in: Health, Health & Fitness, Podcast

Podcast #761: How Testosterone Makes Men, Men

What creates the differences between the sexes? Many would point to culture, and my guest today would agree that culture certainly shapes us. But she’d also argue that at the core of the divergence of the sexes, and in particular, of how men think and behave, is one powerful hormone: testosterone.

Her name is Dr. Carole Hooven, and she’s a Harvard biologist and the author of T: The Story of Testosterone, the Hormone That Dominates and Divides Us. Today on the show, Carole explains the arguments that are made against testosterone’s influence on shaping men into men, and why she doesn’t think they hold water. She then unpacks the argument for how testosterone does function as the driving force in sex differences, and how it fundamentally shapes the bodies and minds of males. We delve into where T is made, how much of it men have compared to women, and what historical cases of castration tell us about the centrality of testosterone in male development. We then discuss how T shapes males, starting in the womb, and going into puberty and beyond, before turning to its influence in athletic performance. We end our conversation with Carole’s impassioned plea for celebrating what’s great about men.

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Brett McKay:  Brett McKay here, and welcome to another edition of The Art of Manliness Podcast. What creates the differences between the sexes? Now, many would point to culture, and my guest today would agree that culture certainly shapes us, but she’d also argue that at the core of the divergence of the sexes, and in particular of how men think and behave, is one powerful hormone: Testosterone. Her name is Dr. Carole Hooven, she’s a Harvard biologist and the author of, “T: The Story of Testosterone, the Hormone that Dominates and Divides Us”. Today on the show, Carole explains the arguments that are made against testosterone’s influence on shaping men into men and why she doesn’t think they hold water. She then impacts the argument for how testosterone does function as the driving force in sex differences, and how it fundamentally shapes the bodies and minds of males. We delve into where T is made, how much of it men have compared to women, and what historical cases of castration tell us about the centrality of testosterone in male development. We then discuss how T shapes males starting in the womb and going into puberty and beyond, before turning to its influence in athletic performance. We end our conversation with Carole’s and passionately for celebrating what’s great about men. After the show is over, check out our show notes at

Carole Hooven, welcome to the show.

Carole Hooven:  Thanks so much for having me, Brett.

Brett McKay:  So you got a book called “T: The Story of Testosterone, the Hormone that Dominates and Divides Us”. So, you have spent your career studying the physiological and psychological effects of testosterone on humans and other animals. How did that happen?

Carole Hooven: Okay. Wow, I don’t know where to start. I guess I could start… I’ll just start by saying, when I graduated from college, I had no idea what I wanted to do, I just sort of got a regular job, I did that for 10 years, and then I decided that I wanted to go work with Richard Wrangham, who I know you’ve had on the show before, and the reason I wanted to do that is because I had been taking classes, and reading books and just trying to… And traveling, and trying to figure out what I really wanted to do when I grew up. And I read this book by Richard Wrangham called, “Demonic Males”, and I had really been focusing in on understanding human behavior, and I’d gotten really interested in neurobiology, then I discovered genetics and evolution and got really interested in that. And then I read Richard’s book, which used research on non-human primates, primarily chimps, as a way to understand the evolutionary and genetic origins of human behavior, particularly aggression, and I thought that was fascinating, and I thought that was something that I might be able to actually do, especially ’cause Richard was at Harvard at the time. And so I applied, quit my job and applied to the Harvard Graduate Program, and got rejected because I had no relevant experience, and then I really bugged Richard and some other people in the department, and I was like, “Look, I already quit my job. [chuckle] This is what I wanna do.”

And eventually, because I was persistent and enthusiastic, not because I had any special expertise, I have to say, Richard gave me an opportunity to go out to Uganda and study chimps for a year. I ended up getting evacuated because there was a lot of really awful violence and political upheaval around Uganda, in that region of Africa at the time, so I only spent eight months out there. But long story short, it was spending eight months in the jungle with chimpanzees surrounded by a lot of actual human aggression and violence that got me really interested ultimately in testosterone, because the way… If you… Anyone who goes and spends time with chimps can see that the sex differences in the chimpanzees in so many ways mirror sex differences in humans, just in these very broad patterns of the status and hierarchy, obsession among the males, competing largely for food and the right to have sex with the females who are in estrus, who can get pregnant. So there’s a lot of aggression, there’s a lot of status obsession in the males. They’re also capable, like humans are, of being kind and nurturing, and warm, and family-oriented in a way.

And the females, on the other hand, I never saw, although it does happen, I never saw any instances of female physical aggression. I saw it every single day among the males. And so there was just this very pronounced sex difference where there’s a lot of nurturing and caregiving among the females, just much more peaceful overall on… All of this is on average. And they don’t have any human culture, so there was nobody who was gonna be able to convince me after that experience that these similar patterns of sex differences in humans are primarily due to human culture. They’re not. They’re molded by human culture, the way they’re expressed is heavily dependent on human culture, but the evolutionary and genetic origins are in us. We’re born that way. And so that’s why I got interested in testosterone ’cause there’s no more powerful way of explaining human sex differences, which are… Male behavior in particular is a really important aspect of our lives.

Brett McKay: Yeah, one of the goals of your book is to push back some of these popular arguments out there that testosterone really doesn’t influence differences between the sexes. There’s lots of them. Can you briefly summarize the arguments against T’s influences on sex differences? Like, if it’s not testosterone, what are they saying is causing the sex differences?

Carole Hooven: Right. I’ve been asked this before, and I admit, I do find it challenging because… But it’s a really good exercise, and I try to do this in the book, which is to entertain the best argument from the opposition. So most critics, except for the most extreme ones, will acknowledge that the physical differences basically from the neck down are due to testosterone. So it really… You have to be kind of a nut job to deny that male size and strength overall, although there are nut jobs who are getting a lot of press, unfortunately, but that’s just really would be incredibly far-fetched to try to deny the science that testosterone at least explains the secondary sex differences in humans, so that’s high muscle mass, fat distribution, body hair, those kinds of things.

So most critics will acknowledge that testosterone is responsible for those physical differences. More reasonable critics, and I think this can play a really useful role in the science of testosterone and sex differences, most other critics deny that testosterone has any important effects on the brain, and thus, behaviour, and that it is not ultimately the most powerful driving force in those sex differences that I just talked about. So the largest sex differences that exist, and this is not my view, this is, in fact, I’m not talking about the cause, I’m just talking about the observation, are in sexual psychology and behavior and physical aggression.

So those are huge, consistent with non-human animals. We see them across ages, not the sex part, but across cultures. They’re just incredibly pervasive. And so those sex differences exist, but the question is, does testosterone influence the brain and behavior in ways that promote increased physical aggression in males and increased desire for variety and number of sexual partners. So those are the biggest sex differences, and those are the ones I really focus on in the book because there’s so much clear evidence that testosterone in the early developmental period around pre-natally and directly post-natally, and then in puberty and beyond, that those differences in exposure to that hormone and how it acts, coordinates the body, the physical adaptations of size and strength with psychological adaptations that enable male animals, including humans to take advantage of their larger body size, and the fact that they have sperm and a penis, that they have to be motivated to wanna get that sperm into the female reproductive tract, and to do that, especially over human evolutionary history, there had to be physical competition with other males for status or for the resources they need to acquire high status, which enable…

And that could be territory, now a lot of that is money and professional status. But doing all of that increases the chances that males will be able to have a higher number of sex partners ultimately. And there’s different strategies that males can use and we can get into that. So it might not be an increased number of sex partners, but it might be using one’s body and having the psychology to wanna use one’s body, or even just one’s sort of competitiveness and desire to elevate one’s status that could result in the acquisition of a high quality mate, where if you mate with that single female for life, you could do very well reproductively. It doesn’t mean that you have to have 10 kids, but it means you have to acquire that mate and have sex with her. So the adaptation is not the male desire necessarily for children, it’s the desire to either partner with one or a few mates and be a good partner, or play the field and have many different partners, there’s many different strategies. But… Sorry, this is a long answer, but the idea is that testosterone coordinates the psychological adaptations with the physical adaptations.

And I should just get back to the critics ’cause I’ve gotten off the topic here. But the critics are, to me, bizarrely denying that they’ll accept that testosterone acts on the body, but then are denying that it acts on the brain because they want to assert, and they do assert, that because we live in a gendered society, the default assumption should be that the sex differences that we observe are due to social and cultural influences. But this just doesn’t make sense from a scientific and evolutionary point of view. The default assumption is that we are like all of these other animals where testosterone does these very same things in males. It’s not a coincidence that it does the same thing in humans, it’s just that our culture can exacerbate those differences. They can minimize… The culture can minimize or kind of enlarge those differences or just budge the expression around. So it’s always gene, culture, interactions.

Brett McKay: Why do you think the critics are so reluctant to embrace the fact that T influences not just the body but the mind? What is the apprehension?

Carole Hooven: Yeah, I think it’s based on fear, which should not be playing a role in science and our efforts to understand reality. So even if the fear was true, if the fear was based in reality, so suppose the fear is that, well, if men are dominant to women and have power, commit rape, cheat on their wives, if that’s because of something in their genes, if that’s because their genes code for high levels of testosterone and testosterone promotes these behaviors, the fear might be, “Well, then there’s nothing we can do about it. Then we’re stuck with bad male behavior, and it justifies bad male behavior because it’s natural.” That’s called the naturalistic fallacy, by the way, the idea that what is found in nature is good. Anyone can see in two seconds that there’s plenty of things that are natural, like malaria, that are terrible. So that’s just a bad argument.

And there’s also plenty of evidence that we are definitely… That’s biological… The idea of biological determinism, that if something is in our genes, it’s immutable and we’re stuck with it and we have to accept it. Of course, that’s not true either. And all you have to do is look around the world at different cultures and different societies and see what the differences in, say, the rates of murderers, because males commit across the world about 95% to 98% of all murders, but in some cultures, the sex difference in the murder rate and the murder rate itself is incredibly low. And I always use Singapore as an example because it’s extremely safe, people, especially women can walk around feeling safe because the sexual assault is incredibly low, physical aggression committed by males in general is extremely low, and that’s because of their culture and harsh penalties for those crimes. So…

And that’s just one example, and we know that there are examples on the other end. I was just talking to a grad student in my department who is from India, and he was… And I know the data on India. But sexual assault is rampant because it hasn’t been taken seriously in India by the government there, and you can get away with it. And so men, if you can get away with it, men are going to do it, and they do. So the idea is that genes and testosterone sort of lower the bar for the expression of those behaviors in the right environmental circumstances, but that doesn’t mean that the environment can’t shape heavily the expression of those behaviors. So males are definitely more inclined to those behaviors, but we know that there’s all kinds of things we can do to tamp down the expression of those behaviors, and that’s clear from just even looking across cultures, or even across time, and how we’ve changed over time. Our genes haven’t changed, but the laws have, and the social norms have.

Brett McKay: Okay, let’s dig into the basics of testosterone. I think everyone has a general idea of what it is, it’s a male… All male and females have testosterone, but males…

Carole Hooven: That’s right.

Brett McKay: Males have more testosterone. Where is it made in the body and what are the difference in testosterone levels in men and women?

Carole Hooven: So testosterone… First of all, in adulthood, males have anywhere… In puberty, males can have 10 to 30 times the level of testosterone as women, but in western well-fed populations, it’s about 10… Males have about 10 to 20 times as much as females, adults, that is. And there’s no overlap in testosterone levels in healthy normal populations of men and women. And so in men, about 95% of testosterone comes from the testes, and the rest of it comes from, mostly from the adrenal gland, and there’s some other sources. Testosterone is actually made by many tissues, it’s even made in the brain, so it can… Most of it comes from the testes, and then can enter the brain, but it can also be made de novo in neurons, which is really interesting. And I should just… And so in females, about half is made in… These very, very low levels are made in the ovaries, and then the rest is made in the adrenal glands and in fat cells. So also, and I should just say, estrogen comes from testosterone. So testosterone is converted into estrogen in males and females, and males also make estrogen, and males who have more body fat are gonna have more of the enzyme, which is called aromatase, that converts testosterone into estrogen.

So men who have a high level of adiposity can start to develop some feminine features like gynecomastia, AKA man boobs, and that’s because the estrogen levels can really rise due to this high activity of this aromatase enzyme. So in females, estrogen can come from conversion of testosterone in various tissues and from precursors to testosterone that are produced in the adrenal gland, that can then also be converted to testosterone in other tissues. And I should just say that testosterone is an androgen, and there are different androgens and our body’s testosterone is the main one, but there were other ones like dihydrotestosterone, which is also a product of testosterone conversion, and all the androgens interact with what’s the androgen receptor and… Like a key in a lock, basically. And the androgen receptor is present in many, many tissues, again, also in our nervous system and our brain. And what’s interesting is that the sex steroids, which are estrogen, progesterone, testosterone, DHT, can all, because they’re steroids, because they’re fatty molecules, they’re lipophilic, they can go into any tissue in any cell. They can just cross the blood-brain barrier, they can get right through cell membranes, inside cells and they affect gene transcription once they’re inside cells. So they’re very, very powerful and they can go everywhere and have these long-term systemic effects on us.

Brett McKay: I think it’s interesting to note that our knowledge of testosterone is relatively new. It wasn’t until the 1920s that scientists were able to actually pin down testosterone, the hormone.

Carole Hooven: Right.

Brett McKay: But before that, they… Scientists, people, humanity had a hunch that the testicles were involved in masculinizing men. And there’s some interesting, I guess we can call them natural experiments that happened throughout human history where we were able to figure out there’s something going on with the testicles that cause men to be men, and one of them is this really interesting thing in Italy, church choirs would castrate young boys basically, and they called it Castrati. Can you tell us about that? What do we learn about testosterone from that?

Carole Hooven: Yeah, so this is disturbing. I do talk a lot about castration in the book, over the ages and in different cultures, and I learned a tremendous amount and it was all gross [chuckle] because I did get… It’s not funny, I did get into the procedure, and there’s also Unix in Imperial China, and the way that they were castrated was particularly horrific, but most of the history of castration. So if we just start with the Castrati in, say, 18th century Italy, these are… What happened was, there was a lot of poverty and there were opportunities for kids who were pre-pubertal who were singers, to gain fame and fortune by singing in church choirs, some of them could gain great fame and fortune, but even if they didn’t have great fame and fortune, they could have some fortune at least, and help out their families. And so every year, thousands of young boys were castrated in the hopes of sort of making it big and making it to a church choir, and this is before there was any anesthetic. So a lot of them died, and most of them did not make it and had to live lives of a eunuch.

So what happens is, if a kid, a boy is castrated prior to puberty. So most of the people listening are men who have gone through puberty, and you know exactly what happens when you go through puberty, to your body, to your psychology, to your voice, and sometimes to your hair. Some people start going bald fairly soon after puberty, but a eunuch never goes bald. And so what happens is, if you remove the testes prior to puberty, and again, yes, this is before anything was known about testosterone, but there were these predictable changes where the period of childhood growth continues for a long time, and the reason is that in puberty, it is actually rising testosterone that is converted primarily into estrogen even in boys, that causes the growth of the long bones, and that when it plateaus towards the end of puberty, that causes the growth plates in the long bones to seal, and that is why growth, the height spot stops at the end of puberty, it’s actually because of estrogen coming from testosterone even in boys.

But the point is, if you remove the testes, you never have that testosterone increase during puberty and that growth hormone generated childhood growth, like I have a 12-year-old boy, he’s still in that sort of growth hormone period, he’s transitioning now to… Testosterone is gonna be taking over and… But that period is extended, so you get this longer period of childhood growth, and the castrated men can end up to be very tall because they don’t have that testosterone peak where growth ends. So they can be very tall and they don’t get those secondary sex characteristics that most of your listeners will have developed during puberty. So they retain their head hair, their voice does not deepen, and that’s the big point, is that the voice doesn’t deepen, they retain sort of high… They retain a soprano singing voice, but they have a much larger body size. They have larger lungs, so they have a powerful soprano voice, more powerful than a female soprano voice. And females were not allowed in church choirs, so they needed men basically to fill those parts in the choirs, so that’s what castration did for them. But of course what happens is these men have almost no libido, and of course they have no ability to impregnate anybody.

So that is one of the ways, that’s one of the sources of information that castration, even in humans, lowers libido. So it’s something about the testicles is necessary for typical male libido. And this was also known because there was lots of castration experiments on animals and animals would be castrated to reduce aggression, to reduce libido for various reasons, to generate certain kinds of meat like from a chicken, a castrated chicken has a large body size and more tender meat, and that’s called The Capon. And so it’s been known for ages that castration of male animals reduces muscle mass, reduces and eliminates libido and aggression in some cases. Yeah, so there was a long, deep knowledge about the testicles and the necessity of the testicles for typical male behavior, but testosterone itself was not isolated until 1935. And so that took a long time because we’ve known about this since the fourth century BC, had this information and yeah, so it took until the early 20th century to really identify testosterone and start to try to manufacture it.

Brett McKay: Okay, so let’s talk about how testosterone makes boys boys and men men. And I think oftentimes we think, Oh, testosterone only has an effect on a male during puberty that’s when we have this huge spike, but you talk about the influence of testosterone starts in the womb prenatally. So walk us through that process, what happens to a fetus when it’s exposed to testosterone? What’s going on there?

Carole Hooven: Yeah, so that’s super important, that prenatal and directly postnatal period, we don’t know as much about what testosterone is doing in little boys, little boy babies when it goes up right after birth, but we can talk a little bit about that later, but we know a lot about what it’s doing in utero. And I should just say that the way that little humans or conceptuses, which are just that embryo, the very early embryo actually doesn’t become male or female because of testosterone, it takes on male and female characteristics because of testosterone, but the determination of male and female is dependent upon the presence of the Y chromosome and the gene on the Y chromosome, that is sex-determining region of the Y… Called sex-determining region of the Y-chromosome or SRY. So if you have the Y chromosome, and it has an intact SRY gene, which almost every male will have that. That is what causes the undifferentiated gonads to differentiate into testes. So before six weeks…

The embryo is not identifiable as male or female. You could look at the chromosomes, but there are no structures or physical differences yet, it’s when that gene is expressed, that it goes on to cause that tissue, those undifferentiated gonads to differentiate in the testes direction rather than the ovaries direction.

So once that happens, it just takes a couple of weeks for the testes to start pumping out testosterone. So, like, I was pregnant with a boy, and it was just bizarre to know that he was in there with his little testicles in my body, that his little balls are making testosterone, that and that testosterone is what was necessary for guiding his body and to promote the development of all the male reproductive structures and Physiology, so his scrotum, his penis, his prostate, his vas deferens… All that stuff is due to the actions of testosterone directly, and testosterone can do that because, like I said before, it acts on his genes that females share.

Females have the same genes, it’s just that they don’t have testosterone to cause the genes to be expressed in a way that grows and maintains the male reproductive structures. So the little fetus has testes that produce a lot of testosterone, and that’s what is responsible for the development of the male reproductive structures and male reproductive function that I just described, but at the same time, evolution has done this amazing thing where testosterone at the same time, prenatally, as it’s working on the body to masculinize it, it goes into the brain, because, I’m just gonna say it knows that this is an animal that needs to reproduce in a way that females don’t need to reproduce. Like this animal has to compete basically for female mating opportunities and it’s gonna be producing sperm, so this animal is going to, as a little kid, need to be do more rough and tumble play, for instance, and females might have to practice nurturing behavior, so females don’t have exposure to testosterone in utero, or they have very… Typically, very, very low exposure.

Males will have high levels of… Very high levels of testosterone in utero that masculinize the body and the brain, so that the brain can take advantage of the male body and shape that animal for male reproductive strategies, which are different than what females need, because females need to use their bodies to grow their offspring and feed their offspring… Sorry, offspring, and males don’t use their bodies to grow the offspring, they use their bodies to compete for the right to make… To have a female do the work for them basically, and that all starts in utero. And then there’s a small rise in testosterone… Sorry, it’s… Actually, it’s a short-term rise, it’s a three-month increase in testosterone shortly after birth that seems to be very important physically, again, and probably neurologically, but we don’t know a lot about it, but there are some hints that it might have to do… Might further masculinize behavior, and have something to do with penis development and could have something to do with ultimately penis size, but there’s not a huge amount of work on that yet…

Brett McKay: Right. So okay, basically, this is kinda like a mini puberty for boys right after they’re born.

Carole Hooven: That’s right. That’s right.

Brett McKay: We’re gonna take a quick break for words from our sponsors. And now back to the show. So basically, this prenatal exposure testosterone, is it kind of laying the ground work, like the wiring for later development in puberty?

Carole Hooven: That’s exactly right. So the framework that scientists use to talk about this is called the organizational activation effect or framework. So this is the idea, and this is actually really important because people think all you have to do is shoot up, and this happens obviously in, like trans men, or people who transition their gender, they will take the hormone, they’ll block their own hormones and take the hormones of the opposite sex. So for instance, if a female transitions to live as a male, and takes male levels of testosterone, that testosterone that she’s taking as an adult is acting on her brain, in a way that’s different from how it would act on a male brain, because a male brain has been… The neural structures are permanently masculinized, and these are very subtle effects, these aren’t huge differences in structures in the brain.

These are widespread small effects on, like cell death and synaptic, and connections between cells, so these are small effects that seem to have… Small changes that seem to have important effects in adulthood. So the brain is masculinized in boys pre-natally and then in adulthood when testosterone goes up in puberty, that testosterone is acting on those previously masculinized neural structures. So that if testosterone goes up in adulthood, say in a female whose brain has not been masculinized pre-natally, it’s going to have a different effect because it’s not acting on previously masculinized structures. And, this is hard to study, in humans, but it’s very clear in non-human animals, that you cannot activate typical male sexual and aggressive behavior in female animals whose brains have not been masculinized pre-natally, if that makes sense.

Brett McKay: Yeah.

Carole Hooven: Does that make sense?

Brett McKay: Yeah. That makes sense, that makes sense. And so okay, this prenatal exposure testosterone is what gives boys their boyish behavior, so like… While these others…

Carole Hooven: Yeah, yeah, before puberty, they’re like tackling each other.

Brett McKay: Before puberty, Yeah, so there’s a lot of rough and tumble play, I think I’ve heard boys, this is generally tend to be more object-oriented as opposed to person-oriented. And what’s interesting, like gender differences in toy preferences. You see this even in chimps, they’ll give Chimps a toy and the female girl chimps will play with maybe a doll, but the boys will somehow turn it into a weapon or some sword.

Carole Hooven: Yeah, the primate toy studies are less… They’re interesting, but I…

Brett McKay: Not robust. Sure.

Carole Hooven: They are less convincing to me than the rough and tumble play, we don’t even need the toy thing. We need… You can just…

Brett McKay: Okay, just the rough housing.

Carole Hooven: Yeah, you can look at all these. Just look at, take mammals, and it’s not even confined to mammals, but you could look at chimps, you can look at rats, you can look at a huge variety of animals, and you look at the juveniles and there are clear sex differences in play that are parallel in many ways to what we see in humans where the male, the little boys, say in chimps or in rats are tackling each other, they’re playing physically, they are… What they’re doing is practicing physical competition for status as adults, so they have to practice their reproductive skills, their survival and reproductive skills.

So that rough and tumble play is fun, it has to be fun, or else they wouldn’t do it and they wouldn’t get the practice, but they like that heavy physical play more than females do. Females are doing other things. And in humans, we see the exact same patterns. And in non-human animals, you can easily manipulate the expression of that behavior by simply suppressing testosterone exposure in boys, or increasing prenatal testosterone exposure in females and female juveniles in non-human animals, you can… It looks like it’s entirely due to prenatal testosterone exposure. And then in humans, first of all, we have a very large and cross-culturally consistent sex difference where boys like to play physically. Now, I’ve…

Again, I have a son, he has friends who are female, I know how they play. I don’t see girls getting together in groups and jumping all over each other for hours, like boys will tend… On average, not everyone does this, and there’s overlap in these complex behaviors, but these are broad patterns. And there’s a suggestion in humans that it’s also apparently, of course, the cultural influences, but that testosterone is the primary driver, because we know in girls who have different conditions, especially congenital adrenal hyperplasia, that result in their exposure prenatally to abnormally high levels of testosterone. So it’s not as high as boys, but even a slight elevation in girls can have a pronounced masculinizing effect.

And so girls that have this condition where their… It happens to be their adrenal gland is producing relatively high levels of testosterone, that condition is corrected at birth at least in places with good medical care, and those girls on average, end up far more than girls who don’t have that condition to want to engage in rough and tumble play, they wanna play with whatever toys the boys are playing with, they’re more likely to wanna play with boys, they’re more likely to grow up to be lesbians, they’re more likely, even though the rates are very low, to have a male gender identity than females who never had that condition. And the only difference there is that they had increased exposure to testosterone in utero, there’s no difference in the adult hormones.

So it’s clear that that sex differences in that early exposure to testosterone have a huge amount to do with who we become, because this is prior to puberty. So if boys are engaging more physically active basically, especially with each other, in childhood, that’s gonna set the stage for later behaviors, almost regardless of what happens in puberty. And this is not all boys, I should say that boys who grow up to be gay are much less likely to engage in rough and tumble play, but those boys… So that’s interesting, and that’s kind of a mystery, but those boys who grow up to be gay have the same pattern of sexual behavior of boys who grow up to be heterosexual. So being exposed to high levels of testosterone in utero seems to always shape male sexual behavior to be masculine, to shape the desire for a higher number of sex partners ultimately and a higher libido.

Brett McKay: Okay, so we’ve talked about childhood, so prenatal testosterone raise the ground work throughout childhood, T levels between males and females are pretty much the same, and then puberty happens and there’s this spike. And I think we all know what happens during puberty, the secondary sex characteristic just show up, you get taller, more muscle mass for men, body hair, facial hair, deeper voice. What’s going on though on the brain, how is that testosterone surge influencing the mind and behavior?

Carole Hooven: I’ve talked to a lot at this point, just in talking about the book, a lot of men and trans men, which is interesting, people who lived as women and then took high levels of testosterone about what it feels like. Most men say that they were preoccupied with sex, preoccupied with their position in the status hierarchy and social relationships among boys, and then young men. So again, I have this 12-year-old, and that’s what he talks about a lot, he’s… Not the sex part, but the who is popular, what they do, how they behave. And this is all fascinating because it seems all of them are really, really attuned to status hierarchies, and there’s a great evolutionary reason for that, and testosterone is promoting that.

Girls have their own hierarchies too, that’s also extremely important, but the way they navigate competition within those hierarchies is totally different. Girls don’t use this very direct form of aggression and physical aggression, they tend to use gossip and passive aggression and back-stabbing, I hate to say. And now social media, which I think that’s a horrible way to harm people’s reputations. Boys are more likely to go up into somebody’s face and call them an a-hole or something, and so they’re this… And they’re more likely to get into obviously physical aggressive… Physically aggressive interactions, and of course, that depends on culture around the world, and just within, say our United States, there’s obviously different norms around beating other guys up with different cultures.

Brett McKay: And I think there is a point…

Carole Hooven: So, Yeah. I think that’s what’s going on psychologically is sex and status competition.

Brett McKay: And I think a point to make is, there is a cultural… So we have this biological thing going on, but culture can help direct it, right? So in the west, it’s like, Well, how do you get status? It’s like, Well, you go maybe you play football, or you run for student council, or… This is if you were a teenage boy.

Carole Hooven: That’s right.

Brett McKay: You can get status that way. In another culture, it might be something different, but they’ll be a drive for status somehow.

Carole Hooven: Exactly.

Brett McKay: Because the idea is like, if you got status, the chicks will like you.

Carole Hooven: Yeah, but you might not even think of it that way at the time. You just seem driven to gain status over other boys or young men. And yeah, it seems like a benefit is that the girls start to pay attention to you. So, culture… People sort of miss this point about how incredibly important culture is. And nobody should resist the facts of biology about… And the role in all of these types of behaviors, they shouldn’t resist that because they think that culture is important or culture is more important. It’s incredibly important. But what’s interesting is how it interacts with our biology in these fascinating ways that have an important evolutionary explanation.

Brett McKay: Well, I think you made some guy, I forgot who is was, I think the guy that wrote, The Trouble With Testosterone. I forgot his tame.

Carole Hooven: Robert Sapolsky.

Brett McKay: Yeah, he said, like, if you… Talking about the influence of culture and biology, kind of the interplay they have. It’s like, if you gave testosterone to a bunch of monks, they would start competing… They wouldn’t start beating each other up, they would start trying to out compete each other, who can meditate the most or who can do niceness…

Carole Hooven: The niceness or something, yeah.

Brett McKay: But if you gave testosterone to a prison gang.

Carole Hooven: That’s right.

Brett McKay: You’d probably see just a bunch of shanks and things like that.

Carole Hooven: Yeah, that’s what’s fascinating is that, it seems to promote whatever is necessary for a man, and or an animal in a given environment to gain status or to avoid… Just to avoid losing status, say. So, it sort of increases your attention to those signals of status is how it seems to work. Your vigilance and your attention and your striving for status in whatever way is necessary. And in our deep history and still in many parts of the world, that was physical aggression. So that’s why males are larger than females and still are, so there’s still those cues and women are still attracted to big, tall, say, muscular, assertive men. Even if there isn’t any actual reproductive benefit. That’s how women are wired. So males are also still wired to, Yeah, really care about status and be responsive to those cues, in a way that women are responsive to different kinds of cues. And status just is not quite as important for female reproduction, of course, as it is for men. It still matters because females wanna compete for the high status males, and there aren’t that many of them, so.

Brett McKay: Let’s continue with this status-strain here. So I think it’s interesting, you talk about studies that testosterone can… Okay, influences this drive for status chronically, systemically, so, it just kind of wires you for that. But there’s these acute things going on. If a male experiences an increase in status or a decrease in status, there can be these sudden drops of testosterone or increases in testosterone. What causes such a rapid change? ‘Cause I mean, the production of testosterone takes a while. It has the pituitary gland sent a signal and…

Carole Hooven: Very good, very good.

Brett McKay: What causes that super fast? It’s so weird. A guy can watch his favorite sports team lose, and his T-levels will drop immediately. What’s going on there?

Carole Hooven: Yeah. So I don’t wanna overstate the prevalence of this phenomenon. And however, it does exist in humans and in non-human animals. And I think it’ll be helpful just to say what happens in non-human animals. And so the Syrian hamster has been studied heavily regarding these testosterone changes, which I think are very important in humans. And again, it’s not so much how much testosterone you have as a guy in general, as long as it’s within the normal range, your sort of baseline level seems not to be super predictive of much. What does, to me seem to be important is prenatal testosterone and these changes that you’re talking about in social… That are a product of social interactions. And this to me, is absolutely fascinating. So in Syrian hamsters, if a Syrian hamster has a fight with another male for territory… So territory is the equivalent of any kind of resource in humans, ’cause you need territory to get females, ’cause females will feed on the territory that a male can guard, basically. So high status males will have larger territories in the wild, anyway. And the outcome of… If you think about it from an evolutionary point of view, or even think about it from today.

So if you’re fighting physically with another guy, if you lose, you need to know on some level that you’re a loser. You can’t go… If you’re losing consistently against other males in physical competitions, you need to stop, you need to run away, basically. [chuckle] If somebody’s in your face, you need to run away, you shouldn’t be challenging them. ‘Cause you wanna survive to try to win some other competition in the future, so that you can mate, right? So how do animals make those decisions about… How do they know, “Well, I need to fight,” or, “I need to flee,” right? Those are decisions that animals have to make. So when you’re… When someone’s threatening you, it may trigger in you the feeling that they’re threatening you physically, even if it’s just a chess game or a tennis match, definitely in a football game or just some guy is in your face, there’s all kinds of situations where two males are competing for status in humans, in some way, right?

So in the hamsters, if a male loses a physical fight and he submits, right? He ends up by getting on his back and submitting, his testosterone will tank. So first of all, when they’re facing off, they’re both of them have an increase in testosterone, the loser will have a pronounced decrease in testosterone. The winner will maintain high testosterone or it will get higher. And if you… And then the loser will fail to defend itself or defend it’s territory against a future threat, because he’s lost… That reduction in testosterone is somehow telling him, He should be scared and run away.

So if you block that reduction in testosterone after he loses, he’ll continue to defend his territory and challenge other males. And then he’ll get his ass kicked and he could die, right? So it seems like the testosterone drop is adaptive for losers. A testosterone rise is adaptive for winners. Because it’s a way of, signaling, shaping, the animal for future encounters. So if you’re a winner, you know in the face of threat that you’re a winner. You act like a winner, you don’t back down. You take on the challenge. If you have lost, you’re fearful and anxious and you retreat from confrontation. So we have all varieties in humans of those responses to competition, but it seems like testosterone changes in the moment in the face of competition are playing a role neurologically to set people up for reaction to future competitions and may help to account for different… Even in the ways that people engage in competition in general.

And just feeling like, they are fearful or feeling confident in the face of competition. So yes, there’s all kinds of examples in the human literature where either from sports, or again, from competitions that are not physical even. And then there’s all these competitions that we don’t measure, which are just males getting in each other’s faces in some way. Having subtle competitions where there are these testosterone changes. It’s tough to pin down experimentally, exactly when they happen, and who they happen in, and exactly what the function is. But from the literature on non-human animals, it seems clear that we do know that when testosterone rises in these social situations, it can increase dopamine, which is a hormone that is rewarding, and promotes the same behavior in the future, because… It increases motivation for the same behavior in the future because it felt good last time. And cortisol is a hormone that is associated with stress and anxiety and that can be paired with the testosterone drop and that can possibly motivate the animal more towards a retreat-strategy in the future.

Brett McKay: So, there’s like a Matthew effect going on, right? To he who has, will be given more, he who doesn’t have will be taken away from. So.

Carole Hooven: Yes.

Brett McKay: Yeah.

Carole Hooven: I think that’s right, but it’s adaptive for all basically based on… But it’s a way to… If you’re in a stressful situation, it’s possibly a way to condition males about how to respond very quickly, so they don’t have to stop and think about it. And I should just say you raise a really interesting question, how does testosterone change in these situations, because like you said, the signal to produce testosterone in the testes comes from the brain. It comes from the hypothalamus and pituitary in the form of luteinizing hormone, and it takes an hour for that hormone to get from the brain to the testicles and to result in a pulse of testosterone, essentially. Then that testosterone have to go through the blood and alter gene transcription, which theoretically should not have immediate effects on behavior. So the answer is we don’t know how social interactions can cause these testosterone rises. It may be that it’s not coming from the testes or it may be that it’s not coming from LH… Luteinizing Hormone. It may be that there’s an increase in adrenaline, and that somehow adrenaline acts on the testes to release testosterone that’s kind of hanging out there, but we don’t know.

Brett McKay: Right.

Carole Hooven: And this is something that I’ve been obsessed with a long time. What is the mechanism here?

Brett McKay: Okay, so testosterone makes a boy… Or teenage boys, young adults, young adult males preoccupied with sex, preoccupied with status. We also talked…

Carole Hooven: I wouldn’t say makes but heavily influence. Heavily influence, yeah.

Brett McKay: Heavily influence. [chuckle] Yeah. Right. But… And then also, we’ve talked about this a little bit, aggression. It makes or causes or influences males to be more aggressive. And what’s the advantage of… What’s the advantage of being aggressive, because that just helps you get access to mates and resources? Is that the idea?

Carole Hooven: So there’s actually not a big sex difference in aggression just broadly. It’s really physical aggression.

Brett McKay: Okay. Physical aggression.

Carole Hooven: So using… And what’s interesting is, if you think about these strategies over human evolutionary history that males and females would use to maximize their reproduction. And that’s what natural and sexual selection acts on, is the traits that animals possess that allow them to maximize reproduction. So for females, taking physical risks is a bad idea because you need your physical integrity. You need energy, you need safety, you need a long healthy life. That’s what… Because you don’t have to worry about fighting for mates, right? You have to worry about having the energy and health that you need to bear and feed your children, and you have to care for them.

So it doesn’t pay off for females to take physical risks. And they don’t have that need to compete physically for mates. Although they compete for mates, but in ways that don’t put their physical selves at risk, typically, right? So males are, relative to females, over evolutionary history have benefited from physical aggression, because that’s what their bodies are, in a sense, built to do, relative to females. That’s where they’re putting their reproductive energy budget. That’s why they have bigger bodies and more muscle. That’s the only reason, relative to females. So that muscle, that’s a history of using their bodies to compete physically for mates. So we retain that in a modern environment… And that’s… Again, that’s attractive to females. It’s not the case that they have to compete physically anymore. So in different cultures, women are gonna prefer men who have high status, whether it’s gained physically or not. I’m married to a philosophy professor and he’s definitely never gotten into a fight, but he’s super attractive to me, partly because, partly because of his status, but it’s not, he got that with his brain, not with his body, but it depends on the environment you’re in and what pays off. So we have this evolutionary history of physical aggression paying off, but it still plays out in the extremes.

Brett McKay: Yeah, you can see the propensity for physical aggression in males, just like looking at crime reports.

Carole Hooven: That’s right.

Brett McKay: If you look at murders, physical assault, sexual assault, it’s pretty much all dudes. There’s women there every now and then, but it’s mostly dudes, but then if you look at crimes like fraud, shoplifting, etcetera. There’s still more men, but women, that’s more of where they do their crime, if they’re gonna commit crimes.

Carole Hooven: Yeah, that’s where the sex difference is reduced, so women are gonna commit crimes, but they’re just much less likely to put themselves physically at risk to commit those crimes. Males are much more likely to put themselves physically at risk to commit crimes and to do everything else, to show off, to thrill-seeking, men are just far more likely to do that physically.

Brett McKay: Okay let’s, so we’ve talked about testosterone’s effect on behavior in males. Something that’s been getting a lot of press lately is the role of testosterone in athletic performance. What do we know what’s going on there?

Carole Hooven: So there’s a lot of controversy and confusion around this area, but I’ll just say that the science is clear. It’s not confusing, and people who try to make it seem confusing, from my point of view, have a political or ideological agenda. It’s totally clear that in the almost all sports, there are some exceptions, males, men, so if you’re looking at the elite level, if you’re looking at comparing highly trained people who are all taking care of themselves, all healthy, eating well, sleeping, training, etcetera, men blow women out of the water. There is no competition. There are, in many sports, even at the Olympic level, there will be thousands of men who will be better than the number one female, and that’s almost the case across the board. In some endurance sports, there are some exceptions to that.

The reason is testosterone. It is, again, this is abundantly clear that this is an effect, a consequence of males going through puberty, for all the reasons that… All the things we’ve been talking about physically, never mind what might be happening psychologically, which is a question, but the physical advantages are immense in terms of what happens that is irreversible, first of all, in puberty. So there is some aspects of pubertal changes that are reversible, but there’s others that are not.

So the ones that are permanent are obviously the bone growth, so the height, bone density to some extent is irreversible. Testosterone causes increase in bone density, and that happens because of the increased muscle during puberty that exerts forces on the developing bones that causes them to increase mineralization and density. So you have stronger, taller bones. So you have larger bodies, and on those larger bodies have much more muscle and testosterone causes stem cells during puberty to differentiate into muscle preferentially over fat. So those don’t reverse, so that in adulthood, if you suppress… If you’re a man, and a male and you suppress your testosterone, you will not lose all of that muscle advantage you would have over a typical female.

So there’s height, there’s bone density, there’s larger hearts and lungs, there’s increased hemoglobin. So males have significantly more hemoglobin. That’s a direct effect of testosterone and hemoglobin carries oxygen around the blood, so you’ll have more oxygen fueling the greater amount of muscle mass. You have massively higher upper body strength. Males, again, the upper body strength just blows away the upper body strength of females. You have greater throwing capacity. You have greater grip capacity. I could go on and on. And you have more power. So sports that emphasize power, like weight lifting.

Like Laurel Hubbard, for instance, is a trans woman who competed in weightlifting in the Olympics recently, and there was a lot of controversy and questions about whether she, because she was a person who was male who transitioned to living as a woman and had stopped her testosterone and taken estrogen and the question was would she have an advantage in weight-lifting over natal women? And the answer is yes. Because she went through male puberty, she’s going to have a huge advantage because all of her muscle mass that she gained as a result of male puberty doesn’t disappear even when testosterone has stopped for something like even five years. So there’s enormous advantages to going through male puberty and those do not disappear when testosterone is suppressed in trans women. And that’s just indisputable. There’s just no, it’s not that women, some people are saying women aren’t trying hard enough and that’s why they’re losing. That’s just a joke. That is a joke.

Brett McKay: So when people finish this book, what do you hope they walk away thinking?

Carole Hooven: Yeah, there’s a couple of things. Of course, I’m incredibly interested in testosterone and the power of testosterone and how it shapes who we are, but I think one of my overarching values in life is that science and knowledge is, it’s crucial for us to have clear views about reality and to not fear the truth, and to do whatever we can to find and communicate the truth. That’s what I see my job as a science educator, and that when you learn how things work, you have more power to make the world a better, safer, more equitable place. And so that is one thing I want people to come away with. I want them to see that it’s possible to be clear and honest and open, but also sensitive and compassionate.

And then the other point is of course about the hormone. There’s just so much evidence that this one molecule shapes our society in these really profound ways and that the more we understand about how it works, the more we can capitalize on the positive aspects of being a man, which we didn’t even talk about. We didn’t talk about toxic masculinity, which I really don’t like at all. I don’t like that term. I don’t want my boy…

Brett McKay: I don’t like the concept either.

Carole Hooven: I don’t want him to be exposed to that idea. He already is, and I don’t like that at all. I want him to be, I’m tearing up here. I want him to be proud. Sorry.

Brett McKay: No, it’s fine.

Carole Hooven: Sorry. I feel so deeply about this. Nobody should be ashamed to be a man, to be masculine, and we didn’t talk about heroism, and if you look at the news and who’s risking their lives to save the lives of others, it’s men, typically. There are really brave women who are doing that too, but over, I don’t know why I’m getting so upset. I’m sorry.

Brett McKay: No, you’re fine.

Carole Hooven: It’s men, and I think there are a lot of struggles that we need to acknowledge that men are facing, and I wish we could just be open, and some of those struggles are around puberty and adolescents and I wish that more people felt they could talk about their struggles and have support, and that this ultimately is the way to making the world a better place, and there’s so much positivity around masculinity and that should be celebrated and encouraged, and this whole narrative about toxic masculinity that seems to be increasing, I wish would end. I wish it would end.

Brett McKay: No, I think that’s a… I like how we ended on that ’cause I think it’s true. I’m tired of the toxic masculinity discourse. I don’t think it’s helpful. I don’t even know what it means anymore ’cause it gets banded around so much, but then we also forget about all the great things men do, and I think that’s, I think men need to hear that as well ’cause I think you’re just scolded all the time in the popular culture and it can get you down.

Carole Hooven: Yeah, and you’re… I assume working hard and being a great dad. To me, having that involvement in the family and having that kind of support and men bring something to the family that women just don’t. And I watch this in my own family, the way that I am with my son and the way my husband is with my son is very different and he needs that. I’m not saying that people won’t, that every family has to have a male and a female, or a mom and a dad, ’cause of course, they don’t, but there is something that is so important that dads are bringing to the family, and also I have, the people aren’t gonna like this, but to the world, there is a different way of being in the world that I’ll just say quickly.

That I asked my students at the end of class, I usually ask them, what would the world be like without men or something like that, and just a couple years ago a student said, “I don’t think we’d have tall buildings.” Or I think I said, “What would happen if we castrated men?” or some other student said, “We should castrate all men” or something ridiculous, and this other student spoke up, which was great. I don’t think he’d say that today. He said, “I don’t think we’d have tall buildings. I don’t think we’d have the kind of innovations that we have,” and that’s controversial, of course, but there is something to it. That competitiveness, that drive for status sometimes can be destructive, but can also be incredible motivation for innovation, and that’s something that remains to be explored. It’s too politically incorrect probably to study it seriously, but I wish we could.

Brett McKay: Well Carole, this has been a great conversation. Where can people go to learn more about the book and your work?

Carole Hooven: Okay, so I have a website, I’m on Twitter @Hoovlet, H-O-O-V-L-E-T, and my book is on Amazon and wherever you like to get your books, and if you do get it and like it, I never ask people to do this, I keep forgetting. Just if you could review it on Amazon, that really helps. And yeah, so I’d like to get more reviews.

Brett McKay: Fantastic. Well Carole Hooven, thanks for your time. It’s been a pleasure.

Carole Hooven: Thank you so much, Brett. I’ve enjoyed the conversation.

Brett McKay: My guest today was Carole Hooven. She’s the author of the book; T, The Story of Testosterone. It’s available at and book stores everywhere. You can find out more information about her work at her website, Also check out our show notes at AOM.IS/T where you can find links to resources, where you can delve deeper into this topic.

Well, that wraps up another edition of The AOM Podcast. Make sure to check out our website at, where you can find our podcast archives as well as thousands of articles written over the years about pretty much anything you can think of, and if you’d like to enjoy ad free episodes of AOM Podcast, you can do so on Stitcher Premium. Head over to Sign up, use code Manliness at check out for a free month trial. Once you’re signed up, download this to your app on Android or iOS and you can start enjoying ad free episodes of The AOM podcast. And if you haven’t done so already, I’d appreciate it if you take one minute to give us a review on Apple Podcast or Stitcher. It helps out a lot. If you’ve done that already, thank you. Please consider sharing the show with a friend or family member who you’d think would get something out of it. As always, thank you for the continued support. Until next time this is Brett McKay reminding you to not only listen to AOM Podcast, but put what you’ve heard into action.


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