The Biology of Sexual Identity, or Something Else?

The Kansas School Naturalist is a publication of Emporia State University. It publishes booklets on various topics. Its purpose is to provide information for people who are involved in science education. Each booklet covers a specific, often current, topic and provides a “proper” scientific understanding of the topic.

I put “proper” in quotation marks because there are some topics covered by this publication that are quite controversial, particularly when they lean into moral issues. Now, this is not the case for every publication of The Kansas School Naturalist. I have one in front of me on the classification of viruses.[1] I have not read it yet, but I expect that it will not cover any controversial topics: it is just about the nature and classification of viruses.

However, some issues of the The Kansas School Naturalist deliberately discuss controversial topics. For example, I have another issue in front of me. This one is titled: “XX-XY: The Biology of Sexual Identity and Gender Identity”.[2] 

Now, I picked up “The Biology of Sexual Identity” expressly because I knew it covered a controversial topic. As much as we conservative Christians claim that “your chromosomes determine your sex” or “the difference between girls and boys is obvious,” I knew that those who claim that transgenderism and homosexuality are okay, or even necessary at times, had “scientific” answers to these topics. I wanted to see what their arguments were.

Part of the booklet describes embryo sexual development. The authors talk about how the female body plan is the “default” body plan. That is, a human embryo always begins developing along the female body plan. However, if the right trigger is present, the embryo can be taken off of the female development plan and instead begin a separate track that leads to the individual being a male. That trigger is the testis-determining factor found on the Y chromosome. Put another way, if no Y chromosome is present, then an embryo will become a female by default. If a Y chromosome is present, that will trigger the male developmental pathway, resulting in the child being a male.

“See!” you may say. “Even they admit that XY leads to male and XX leads to female.”

Unfortunately, things are not that simple. See, there are several other triggers that are needed to get a female body or to get a male body. For example, the testis-determining factor is only the first step in creating the male pathway. All that does it turn the gonads into testes. That is it. To understand what happens next, we need to understand that early in embryo development, the sex organs are undifferentiated. There is a pair of gonads that can either become the ovaries or the testes. Associated with these undifferentiated gonads are two pairs of ducts: the Müllerian ducts and the Wolffian ducts. The Müllerian ducts can become the uterus and fallopian tubes and the Wolffian ducts can become the vans deferens, seminal vesicles, and ejaculatory duct. It is important to note that while the Müllerian ducts are the female structures, they are not yet a true uterus and fallopian tubes. Similarly, while the Wolffian ducts are male structures, they are not the vans deferens, seminal vesicles, and ejaculatory duct just yet. Both need to be triggered to begin that development. If the gonads become ovaries (because the testis-determining factor is absent), then the newly developed ovaries release hormones that cause the Müllerian ducts to begin developing into a uterus and fallopian tubes and causes the Wolffian ducts to degrade, since they are not needed. The reverse happens when the gonads become testes.

That is just a couple aspects of sexual development. However, it should be apparent that there is a chain reaction: the presence of a Y triggers the development of the testes which in turn triggers the development of the Wolffian ducts. There are several more parts to the chain, but this brief explanation is sufficient to note that parts of the chain can be disrupted. For example, chromosomes may not separate properly. The result can be an egg or a sperm that has an extra chromosome or is missing a chromosome. The result can be a person who has the combination XXY: two X chromosomes and a Y. Such a person develops into a male, since he has the Y chromosome with its testis-determining factor. However, he is usually sterile, because the pair of X chromosomes affects the development of the testes. He may also have a few feminine traits, again because of the influence of the pair of X chromosomes. In another example, a child may be female, but because of certain medication taken by the pregnant mother (such as synthetic progestinic hormone), parts of the external anatomy will resemble male anatomy (there will be a small flap that resembles a penis). In this case, the signaling pathway worked fine, but an additional signal (the medication) gave the wrong signal at the wrong time, causing the partial development of the wrong structure.

By the way: these sorts of things are not theoretical: there are cases where they have actually happened. Perhaps the most extreme case of this are individuals with complete androgen insensitivity. In this case, the individual’s body cannot recognize the presence of testosterone, so even though the individual has the XY chromosomes and produces testes, none of the proper development of the sex organs occur. The result is that the person’s entire body is designed like a female. Testes are present, but they are located where the ovaries would be, and the rest of the reproductive anatomy is female. Again, this is not theoretical: “The Biology of Sexual Identity” includes a picture of a baby who is genetically male yet physically female. Plus, I have read about cases like this outside of “The Biology of Sexual Identity,” so I know that the authors are not trying to hoodwink their readers. In short, it is not true that everyone born with XY chromosomes becomes male. As hard of a pill as it is to swallow, the mantra that a person with XY chromosomes is always a boy is not always true.

Now, there is an important point to be made here. It is clear that, as marvelous as is God’s design for the human body, things can mess up. The male and female developmental pathways that God designed work, but occasionally things go wrong. What happens when things go wrong? Sometimes, hormonal treatment or even surgery can correct what has gone wrong.

“The Biology of Sexual Identity” continues with its analysis. They cite a study which showed that the brains of transgender individuals were more similar to their chosen gender than they were to the gender they were born as. In other words, they claimed that a person born as a boy but transitioned to a woman had a brain structure that was more similar to the brain of a typical woman than it was to the brain of a typical man. Granted, they were looking at one particular part of the brain, namely the central subdivision of the bed nucleus of the stria terminalis. They did not claim that the entire brain of a transsexual individual was like a normal brain of their chosen gender, only that this one particular part of the brain was like their chosen gender.

Now we can see the reasoning of the authors. If we acknowledge that there are errors in the pathway to becoming a male or a female, such as a male who has XXY chromosomes or a female who has XY chromosomes, then a change in the brain may also indicate that the body has not developed the same way the brain has. Therefore, a transition or a sexual reassignment would be necessary to “correct” the “error” in development.

The authors of “The Biology of Sexual Identity” also address homosexuality. They cite studies that indicated that there are genetic and brain differences between heterosexual and homosexual individuals. It is worth noting that they were not adamant that these differences directly caused homosexuality, but only that they indicate a predisposition to homosexuality.

Now, at this point, it is easy for us conservative Christians to have a knee-jerk reaction. “No! There is no genetic predisposition to homosexuality! Genes and brain structure do not determine whether a person will become transsexual! I have heard different numbers! Your data is wrong!”

I want to step back from that knee-jerk reaction. First of all, it isn’t really productive. To adequately debate these points about genetics and brain structure of transsexuals and homosexuals, one would really need to research the topic. As in, become an expert in human sexual development and conduct your own research. Like it or not, unless we can produce those credentials, people like the authors of “The Biology of Sexual Identity” will dismiss us as “not knowing what we are talking about.” Even if we were to produce an expert who agrees with our statements, the debate will boil down to a “my expert is better!” argument, which will also fail to resolve the debate, because each party will think that his expert is the best one in the debate.

The second reason I want to step back from the knee-jerk reactions is because, as is evident from XXY males and XY females, the debate of sexual identity is not easy. We would like it to be as objective as possible, but it simply cannot be. If we insist that everyone who is born with XY is a male, do we expect every person with complete androgen insensitivity, who is genetically male but physically female, and has lived her whole life being a female, to “correct” her “problem” and become male? Don’t get me wrong: a person with complete androgen insensitivity does need some medical correction. These individuals typically fail to experience menstruation and need hormonal supplements to menstruate as a normal woman would. Do we say, “Since you already need medical intervention to be normal, I will insist that you just get a complete sexual reassignment so that your body matches your genes”? Again, these are people who have lived as females their whole lives. Are we in a position to tell them what they are “supposed to be”?

The fact that XY females exist is evidence of our fallen world. We live in a world where God clearly created two separate sexes, but ever since Adam’s sin, decay and destruction are now a part of the natural world. Therefore, errors in God’s perfect creation have occurred, and we get XY females.

It must be pointed out: my reasoning that XY females are a testament to our fallen world is a result of my acceptance of the Bible as the Word of God. I did not prove, using the best statistics and observations from science, that males are supposed to be XY and that females are supposed to be XX. I did not approach the problem logically, use analogy, or any other type of reasoning. I simply took it for granted that God created a very good world and that the world is now corrupted. On the face of it, such an approach may seem inadequate. After all, we want to convince people that transgenderism and homosexuality are unnatural, and how can we do that if people don’t believe that God created the world? There is the temptation to use something objective, such as science, logic, reason, and so forth, to “prove” that transgenderism and homosexuality are unnatural. However, we must remember that it is easy to confuse the issue of homosexuality and transgenderism. If different sexual identities can be put on a spectrum, ranging from XXY males to XY females to a female brain in the body of a male, where do we draw the line? Do we correct the feminine XXY male but leave the female brain in a male body alone? Why draw the line there?

If we try answering these questions using science or statistics, we end up with the “my expert is better than your expert” problem. Both sides of the debate insist that their studies and their experts actually define the issue, not the other guys, and no resolution is reached. If we try logic or reason, we need to define the foundations of our thinking. What concepts are considered to be true, how to we identify an idea as true, and so forth. But if our opponent does not agree with our assessment of what is true, then the problem still goes without a resolution. Instead, what we need is an outside authority, something that defines truth irrespective of human understanding, and use that authority to cut through the confusion of the sexual identity spectrum. That outside authority is the Bible. Let us explore the sexual identity spectrum and see how we can sort it out using God’s Word as a standard.

Let us begin with the easy topic to address: homosexuality. I call this one easy because, while it may be controversial, the Bible unambiguously addresses it. First of all, it is apparent from God’s Word that homosexuality is a sin. Paul is quite clearly speaking of homosexuality when he says in Romans 1:26-27 that

For this reason, God gave them up to dishonorable passions. For their women exchanged natural relations for those that are contrary to nature; and the men likewise gave up natural relations with women and were consumed with passion for one another, men committing shameless acts with men and receiving in themselves the due penalty for their error.

Lest someone try to dismiss this as simply “general sexual perversion,” note it specifically says that the men gave up their “natural relations with women and were consumed with passion for one another.” Yes, the more general term “shameless acts” is used later in the verse, but the description of men being passionate with other men describes nothing other than homosexuality. Moreover, if we understand that God had previously said in Leviticus 18:22 that “You shall not lie with a male as with a woman, it is an abomination” and in Leviticus 20:13 that “If a man lies with a male as with a woman, both of them have committed an abomination,” then it is clear that homosexuality is a perversion of Gods plan and should not be practiced.

What are we then to make of the idea that there are genetic predispositions to homosexuality or that the brains of homosexuals are structured differently from heterosexuals? A homosexual might argue, “If God made me this way, because He gave me my genes and my brain, why would He judge me for what I do by nature?”

I want to acknowledge that, once again, it is easy to answer this question by saying, “God did not make you that way because there is no genetic basis for homosexuality nor any difference in brain structure between homosexual and heterosexuals.” Again, the problem with this rebuttal is that it becomes a “my expert is better than your expert” argument. I do not claim to know enough details to refute the idea that there are genetic or brain correlations to homosexuality, nor do I know that my preferred experts are more correct than other experts.

But, for the sake of argument, and only for the sake of argument, let suppose that there is a correlation between genes and brain structure and homosexuality. Would that be sufficient reason to claim that homosexual practices are justified? Certainly not. For one thing, we have the very strong declarations in the Bible that homosexuality is an abomination. The way we perceive nature does not trump the Bible: that would put finite human suppositions above the word of the Creator of humans. By definition, the Creator will have superior knowledge and priority to the creature, so let’s go with what God says.

For another, even the authors of “The Biology of Sexual Identity” note that there might be a correlation between genes and homosexuality, but genes in and of themselves may not cause homosexuality. They say, “[w]hile there is no single gene, there is a slight influence from a combination of genes (polygenic) but this is not predictive.”[3] If the genes are not predictive of homosexuality, then genes are not the sole cause of homosexuality.

I was curious whether there were any other behaviors that also have a genetic component. So, I did a quick search. It only took me a couple of minutes to find scholarly articles that discussed and promoted a link between genes and violent behavior.[4] That is, these papers suggest that there is a genetic predisposition to violent behavior. Should we excuse violent behavior as simply a part of a person’s nature? I don’t think anyone would say that. For one, we punish violent behavior: we call them assault and battery and murder. The fact that these behaviors are punished shows that, regardless of where the behavior comes from, we hold the person responsible for his or her behavior. In fact, one of the papers just mentioned specifically noted that their model does not mean that people are hopeless. Rather, such behaviors can be controlled.[5] As Christians, we would certainly agree, since violence and murder are also prohibited by God, therefore they are acts people are expected to not do.

Using similar reasoning, can we not say that, regardless of whether there are genetic predispositions to homosexuality, people should still be expected to control those promptings? If homosexuality is clearly prohibited by scripture, then we should expect people to be responsible for homosexual acts, to be able to control those urges, regardless of where they come from.

“Oh,” a person may claim, “That is unhealthy. It is unhealthy to suppress who you are.” First of all, back to the genetic predisposition to anger, do we expect those with a predisposition to violence to act on those predispositions? No, we expect them to control it. Therefore, we should expect people who have a “predisposition to homosexuality” to also control that behavior. Arguing that it is “unhealthy to suppress who you are” presupposes that homosexuality is an inborn state of a person, that a person is homosexual by nature. If we understand homosexuality as an act (“man lying with man”) rather than a state of being, then this argument fades away.

What about transsexuals? Should a person who is physically male but “feels” female be allowed to have “corrective surgery” to make his body look the way he feels? In much the same way as I argued above about homosexuality, I do not believe so. Just because scientists can find similarities in the brains of a man who transitioned to be a woman and a person who is naturally a woman does not mean that there is an excuse for transsexuality. God gave us instructions about how men and women are to behave. That should be our guide in determining whether or not transsexuality is permissible.

Consider the purpose God had in making men and women. Read what it says in Genesis 1:27-28:

So God created man in his own image, in the image of God he created him; male and female he created them. And God blessed them. and God said to them, “Be fruitful and multiply and fill the earth and subdue it, and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth.”

Note that right after we are told about the creation of men and women as distinct human sexes, we are told why they were made as distinct sexes: they are to reproduce (“fill the earth”). In short, I believe that if you are born with the capability of doing the male side of reproduction, then you are a male. If you are born with the capability of doing the female side of reproduction, then you are female. No amount of physiological differences in the brain can change the fact that a person who has male anatomy is designed for doing the male part of reproduction and a person who has female anatomy is designed for doing the female part of reproduction.

Now, I want to address a couple of objections to the point I just made. Some may say, “Are you saying that people who are sterile are not male or female?” No, I am not, and you really shouldn’t take what I said that way. Nowhere in the previous paragraph did I say or imply that successful reproduction is needed to determine whether a person is a male or a female. If a person has a penis, scrotum, and all of the necessary structures to perform the male side of reproduction, he is male, even if he is impotent. I fully acknowledge that we live in a fallen world, and part of that fallen world is that things do not work as they should. Sometimes, a man or woman is incapable of reproducing, and that is simply because part of their body is not functioning properly. I in no way consider them to be less of a man or less of a woman because of problems within their bodies.

As a note, the idea of a males and females being defined by what part of reproduction he or she is able to perform extends to women who are genetically XY. As established before, people like this exist. I was rather surprised to learn that there are cases where women who have XY chromosomes have been capable of being pregnant and carrying a child to term.[6] Granted, these women were sterile: their gonads were undeveloped. They were not able to conceive on their own, so their pregnancies were made possible by using donated eggs. Also, the uteruses of these women were initially under developed, but that was helped with hormone treatments. Nevertheless, the fact that their bodies were so thorough designed for childbearing that doctors were able to help them begin and maintain pregnancies, I think, is a testament to the fact that these are women despite what their chromosomes may be.

Which leads me to address the second objection: “What about all of those poor people who have ambiguous sexual identification?” For one, I don’t think sexual identification is quite as ambiguous as some people may like us to think. Yes, there is an array of problems that can arise during the development of the sex organs, creating all manner of unusual developments of the sex organs. However, these people still can be recognized as belonging to one sex or the other. If these people need hormone treatment or corrective surgery to make their bodies more like the sex that they are, that is their choice to do so. Sometimes, it is necessary to prevent health problems. But that is a far cry from someone who is anatomically male deciding to have surgery to become female. That is no longer correcting an error in a fallen world, that is maligning one’s body.

That is my take away from all of this. People like the authors of “The Biology of Sexual Identity” confuse the matter. They treat all sexual diversion as a spectrum, with things like XXY males on the one hand with a fully male individual with some minor brain similarities to a female on the other. They are willing to lump all of this under the penumbra of “gender identity” and then claim that a person should choose a gender based on what is best for that person, even if what is best is based on a “feeling.” Because these people do not believe that God created humans as male and female, they see far too much plasticity between the two sexes. A proper view of the world, a view established the the One who created the world, instead allows us to understand the separate and distinct roles God gave to males and females and understand any deviations from a normal male or female pattern as either a result errors in human biological nature (for example, XXY males or XY females) or as a perversion of human behavior (for example, homosexuality or transgenderism).

Thoughts from Steven

[1]Faurquet, Claude and John Schrock (2006) “Classification of Viruses” The Kansas School Naturalist 53(1):1-15 

[2]Schrock, John; Dick Swaab; and Liana Zhou (2019) “XX-XY: The Biology of Sexual Identity and Gender Identity” The Kansas School Naturalist 63(2): 1-13

[3]Ibid. pg. 10

[4]Ferguson, Christopher and Kevin Beaver (2009) “Natural born killers: The genetic origins of extreme violence” Aggression and Violent Behavior 14: 286-294 and Meyer-Lindenberg, Andreas; Joshua Buckholtz; Bhaskar Kolachana; Ahmad Hariri; Lukas Pezawas; Giuseppe Blasi; Ashley Wabnitz; Robyn Honea; Beth Verchinski; Joseph Callicott; Michael Egan; Venkata Mattay; and Daniel Weinberger (2006) “Neural mechanisms of genetic risk for impulsivity and violence in humans” PNAS 103(16): 6269-6274

[5]Ferguson, Christopher and Kevin Beaver (2009) “Natural born killers: The genetic origins of extreme violence” Aggression and Violent Behavior 14: 286-294

[6]Kan, A. K. S., H. I. Abdalla, and T. Oskarsson (1997) “Two successful pregnancies in a 46,XY patient” Human Reproduction12(7): 1434-1435 and Plante, Beth and Marc Fritz (2008) “A case report of successful pregnancy in a patient with pure 46,XY gonadal dysgenesis” Fertility and Sterility 90(5): 2015.e1-2015.e1

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