gamete that they can or would produce, I would say that that specific belief would be a delusional belief if they’re actually identifying as the sex that they are empirically not.

GONZALEZ-PAGAN: Let’s show Exhibit—Plaintiffs’ Exhibit 51, which has not been admitted to the record.

THE COURT: So as a demonstrative. As a demonstrative, P-51.

GONZALEZ-PAGAN: Do you see it on your screen?

THE COURT: You should see it both places, but whichever works best.

POLLARD: Your Honor, may I approach to retrieve the laptop?


GONZALEZ-PAGAN: Do you recognize this?


GONZALEZ-PAGAN: It is a screen capture of an Instagram post by @swipewright on April 10, 2022; correct?

WRIGHT: That looks like what it is, yes.

GONZALEZ-PAGAN: And @swipewright is your Instagram account; is that right?

WRIGHT: It’s my Twitter and Instagram.

GONZALEZ-PAGAN: And on this post on April 10th, 2022, you stated in part: “The medical establishment has somehow convinced itself that it’s more conducive to a delusional person’s mental health to have all society participate in their delusion than to bring them in touch with reality.”

Is that what you wrote?

ELDRED: Objection, Judge. This is not a demonstrative exhibit. This is outside the scope of his expertise. His opinions outside the scope of his expertise should not be admissible. He’s not testifying as just some guy with opinions. He’s testifying as an expert on biological sex. And what he thinks about—this opinion on this tweet has nothing to do with his opinion on biological sex.

THE COURT: Well, you’ve put him up as an expert, and so I guess this potentially goes to bias, but I need you to offer the exhibit, sir, in order to move forward with it.

GONZALEZ-PAGAN: Is that what you wrote, Dr. Wright?

WRIGHT: That is what I wrote.

GONZALEZ-PAGAN: Your Honor, at this time I would move for the admission of Exhibit—Plaintiffs’ Exhibit 51.

THE COURT: All right. And then your objection?

ELDRED: Yes, Your Honor. Same objection. This is not relevant to the witness’ testimony. This is just something he wrote on Twitter, not within his expertise. He’s not here testifying about his opinions on things. It’s also hearsay.

THE COURT: All right. The objection is overruled and P-52 [sic] is admitted.

(Plaintiffs’ Exhibit 51 admitted, as clarified later by the Court on Page 255)

GONZALEZ-PAGAN: In this post, you’re referring to transgender people; correct?

WRIGHT: I’m referring to anyone who identifies with a biological sex that they are empirically not. So to the degree that a transgender person believes incorrectly that they are the opposite sex, that is the target of this tweet.

GONZALEZ-PAGAN: And by bringing them in touch with reality, you mean having transgender people live in accordance with their birth sex based on their genitalia?

WRIGHT: No. I would say that they just need to understand that their sex cannot literally be changed. So I’m okay with trans people choosing to medically transition if they would like to for adults, for instance, but I think it’s important that they understand that you can’t literally become the opposite sex merely by changing a host of secondary sex characteristics. So when I say in touch with reality, that’s what I mean, that they need to understand what their sex is and that they’re only making cosmetic changes.

GONZALEZ-PAGAN: Previously you stated that even asking a person what their pronouns are is a form of indoctrination.

ELDRED: Objection, Judge. This is not part of his expertise. In fact, he’s already testified he does not know anything about—he’s not testifying as an expert on gender identity.

THE COURT: I’ll sustain that objection, if you have another question.

GONZALEZ-PAGAN: Do you believe that being asked what pronouns somebody uses makes kids transgender?

ELDRED: Objection. Same objection, Judge. This is outside of his expertise. He’s not an expert on gender identity.

GONZALEZ-PAGAN: Your Honor, it goes to his bias. He’s never even published in this area.

THE COURT: Well, I think we’re—I don’t know that we need anything more on that. So for saving time, I’m going to sustain the objection.

GONZALEZ-PAGAN: Thank you, Your Honor.

THE COURT: Do you have any other questions?

GONZALEZ-PAGAN: In that case, no more questions, Your Honor.

THE COURT: Okay. Any redirect, Mr. Eldred?

ELDRED: Can I have one second to consult?


ELDRED: No questions, Judge.

THE COURT: All right. Thank you. Dr. Wright, you are done on the witness stand. You may be excused.

WRIGHT: Thank you.

Michel Virard