Carole Hooven is a human evolutionary biologist whose research centers on testosterone, sex differences, and behavior. In this episode, she explores how prenatal testosterone orchestrates male development in the body and brain, how early hormonal surges shape lifelong behavioral tendencies, and what rare natural experiments—such as 5-alpha-reductase deficiency—reveal about the biology of sex differentiation. She discusses distinct male and female aggression styles through an evolutionary lens, how modern environments interact with ancient competitive drives, and the implications of attempting to suppress them. The conversation also covers testosterone across the lifespan, the role of hormone therapy in both men and women, and Carole’s own experience after surgical menopause, culminating in a broader discussion of masculinity, cultural narratives, and the consequences of denying biological sex differences.
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We discuss:
Timestamps: There are two sets of timestamps associated with the topic list below. The first is audio (A), and the second is video (V). If you are listening to this podcast with the audio player on this page or in your favorite podcast player, please refer to the audio timestamps. If you are watching the video version on this page or YouTube, please refer to the video timestamps.
- How Carole became interested in exploring the biological and evolutionary roots of sex differences and the role of testosterone [A: 2:30, V: 0:11];
- How testosterone and other hormones influence sex differences in aggression and behavior across species [A: 9:45, V: 8:25];
- How chromosomes, the SRY gene, and early hormones direct embryonic sexual differentiation [A: 12:15, V: 11:09];
- A stark contrast of male social bonding compared to females, and evolutionary parallels in chimpanzees [A: 19:30, V: 20:04];
- How hormones like DHT shape sexual differentiation, and how 5⍺-reductase deficiency reveals the distinct roles of these hormones [A: 22:45, V: 23:43];
- How sex chromosomes and prenatal testosterone shape early brain development and explain sex differences in childhood behavior [A: 31:30, V: 34:20];
- How gamete differences shape reproductive strategies, energetic costs, and sex-specific behavior [A: 42:30, V: 47:13];
- How evolutionary biology shapes sex differences in play, aggression, and conflict resolution (and how modern environments and cultural messaging can disrupt those patterns) [A: 49:00, 55:04];
- Why males commit disproportionately more violent crime, and how cultural and environmental forces shape aggression [A: 1:01:00, V: 1:09:10];
- Why females evolved different behavioral strategies: nurturing, risk aversion, and the cultural norms that override biology [A: 1:04:00, V: 1:13:12];
- Whether male aggression is still necessary in modern society, why the underlying biological drives persist, and how modern society redirects these drives [A: 1:06:30, V: 1:15:59];
- How testosterone levels naturally shift to support fatherhood and caregiving [A: 1:13:30, V: 1:24:45];
- How testosterone shapes male mating strategies, and why long-term pair-bonding persists even when reproduction is no longer at stake [A: 1:18:30, V: 1:30:38];
- The distinct roles of estrogen in male development, mood, libido, and muscle [A: 1:25:00, V: 1:38:42];
- How evolution, health, lifestyle, and androgen receptor biology shape modern testosterone replacement therapy (TRT) [A: 1:34:15, V: 1:49:50];
- Carole’s experience with hormone replacement therapy (HRT), and the risks associated with TRT in younger men [A: 1:45:15, V: 2:02:44];
- How Carole rebuilt after controversy: leaving academia and recommitting to scientific honesty [A: 1:51:30, V: 2:10:32];
- Carole’s next book: examining masculinity, cultural narratives, and the cost of denying biological sex differences [A: 1:57:30, V: 2:17:40]; and
- More.
Show Notes
How Carole became interested in exploring the biological and evolutionary roots of sex differences and the role of testosterone [A: 2:30, V: 0:11]
- Sex hormones are a topic that we talk a lot about on the podcast, but usually from a pretty narrow lens, which is in the form of replacement (both in men and women)
- We talk about how they wax and wane as an individual ages
- We talk about the medical use of them
- But we haven’t spent any time understanding the more basic fundamentals of these hormones
- The role they play in our evolution
Anecdotally, Peter shares an observation that any parent probably has, if they have male and female children
- His first child was a girl, and his wife and he very stupidly and arrogantly thought they were the perfect parents, because she was so well-behaved
- They were like, “What do all of these other parents with their boys running around misbehaving… What are they doing wrong? How could we teach them how to be as good as we are?”
- They didn’t actually say that, but there was undoubtedly an annoying smugness to them
- And if you believe in a God, that God smacked them into their place with 2 boys that followed who were, for all intents and purposes, treated the same way, socialized the same way
- And there is a level of aggression in them, a fury in them that Peter has never seen, probably unless he were to go back and hear stories of what his mom said he was like
- His boys are now 8 and almost 11
Peter adds, “I wouldn’t say they’re a different sex. I would say they’re a different species.”
- Peter doesn’t feel that they did anything different [parenting the boys]
- And yet, they couldn’t be more different
- He appreciates that that’s not going to be the case for every parent
What Peter hopes to learn is how much testosterone has to do with that
- Because he is also under the impression that at this age, the testosterone levels wouldn’t be that much different
- We’ll probably talk about the differences in testosterone levels during the embryologic phase, because obviously that led to the differences
- That is a backdrop to this conversation
How did you get interested in this topic?
- Carole grew up with 3 older brothers, and they were different than she was in some consistent ways
- Though she didn’t think much about it at the time
That probably made her want to understand what motivates male behavior in general and why it’s different from female behavior
- Studying this wasn’t an idea she had when she was in college
- But she did become intensely interested in the evolutionary origins of human behavior in general and what makes us different from other animals
- And that was because of traveling
- She traveled by herself to a lot of different places in the world, during and after college
- There were extreme differences culturally ‒ Egypt was a place that really freaked her out
- The cultural differences were so profound in terms of the incredibly important role that sex plays in social life and the segregation and different rules that applied to males and females
- Carole was alone, traveling by herself as a young woman, totally ignorant of what she was getting into in Egypt
- She was harassed endlessly
- Some of that was her fault for not understanding the culture well enough and what she was getting into
- This combination of being immersed in, not only different societies that treated sex and sex roles very differently, but also different ecologies
- She spent some time in Africa and Kenya and Tanzania and got really interested in all of the animal behavior and why we are different from other animals
- She had a whole other career before graduate school, and she ended up leaving that career and applying to Harvard to try to do a graduate degree where she could do more to understand the evolutionary basis of human behavior
- She ended up getting rejected
She just persisted and then was offered this job out in Uganda studying chimps for what was supposed to be a year ‒ that is what really triggered her interest in sex differences and testosterone
- Because to a certain extent, we are indoctrinated to believe that most human sex differences are cultural
- Or if you think that they’re not, it’s better you don’t say that out loud to too many people or in the wrong place
When she spent time with the chimps, she was really blown away by the ways that the sex differences in the chimps paralleled human sex differences
- Of course, not exactly the same, but the very basic things that Peter just described in terms of energy and aggression, are present in the chimps in terms of being higher in the males and lower in the females
- The reasons for that are so profound and far-reaching and start with sperm and egg
- That’s what sex really is about
- Not just the ability to produce sperm or eggs
- But the way that the organism is designed and the reproductive phenotype including body and behavior
- [explored more in this essay Carole recommends]
- That, in humans, plays out in these really complex ways in terms of social systems
- Carole got interested in testosterone because this is one thing she could grab onto that links very clearly humans, chimpanzees, every other mammal in terms of males having much higher levels than females
- And it’s not just mammals; there are other forms of steroid hormones that other species have
- But this is pervasive and just a very powerful way to understand proximately that means what’s happening here and now in the organism, why the sexes are different
There are these deep evolutionary pressures that have to do with reproductive strategies for organisms that produce sperm versus organisms that produce eggs
- She ended up reapplying to Harvard and getting into the grad program there
Carole did her dissertation on testosterone and sex differences in cognition, the way we think and process information
- She had men watch sexy videos and also videos of dental surgery and collected their saliva and measured their testosterone in the lab
- Then she stayed on at Harvard, mostly just teaching
How testosterone and other hormones influence sex differences in aggression and behavior across species [A: 9:45, V: 8:25]
- Peter wants to go back to the distinction between mammals and non-mammals
- He never really thought of it until she mentioned this
- Differences if he were to look at a male great white shark and a female great white shark
Do great white sharks have testosterone in them as the androgen or sex hormone?
{end of show notes preview}
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Carole Hooven, Ph.D.
Carole Hooven earned a B.A. in Psychology from Antioch College and a Ph.D. in Biological Anthropology (which later became the department of Human Evolutionary Biology) from Harvard University. Until recently, Dr. Hooven taught in and co-directed the undergraduate program in the department of Human Evolutionary Biology. She explains her decision to leave Harvard in an article published in the Archives of Sexual Behavior and on her website. She is now an Associate in the Department of Psychology at Harvard University in Steven Pinker’s Lab and an active member of the newly established Council on Academic Freedom at Harvard. Dr. Hooven also works as a nonresident senior fellow at the American Enterprise Institute where she focuses on issues related to sex and gender, human evolutionary biology, health, psychology, and academic freedom in higher education.
Dr. Hooven is an evolutionary biologist whose research focuses on behavioral neuroendocrinology—the relationship among hormones, the brain, and behavior in humans and other animals. She is particularly interested in how evolutionary forces and hormones shape the intricate interplay between human biology and culture, helping explain large patterns of behavior, such as in crime, education, and mating strategies. She is also a public advocate for free speech and evidence-based social, educational, and legal policies concerning sex and gender. Dr. Hooven is the author of the influential and widely praised book T: The Story of Testosterone, the Hormone That Dominates and Divides Us. [AEI]
Instagram: @carole.hooven
TED talk: How Testosterone and Culture Shape Behavior
Website: Carole Hooven
X: @hoovlet
