Dr. Carol Hooven is a Harvard biologist and the author of Tea: The Story of Testosterone, The Hormone That Dominates and Divides Us. In this episode, Dr. Hooven explains the arguments that are made against testosterone s influence on shaping men into men, and why she doesn t think they hold up. 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.
00:00:00.560Hey, this is Brett. We're taking a break this week from new episodes to celebrate the holidays and rest and relax, but we're going to rebroadcast episode number 761, How Testosterone Makes Men, Men, with Dr. Carol Hooven. Hope you enjoy it, and we'll see you next week with a brand new episode.
00:00:23.140Brett McKay here, and welcome to another edition of the Art of Manliness podcast. What creates the differences between the sexes?
00:00:30.000Now, 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.
00:00:43.080Her name is Dr. Carol Hooven. She's a Harvard biologist and the author of Tea, The Story of Testosterone, The Hormone That Dominates and Divides Us.
00:00:49.780Today on the show, Carol explains the arguments that are made against testosterone's influence on shaping men into men and why she doesn't think they hold water.
00:00:56.560She 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.
00:01:04.020We delve into where tea 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.
00:01:12.680We then discuss how tea shapes males starting in the womb and going into puberty and beyond before turning to its influence in athletic performance.
00:01:19.420And we enter a conversation with Carol's impassioned plea for celebrating what's great about men.
00:01:24.120After the show's over, check out our show notes at aom.is slash tea.
00:02:11.740I 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.
00:02:19.140And 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.
00:02:29.820And I read this book by Richard Wrangham called Demonic Males.
00:02:33.340And I had really been focusing in on understanding human behavior and I'd gotten really interested in neurobiology.
00:02:41.220Then I discovered genetics and evolution and got really interested in that.
00:02:45.160And 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.
00:03:27.940And 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.
00:03:40.580I 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.
00:03:49.340So 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.
00:04:02.940That got me really interested ultimately in testosterone because 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.
00:04:20.420Just in these very broad patterns of status and hierarchy obsession among the males competing, you know, largely for food and the right to have sex with the females who are in estrus, who can get pregnant.
00:04:36.880So there's a lot of aggression, there's a lot of status obsession in the males.
00:04:41.980They're also capable, you know, like humans are, of being kind and nurturing and warm and family oriented in a way.
00:04:50.960And the females, on the other hand, I never saw, although it does happen, I never saw any instances of female physical aggression.
00:05:00.000I saw it every single day among the males.
00:05:04.140And so that was just this very pronounced sex difference where there was a lot of nurturing and caregiving among the females, just much more peaceful overall on, you know, all of this is on average and they don't have any human culture.
00:05:19.100So there was nobody who was going to be able to convince me after that experience that these similar patterns of sex differences in humans are primarily due to human culture.
00:05:42.480And so that's why I got interested in testosterone because there's no more powerful way of explaining human sex differences, which are, you know, male behavior in particular is a really important aspect of our lives.
00:05:56.860One 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.
00:06:13.900I'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.
00:06:25.320So most critics, except for the most extreme ones, will acknowledge that the physical differences, basically from the neck down, are due to testosterone.
00:06:39.640So it really – you have to be kind of a nutjob to deny that male size and strength overall, although there are nutjobs who are getting a lot of press, unfortunately.
00:06:52.620But that's just really – it would be incredibly far-fetched to try to deny the science that testosterone at least explains the secondary sex differences in humans.
00:07:03.740So that's height, muscle mass, you know, fat distribution, body hair, those kinds of things.
00:07:11.180So most critics will acknowledge that testosterone is responsible for those physical differences.
00:07:15.700More reasonable critics – and I think, you know, 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 behavior, and that it is not ultimately sort of the most powerful driving force in those sex differences that I just talked about.
00:07:38.980So the largest sex differences that exist – and this is not my view, this is fact, I'm not talking about the cause, I'm just talking about the observation – are in sexual psychology and behavior and physical aggression.
00:07:52.280So those are huge, consistent with non-human animals.
00:07:55.700We see them across ages, not the sex part, but across cultures, you know, they're just incredibly pervasive.
00:08:03.060And 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?
00:08:20.140So 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, like around, you know, prenatally and directly postnatally, 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,
00:08:49.700including humans, including humans, including humans, to take advantage of their larger body size and the fact that they have sperm in a penis, that they have to be motivated to want to get that sperm into the female reproductive tract.
00:09:01.080And 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, you know, and that could be territory.
00:09:13.500Now it's 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.
00:09:27.300I mean, and there's different strategies that males can use, and we can get into that.
00:09:31.240So it might not be an increased number of sex partners, but it might be using one's body and having the psychology to want to use one's body, or even just one's sort of competitiveness and desire to elevate one's status.
00:09:47.160That 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.
00:09:57.020It doesn't mean that you have to have 10 kids, but it means you have to acquire that mate and have sex with her.
00:10:03.680So 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.
00:10:19.540But sorry, this is a long answer, but the idea is that testosterone coordinates the psychological adaptations with the physical adaptations.
00:10:28.460And I should just get back to the critics, because 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.
00:10:42.540Because 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.
00:10:54.260But this just doesn't make sense from a scientific and evolutionary point of view.
00:10:59.880The default assumption is that we are like, you know, all of these other animals, where testosterone does these very same things in males.
00:11:07.780It's not a coincidence that it does the same thing in humans.
00:11:11.960It'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.
00:11:22.220So it's always gene, so it's always gene-culture interactions.
00:11:26.100Why do you think the critics are so reluctant to embrace the fact that T influences not just the body, but the mind?
00:11:32.160Like, what is, like, the apprehension?
00:11:34.180Yeah, I think it's based on fear, which should not be playing a role in science and our efforts to understand reality.
00:11:44.760So 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.
00:12:12.820Then we're stuck with bad male behavior, and it justifies bad male behavior because it's natural.
00:12:20.400That's called the naturalistic fallacy, by the way, the idea that what is found in nature is good.
00:12:25.920You know, anyone can see in two seconds that there's plenty of things that are natural, like malaria, that are terrible.
00:12:32.820So 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.
00:12:48.480And 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 murder are, because males commit across the world about 95 to 98% of all murders.
00:13:07.120But in some cultures, the sex difference in the murder rate and the murder rate itself is incredibly low.
00:13:14.040And I always use Singapore as an example because it's extremely safe.
00:13:18.900People, especially women, can walk around feeling safe because the sexual assault is incredibly low.
00:13:26.400You know, physical aggression committed by males in general is extremely low.
00:13:30.740And that's because of their culture and harsh penalties for those crimes.
00:13:37.240And we know that there are examples on the other end, like I was just talking to a grad student in my department who is from India, and he was, and I, you know, know the data on India, but sexual assault is rampant because it hasn't been taken seriously in India by the government there and there, you know, you can get away with it.
00:13:57.980And so men, if you can get away with it, men are going to do it, and they do.
00:14:01.280So the idea is that genes and testosterone sort of lower the bar for the expression of those behaviors in the right environmental circumstances.
00:14:13.040But that doesn't mean that the environment can't shape heavily the expression of those behaviors, right?
00:14:19.860So 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.
00:14:28.200And that's clear from just even looking across cultures or even across time and how we've changed over time.
00:14:34.160Our genes haven't changed, but the laws have and that social norms have.
00:14:38.360Okay, let's dig into the basics of testosterone.
00:14:41.060I think everyone has a general idea what it is.
00:14:44.320It's a male, all male and females have testosterone, but males have more testosterone.
00:14:50.180Kind of like where is it made in the body and like what are the difference in testosterone levels in men and women?
00:14:55.740So testosterone, first of all, in adulthood, males have anywhere, in puberty, males can have 10 to 30 times the level of testosterone as women.
00:15:06.800But in Western kind of well-fed populations, males have about 10 to 20 times as much as females, adults, that is.
00:15:17.360And there's no overlap in testosterone levels in healthy, normal populations of men and women.
00:15:24.680And 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.
00:15:38.200Testosterone is actually made by many tissues.
00:16:23.040And males who have more body fat are going to have more of the enzyme, which is called aromatase, that converts testosterone into estrogen.
00:16:32.020So men who have a high level of adiposity can start to develop some feminine features like gynecomastia, aka man boobs.
00:16:41.360And that's because the estrogen levels can really rise due to this high activity of this aromatase enzyme.
00:16:49.620So 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.
00:17:05.300And I should just say that testosterone is an androgen and there are different androgens in our bodies.
00:17:10.800Testosterone is the main one, but there are other ones like dihydrotestosterone, which is also a product of testosterone conversion.
00:17:20.020And all the androgens interact with what's the androgen receptor and like a key in a lock, basically.
00:17:27.520And the androgen receptor is present in many, many tissues, again, also in our nervous system, in our brain.
00:17:33.300And 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.
00:17:51.740They can just cross the blood-brain barrier.
00:17:53.840They can get right through cell membranes, inside cells, and they affect gene transcription once they're inside cells.
00:18:01.000So they're very, very powerful, and they can go everywhere and have these long-term systemic effects on us.
00:18:09.160I think it's interesting to note that our knowledge of testosterone is relatively new.
00:18:13.860It wasn't until the 1920s that scientists are able to actually pin down testosterone, the hormone.
00:18:19.980But before that, scientists, people, humanity had a hunch that the testicles were involved in masculizing men.
00:18:29.020And there's some interesting, like, I guess we call them, you know, 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.
00:18:41.740And one of them is this really interesting thing is in Italy, church choirs would castrate young boys, basically, they call the castrati.
00:18:55.880I do talk a lot about castration in the book over the ages and in different cultures, and I learned a tremendous amount.
00:19:02.740And it was all gross because I did get—it's not funny.
00:19:08.380I did get into the procedure, and there's also eunuchs in imperial China, and the way that they were castrated was particularly horrific.
00:19:19.860But most of the history of castration, so if we just start with the castrati in, say, 18th century Italy, these are—this—what happened was there was a lot of poverty, and there were opportunities for kids who were pre-pubertal, who were singers, to gain, you know, fame and fortune by singing in church choirs.
00:19:46.340I mean, 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.
00:19:55.540And 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.
00:20:04.220And 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.
00:20:16.160So 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.
00:20:37.680You know, some people start going bald fairly soon after puberty, but a eunuch never goes bald.
00:20:44.380And 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.
00:21:01.020So it's—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.
00:21:22.840And that is why growth—the height spurt stops at the end of puberty—it's actually because of estrogen coming from testosterone, even in boys.
00:21:32.160But the point is, if you remove the testes, you never have that testosterone increase during puberty, and that growth hormone generated childhood growth.
00:21:43.440Like, I have a 12-year-old boy, he's still in that sort of growth hormone period.
00:21:48.460He's transitioning now to testosterone, he's going to be taking over, and—but that period is extended.
00:21:55.380So 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.
00:22:08.020So they can be very tall, and they don't get those secondary sex characteristics that most of your listeners will have developed during puberty.
00:22:15.820So they retain their head hair, their voice does not deepen, and that's the—that's the big point, is that the voice doesn't deepen.
00:22:24.400They retain a sort of high—they retain a soprano singing voice, but they have a much larger body size.
00:22:34.320So they have a powerful soprano voice, more powerful than a female soprano voice.
00:22:40.700And females were not allowed in church choirs, so they needed men, basically, to fill those parts in the choirs.
00:22:48.500So that's what castration did for them.
00:22:51.260But, of course, what happens is these men have almost no libido, and, of course, they have no ability to impregnate anybody.
00:23:00.200So that is one of the ways, that's one of the sources of information that castration, even in humans, lowers libido.
00:23:08.860So it's something about the testicles is necessary for typical male libido.
00:23:15.480And 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, you know, generate certain kinds of meat.
00:23:30.340Like, like, from a chicken, a castrated chicken has a large body size and more tender meat, and that's called a capon.
00:23:37.160And so it's been known for ages that castration of male animals reduces muscle mass, reduces and eliminates libido and aggression in some cases.
00:23:48.760Yeah, so there was a long, deep knowledge about the testicles and the necessity of the testicles for sort of typical male behavior.
00:23:59.500But testosterone itself was not isolated until 1935.
00:24:03.600And so that took a long time, because we've known about this since, like, the 4th century BC, had this information.
00:24:11.140And, yeah, so it took until the early 20th century to really identify testosterone and start to try to manufacture it.
00:24:19.240Okay, so let's talk about, like, how testosterone makes boys boys and men men.
00:24:25.340And I think oftentimes we think, oh, testosterone only has an effect on a male during puberty, because that's when you have this huge spike.
00:24:32.160But you talk about it's, that, the influence of testosterone starts in the womb, prenatally.
00:24:44.840Yeah, so that's super important, that prenatal and directly postnatal period.
00:24:50.640We don't know as much about what testosterone is doing in little boys, little boy babies, when it goes up right after birth.
00:24:57.980But we can talk a little bit about that later.
00:25:00.800But we know a lot about what it's doing in utero.
00:25:04.580And 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.
00:25:22.920It takes on male and female characteristics because of testosterone.
00:25:28.160But 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.
00:25:43.960So 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.
00:26:01.320So before six weeks, the embryo is not identifiable as male or female.
00:26:08.380You could look at the chromosomes, but there are no structures or physical differences yet.
00:26:13.400It'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.
00:26:27.040So once that happens, it just takes a couple weeks for the testes to start pumping out testosterone.
00:26:32.340So 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.
00:26:44.840And that testosterone is what was necessary for guiding his body and to promote the development of all the male reproductive structures and physiology.
00:26:57.160So his scrotum, his penis, his prostate, his vas deferens, all that stuff is due to the actions of testosterone directly.
00:27:07.660And testosterone can do that because, like I said before, it acts on his genes that females share.
00:27:18.800It'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.
00:27:27.520So 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.
00:27:41.620But 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 going to say, it knows that this is an animal that needs to reproduce in a way that females don't need to reproduce.
00:28:05.260Like, this animal has to compete, basically, for female mating opportunities and is going to be producing sperm.
00:28:11.020So this animal is going to, as a little kid, need to be, do more rough and tumble play, for instance.
00:28:17.500And females might have to practice nurturing behavior.
00:28:21.600So females don't have exposure to testosterone in utero, or they have very, typically very, very low exposure.
00:28:27.440Males 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, you know, which are different than what females need.
00:28:44.200Because females need to use their bodies to grow their offspring and feed their offspring, and males don't use their bodies to grow the offspring.
00:28:55.380They use their bodies to compete for the right to make, to have a female do the work for them, basically.
00:29:03.060And then there's a small rise in testosterone.
00:29:06.420Sorry, it's actually, it's a short-term rise.
00:29:10.120It's a three-month increase in testosterone shortly after birth that seems to be very important, physically, again, and probably neurologically.
00:29:23.700But there's 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.
00:29:35.260But there's not a huge amount of work on that yet.
00:29:38.540Right. So, okay, basically, there's kind of like a mini puberty for boys right after they're born.
00:29:44.320We're going to take a quick break for your words from our sponsors.
00:29:51.280So, basically, this prenatal exposure to testosterone, is it kind of laying the groundwork, like the wiring for later development in puberty?
00:30:10.440And this is actually really important because people think all you have to do is shoot up.
00:30:15.740And this happens, obviously, in, like, trans men or people who transition their gender.
00:30:21.080They will take the hormone, they'll block their own hormones and take the hormones of the opposite sex.
00:30:28.200So, 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.
00:30:46.060Because a male brain has been met, the neural structures are permanently masculinized.
00:30:51.360And these are very subtle, these are very subtle effects.
00:30:54.340These aren't, like, huge differences in structures in the brain.
00:30:57.360These are widespread, small effects on, like, cell death and synaptic and connections between cells.
00:31:06.280So, these are small effects that seem to have, small changes that seem to have important effects in adulthood.
00:31:12.660So, the brain is masculinized in boys prenatally.
00:31:16.780And then, in adulthood, when testosterone goes up in puberty, that testosterone is acting on those previously masculinized neural structures.
00:31:26.740So that if testosterone goes up in adulthood, say, in a female whose brain has not been masculinized prenatally, it's going to have a different effect because it's not acting on previously masculinized structures.
00:31:40.540And 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 prenatally, if that makes sense.
00:32:15.420Yeah, so there's a lot of rough and tumble play.
00:32:17.540I think I've heard boys, this is generally, tend to be more object-oriented as opposed to person-oriented.
00:32:24.600And what's interesting, like, gender differences in toy preferences, you see this even in chimps, they'll give chimps, you know, a toy, and the female girl chimps will, like, play with maybe, like, a doll, but, like, the boys will somehow turn it into, like, a weapon of some sort.
00:32:40.580Yeah, I mean, the primate toy studies are less…
00:32:47.540They're interesting, but they're less convincing to me than the rough and tumble play.
00:32:54.060Like, we don't even need the toy thing.
00:32:57.980Yeah, you can look at all these, just look at, take mammals, and it's not even confined to mammals.
00:33:01.840But 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're, you know, what they're doing is practicing physical competition for status as adults.
00:33:31.520So, they have to practice their reproductive skills, their survival and reproductive skills.
00:33:35.840So, that rough and tumble play is fun.
00:33:38.480It has to be fun, or else they wouldn't do it, and they wouldn't get the practice.
00:33:41.980But they like that heavy physical play more than females do.
00:33:46.220Females are doing other things, and in humans, we see the exact same patterns.
00:33:50.960And 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, in female juveniles, in non-human animals.
00:34:07.100You can, it looks like it's entirely due to prenatal testosterone exposure.
00:34:12.120And then in humans, first of all, we have a very large and cross-culturally consistent sex difference where boys like to play physically.
00:34:20.080You know, I've, again, I have a son, he has friends who are female, I know how they play.
00:34:25.000I don't see girls getting together in groups and jumping all over each other for hours.
00:34:30.380Like, boys will tend, you know, on average, not everyone does this, and there's overlap in these complex behaviors, but these are broad patterns.
00:34:39.100And there's a suggestion in humans that it's also apparently, of course, a cultural influences, but that testosterone is the primary driver.
00:34:47.520Because 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.
00:35:07.660And 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.
00:35:21.740And 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.
00:35:31.460They want to play with whatever toys the boys are playing with.
00:35:34.940They're more likely to want to play with boys.
00:35:36.840They're more likely to grow up to be lesbians.
00:35:39.720They're more likely, even though the rates are very low, to have a male gender identity than females who never had that condition.
00:35:47.180And the only difference there is that they had increased exposure to testosterone in utero.
00:35:51.940There's no difference in the adult hormones.
00:35:54.680So 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.
00:36:05.520So if boys are engaging, you know, more physically active, basically, especially with each other in childhood, that's going to set the stage for later behaviors, you know, almost regardless of what happens in puberty.
00:36:20.020I should say that boys who grow up to be gay are much less likely to engage in rough and tumble play.
00:36:27.260But those boys, so that's interesting, and that's kind of a mystery.
00:36:30.700But those boys who grow up to be gay have the same pattern of sexual behavior of boys who grow up to be heterosexual.
00:36:39.940So 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.
00:36:52.920Okay, so we've talked about childhood.
00:36:54.720So prenatal testosterone sort of lays the groundwork.
00:36:57.240Throughout childhood, T levels between males and females are pretty much the same.
00:37:01.580And then puberty happens, and there's this spike.
00:37:03.580And I think we all know what happens during puberty.
00:37:05.000Like the secondary sex characteristics show up.
00:37:07.620You get taller, more muscle mass for men, body hair, facial hair, deeper voice.
00:37:13.200What's going on, though, on the brain?
00:37:14.800Like how is that testosterone surge influencing the mind and behavior?
00:37:18.840I've talked to a lot at this point, just in talking about the book, a lot of men, and trans men, which is interesting, you know, people who lived as women and then took high levels of testosterone, about what it feels like.
00:37:31.360Most 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.
00:37:44.380So, again, you know, I have this 12-year-old, and that's what he talks about a lot.
00:37:48.100He's not the sex part, but the who is popular, what they do, how they behave.
00:37:53.680And this is all fascinating because it seems all of them are really, really attuned to status hierarchies.
00:38:00.280You know, and there's a great evolutionary reason for that, and testosterone is promoting that.
00:38:05.200Girls have their own hierarchies, too.
00:38:09.100But the way they navigate competition within those hierarchies is totally different.
00:38:14.340Girls don't use this, like, very direct form of aggression and physical aggression.
00:38:18.820They tend to use gossip and passive aggression and backstabbing, I hate to say, and now social media, which I think that's a horrible way to harm people's reputations.
00:38:28.740Boys are more likely to go up into somebody's face and call them an a-hole or something.
00:38:32.660And so, they're more likely to get into, obviously, physically aggressive interactions.
00:38:39.740And, of course, that depends on culture around the world and just within, say, our United States.
00:38:45.920Like, there's obviously different norms around beating other guys up in different cultures.
00:38:53.500So, yeah, I think that's what's going on psychologically is sex and status competition.
00:38:58.600And I think a point to make is, like, there is a cultural, like, so we have this biological thing going on, but, like, culture can kind of direct it, right?
00:39:05.820So, in the West, it's like, well, how do you get status?
00:39:08.960It's like, well, maybe you play football or you run for student council or it's like if you're a teenage boy.
00:40:18.480Yeah, he said, like, if you, talking about the influence of culture and biology, kind of the interplay they have.
00:40:23.660It's like if you gave testosterone to a bunch of monks, they would start competing.
00:40:29.500Like, they wouldn't start beating each other up.
00:40:30.960They would start trying to out-compete each other who can meditate the most or who can do the niceness or something.
00:40:35.440But if you gave, like, testosterone to a prison gang, you'd probably see just a bunch of, you know, shanks and things like that.
00:40:43.440Yeah, that's what's fascinating is that it seems to promote whatever is necessary for a man or an animal, you know, in a given environment to gain status or to, you know, avoid, just to avoid being, to avoid losing status, say.
00:41:02.720So, it sort of increases your attention to those signals of status is how it seems to work.
00:41:09.720Your vigilance and your attention and your striving for status in whatever way is necessary.
00:41:15.520And in our deep history and still in many parts of the world, that was physical aggression.
00:41:20.760So, that's why males are larger than females and still are, you know.
00:41:25.160So, there's still those cues and women are still attracted to big, you know, tall, say, muscular, assertive men, even if there isn't any actual reproductive benefit.
00:41:40.540So, males are also still wired to, yeah, really care about status and be responsive to those cues in a way that women, you know, are responsive to different kinds of cues.
00:41:51.240And status just is not quite as important for female reproduction, of course, as it is for men.
00:41:56.860It still matters because females want to compete for the high-status males, and there aren't that many of them.
00:42:03.500Well, let's continue on this status strain here.
00:42:06.320So, I think it's interesting, you talk about studies that testosterone can, I mean, okay, influences this driver status chronically, systemically.
00:42:15.220So, it just kind of wires you for that.
00:42:16.520But there's these, like, 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.
00:42:31.100Like, what causes such a rapid change?
00:42:33.260Because, I mean, the production of testosterone takes a while.
00:42:35.100It has, like, the pituitary gland, it's a signal.
00:42:37.460So, like, what causes that super fast?
00:42:39.840Like, I mean, it's even, like, it's so weird, like, a guy can watch his favorite sports team lose, and, like, his T levels will drop immediately.
00:42:49.040So, I don't want to overstate the prevalence of this phenomenon.
00:42:53.600However, it does exist in humans and in non-human animals.
00:42:59.420And I think it'll be helpful just to say what happens in non-human animals.
00:43:02.700So, the Syrian hamster has been studied heavily regarding these testosterone changes, which I think are very important in humans.
00:43:11.640And, 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.
00:43:18.260Your sort of baseline level seems not to be super predictive of much.
00:43:23.400What 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.
00:43:32.860And this, to me, is absolutely fascinating.
00:43:35.960So, in Syrian hamsters, if a Syrian hamster has a fight with another male for territory.
00:43:43.440So, territory is the equivalent of any kind of resource in humans, because you need territory to get females.
00:43:48.260Because females will feed on the territory that a male can guard, basically.
00:43:53.780So, high-status males will have larger territories in the wild, anyway.
00:43:57.620And the outcome of, if you think about it from an evolutionary point of view, or even think about it from today.
00:44:03.200So, if you're fighting physically with another guy, if you lose, you need to know on some level that you're a loser.
00:44:11.340Like, 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.
00:44:21.260If somebody's in your face, you need to run away.
00:44:24.700Because you want to survive to try to win some other competition in the future so that you can mate, right?
00:44:30.140So, how do animals make those decisions about, how do they know, well, I need to, you know, fight or I need to flee, right?
00:44:39.620Those are decisions that animals have to make.
00:44:41.500So, when you're, when someone's threatening you, it may trigger in you the feeling that they're threatening you physically.
00:44:48.460Even 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?
00:45:02.760So, in the, in the hamsters, if a male loses a physical fight and he submits, right, he ends up by going on his back and getting on his back and submitting, his testosterone will tank.
00:45:16.520So, 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.
00:45:29.780And if you, and then the loser will fail to defend itself or defend its territory against a future threat, because he's lost, he's, that, that reduction in testosterone is somehow telling him he should be scared and run away.
00:45:45.580So, if you block that, 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?
00:45:58.460So, 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.
00:46:11.380So, if you're a winner, 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.
00:46:19.720If you have lost, you're fearful and anxious, and you retreat from confrontation.
00:46:24.980So, 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,
00:46:42.400and may help to account for different, even, you know, ways that people engage in competition in general, and just feeling like they are fearful or feeling like confident in the face of competition.
00:46:58.540So, yes, there's all kinds of examples in the human literature where, either from sports or, again, from competitions that are not physical, even.
00:47:10.800And then there's all these competitions that we don't measure, which are just males getting each other in each other's faces in some way, having subtle competitions, where there are these testosterone changes.
00:47:21.160It's tough to pin down experimentally, like, exactly when they happen and who they happen in and exactly what the function is.
00:47:28.060But 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.
00:47:47.780So, it increases motivation for the same behavior in the future, because it felt good last time.
00:47:53.740And 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.
00:48:07.000So, there's like a Matthew effect going on, right?
00:48:09.420He who has will be given more, who doesn't have will be taken away from.
00:48:14.360Yes, I think that's right, but it's adaptive for all.
00:48:17.780Basically, based on, but it's a way to, you know, 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.
00:48:32.940And I should just say, you raise a really interesting question, how does testosterone change in these situations?
00:48:39.120Because, like you said, the signal to produce testosterone in the testes comes from the brain.
00:48:45.800It 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.
00:48:59.120Then that testosterone would have to go through the blood and alter gene transcription, which, you know, theoretically should not have immediate effects on behavior.
00:49:08.100So, the answer is we don't know how social interactions can cause these testosterone rises.
00:49:15.120It may be that it's not coming from the testes, or it may be that it's not coming from LH, luteinizing hormone.
00:49:21.940It 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.
00:49:30.920But we don't know, and this is something that I've been obsessed with a long time, what is the mechanism here.
00:49:38.180Okay, so testosterone makes teenage boys, young adults, young adult males, preoccupied with sex, preoccupied with status.
00:49:46.240Well, I wouldn't say makes, but yes, heavily influenced.
00:50:15.700So, using – and what's interesting is if you think about the strategies over human evolutionary history that males and females would use to maximize their reproduction.
00:50:25.500And that's what natural and sexual selection acts on is, you know, the traits that animals possess that allow them to maximize reproduction.
00:50:35.220So, for females, taking physical risks is a bad idea because you need your physical integrity.
00:50:47.100That's what – because you don't have to worry about fighting for mates, right?
00:50:49.880You 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.
00:50:58.160So, it doesn't pay off for females to take physical risks, and they don't have that need to compete physically for mates.
00:51:07.020Although, they compete for mates, but in ways that don't put their physical selves at risk typically, right?
00:51:13.300So, males are relative to females over evolutionary history have benefited from physical aggression because they – that's what their bodies are, in a sense, built to do relative to females.
00:51:26.720That's where they're putting their reproductive energy budget.
00:51:29.760That's why they have bigger bodies and more muscle.
00:51:32.440That's the only reason relative to females.
00:51:35.480So, that muscle – that's a history of using their bodies to compete physically for mates.
00:51:40.920So, we retain that in a modern environment.
00:51:44.200And that's a – you know, again, that's attractive to females.
00:51:47.420It's not the case that they have to compete physically anymore.
00:51:52.040So, in different cultures, women are going to prefer men who have high status, whether it's gained physically or not.
00:51:59.600Like, 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 – you know, partly.
00:52:11.620But it's not – you know, he got that with his brain, not with his body, but it depends on the environment you're in and what pays off.
00:52:19.420So, we have this evolutionary history of physical aggression paying off, but it still plays out in the extremes.
00:52:27.100Yeah, I mean, you can see the propensity for physical aggression in males, just like crime reports.
00:52:31.820If you look at murders, physical assault, sexual assault, it's pretty much all dudes.
00:52:36.800You know, there's women there every now and then, but it's mostly dudes.
00:52:39.640But then if you look at crimes like fraud, shoplifting, et cetera, there's still more men, but, you know, women, that's more of where they kind of do their crime if they're going to commit crimes.
00:52:49.380Yeah, that's where the sex difference is reduced.
00:52:51.060So, women are going to commit crimes, but they're not going to – they're just much less likely to put themselves physically at risk to commit those crimes.
00:53:00.440Males are much more likely to put themselves physically at risk to commit crimes and to do everything else, like to show off, to, you know, thrill-seeking.
00:53:09.880Men are just far more likely to do that physically.
00:53:12.960Okay, so we've talked about testosterone's effect on behavior in males.
00:53:18.100Something that's been getting a lot of press lately is the role of testosterone in athletic performance.
00:53:23.200What do we know what's going on there?
00:53:26.800So, there's a lot of controversy and confusion around this area, but I'll just say that the science is clear.
00:53:35.780It's not confusing, and people who try to make it seem confusing, from my point of view, have a political or ideological agenda.
00:53:46.700It's totally clear that in the – almost all sports, there are some exceptions.
00:53:55.300Males, men – so if you're looking at the elite level, if you're looking at, you know, comparing highly trained people, you know,
00:54:01.340who are all taking care of themselves, all healthy, eating well, sleeping, training, you know, et cetera, men blow women out of the water.
00:58:02.260So, I mean, when people finish this book, like, what do you hope they walk away thinking?
00:58:06.580Yeah, I mean, there's a couple things.
00:58:08.460Of course, I'm incredibly interested in testosterone and the power of testosterone and how it shapes who we are.
00:58:15.620But 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
00:58:28.780and to not fear the truth and to do whatever we can to find and communicate the truth.
00:58:34.820That's what I see my job as a science educator.
00:58:37.020And that when you learn how things work, you have more power to make the world a better, safer, more equitable place.
00:58:47.280And so that is one thing I want people to come away with.
00:58:50.160I want them to see that it's possible to be clear and honest and open, but also sensitive and compassionate.
00:58:56.660And then the other point is, of course, about the hormone.
00:58:59.680There's just so much evidence that this one molecule shapes our society in these really profound ways
00:59:07.860and that the more we understand about how it works, the more we can capitalize on the positive aspects of being a man,