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Is testosterone really the fizzy tonic of manhood that we imagine?

Maybe not, suggest a recent batch of books with titles like “Testosterone: An Unauthorized Biography.”

The “male sex hormone,” as they are quick to point out, is present in women, too. And there’s not much evidence that guys with a big supply can pump more iron or run any faster than their “low-T” compadres.

So much for the late-night-TV charlatans selling “vigor and vitality” in a bottle.

But the implications of the T skeptics’ argument run much deeper than that. If testosterone isn’t as potent as believed, then biological explanations for differences in male and female behavior would lose a lot of their power. And culture and expectations would emerge as the primary drivers of traditional gender roles.

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For anyone hoping to topple the patriarchy, that would be cause for hope — culture, after all, is mutable.

But alluring as that idea may be, Carole Hooven, a lecturer in the Department of Human Evolutionary Biology at Harvard and author of the new book “T: The Story of Testosterone, the Hormone That Dominates and Divides Us,” isn’t having it.

Early in her scientific career, she witnessed what looked like the raw, unmediated power of testosterone up close, tracking chimpanzees in the Kibale Forest of western Uganda. At one point, she watched an alpha male named Imoso savagely beat a female named Outamba with a stick — making her the first researcher to witness a nonhuman primate using a weapon in that way in the wild.

Her review of the literature on humans has only solidified her views. Sure, testosterone levels (when they are in the normal range) aren’t related to athletic performance within sex. But it’s clear, she argues, that T explains sporting differences between men and women.

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Obscuring that biological divide serves no one, she says. If we want to improve relations between men and women, then we must acknowledge — and face up to — the difference in our natures.

I spoke with Hooven via Zoom about her book, the fallout from the #MeToo movement, and how her research has changed the way she views her husband. The interview has been edited and condensed and includes some clarifying thoughts she added later by email.

In your book, you say socialization plays an important role in shaping gender. But you also make a pretty strong case that “T makes boy brains.” So give us that case, in brief.

It’s a little bit tongue in cheek, the “T makes boy brains.” But I’m trying to make a point: There’s clear evidence that higher testosterone levels in the womb do masculinize behavior, on average, and that is independent of human culture.

Take rats. In order to mate, the male has to do one thing and the female has to do another thing; they have to engage in certain poses and execute certain movements. And for the male to be able to pursue and mount the female, his fetal brain must have been exposed to high levels of testosterone.

And it’s not just sex, it’s also aggression. Adult males fight each other for mates and practice these behaviors through play fighting when they’re young. They engage in rough-and-tumble play at much higher rates than females, and the expression of the behavior is dependent on male-typical levels of T in utero.

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The human evidence is more indirect because we can’t do these experiments. However, we can look at situations in which testosterone exposure in utero departs from the typical pattern.

There is a condition called congenital adrenal hyperplasia. Fetuses are exposed to unusually high levels of testosterone. It doesn’t seem to make much of a difference in boys, because they already have very high levels of testosterone and having more than that doesn’t seem to have an effect.

But female fetuses are extremely sensitive to elevations in T levels. You will get masculinization, to varying degrees, of the genitalia. And these girls are masculinized in their childhood behavior. They have higher rates of rough-and-tumble play. They tend to prefer male-typical toys like trucks and guns and things with moving parts. In adulthood, they are more likely to be lesbians. They have an increased preference for male-typical professions.

This doesn’t mean that culture doesn’t matter and can’t shape our behavior. But I would argue that we are born, on average, with somewhat different natures, because evolution has shaped different reproductive strategies in each sex.

That to me is the simplest way to explain the sex differences in human behavior that we observe. I just don’t see the logic in the argument that humans — even with our complex culture — have somehow escaped the evolutionary and genetic forces that shape the behavior of every other animal.

What is the harm in skepticism about the importance of T?

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I think that skepticism is healthy. I am a huge skeptic as a scientist. However, the skepticism that is brought to questions about the biological underpinnings of sex differences is unreasonably high.

There are problems with some of the studies, just as in any scientific literature. But what we need to do is look at the body of evidence as a whole and really see where it points.

The excessive skepticism about T is usually accompanied by a push to reject biological explanations for sex differences in favor of cultural ones. The thinking seems to be that if culture is the cause of male dominance and toxic masculinity, and biologically we’re all the same at birth, then we can solve our problems by changing culture. If we’re all the same from birth and culture makes us different, then we can hold out hope for sex equality and a safer, more peaceful world.

This kind of thinking is problematic because first of all, it’s not true. Second, we can work towards those goals of greater equality and safety even if we are different. And third, the distortion of good science confuses people and robs us all of the tools we need to understand the world we live in and the people around us.

I sense some shame about men’s sexual impulses in the #MeToo era. Is that a healthy corrective to some pretty awful behavior or is the shame misguided in some way?

I think behavior and consequences are what we need to be focused on. So, men taking advantage of women? Yes, shameful, horrible, needs to be addressed immediately.

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However, men feeling a struggle about wanting to do certain things? No, we can’t shame people’s natures.

Born biologically female, Braiden Schirtzinger now identifies as nonbinary. They have a tattoo that marks the spot of their first testosterone injection at age 24.
Born biologically female, Braiden Schirtzinger now identifies as nonbinary. They have a tattoo that marks the spot of their first testosterone injection at age 24.Toni L. Sandys/The Washington Post

I wonder if your research into testosterone has changed the way you view the men in your life.

I’ve been thinking about testosterone for so long, but it wasn’t until I wrote the book that I changed the way that I interact with my husband. And it’s sort of embarrassing when you realize that you might have been wrong about something so important.

I am very emotionally expressive, it comes very easily to me — a little too easily, and I find that a little bit difficult. And I don’t think it’s a coincidence that I paired up with someone who is — he’s a philosopher, he’s British, he’s very steady and stable. He’s very loving, but in terms of emotional expression — and even what seems to be going on inside of him emotionally — he will say to me, “Well, really, not much is happening. I’m thinking about xyz philosophy thing.” So for a long time, I was wondering, “What is wrong with you? Where’s your rich inner emotional life? You never talk about your feelings.” Kind of pushing him and nudging him, which really caused him to close up a little, because I think he felt judged and misunderstood.

And for whatever reason, writing the book — it doesn’t mean that who he is is caused by having higher testosterone. We don’t know that about any individual. But just having this explanation, doing this research, especially with transgender people — reading the scientific literature and talking to them about how their emotional lives changed on and off testosterone, that blew my mind. A female-to-male person who goes from hardly any testosterone to male-typical levels — the literature and the people I talked to said they basically stopped crying. And they had less access to their emotions or they had a reduced range of emotion.

This just sort of sealed the deal. I just felt like, “Oh my God, this is just who my husband is. We’re different. We’re just different.” And it did help me to stop prying and pushing and do more accepting. And I think it changed our dynamic and he felt more comfortable to just be who he is.



David Scharfenberg can be reached at david.scharfenberg@globe.com. Follow him on Twitter @dscharfGlobe.