Habits and Hustle
Episode 449: Dr. Sarah Hill: How Birth Control Changes Your Brain, Dating Choices, and Evolutionary Psychology
Tue, 13 May 2025
Is hormonal birth control affecting more than just pregnancy prevention? In this Habits and Hustle podcast episode, I am joined by Dr. Sarah Hill, an evolutionary psychologist and author who explains the surprising ways birth control pills influence women's brains, behavior, and mate selection. We discuss how synthetic hormones alter women's natural cycles, changing partner preferences and affecting emotional responses. We also explore the fascinating science behind mate selection through an evolutionary lens, why men are attracted to women at peak fertility, and how birth control can disrupt the pheromonal cues that influence attraction. Dr. Sarah Hill is an evolutionary psychologist, author, and researcher who earned her Ph.D. at the University of Texas at Austin working with Dr. David Buss. Her research focuses on understanding behavior and motivation through the lens of Darwin's theory of evolution by natural selection, with particular emphasis on women's psychology, hormones, and sexual motivation. What We Discuss: (00:00) Birth Control & Women's Psychological States (04:14) Effects of Birth Control on Emotions (15:26) Relationship Changes After Birth Control (19:22) Hormonal Birth Control and Pheromones (27:05) Partner Preferences and Attraction Triggers (34:43) Modern Dating Challenges and Hormones (39:01) Modern Dating Delays Marriage (42:51) Women's Relationship Choices and Evolution (48:07) Competition, Jealousy, and Marriage Threats (55:27) Divorce, Dating, and Female Friendship (01:04:43) Hormonal Birth Control and Side Effects …and more! Thank you to our sponsors: Therasage: Head over to therasage.com and use code Be Bold for 15% off TruNiagen: Head over to truniagen.com and use code HUSTLE20 to get $20 off any purchase over $100. Magic Mind: Head over to www.magicmind.com/jen and use code Jen at checkout. Air Doctor: Go to airdoctorpro.com and use promo code HUSTLE for up to $300 off and a 3-year warranty on air purifiers. Bio.me: Link to daily prebiotic fiber here, code Jennifer20 for 20% off. Momentous: Shop this link and use code Jen for 20% off DavidProtein: Try David today—buy 4, get the 5th free at davidprotein.com/habitsandhustle. Find more from Jen: Website: https://www.jennifercohen.com/ Instagram: @therealjencohen Books: https://www.jennifercohen.com/books Speaking: https://www.jennifercohen.com/speaking-engagement Find more from Dr. Sarah Hill: Website: https://www.sarahehill.com/ Books: https://www.sarahehill.com/your-brain-on-birth-control/ Instagram: https://www.instagram.com/sarahehillphd/
Chapter 1: How does birth control change women's brains and behavior?
We dive into how the pill can alter sexual desire, stress response, emotional sensitivity, and even influence the type of partner you're drawn to. It may even affect your mental health and motivation in ways most women aren't told. So whether you're using birth control or just curious, this is an eye-opening conversation that will change how you think about hormones and your identity.
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We have Dr. Sarah Hill on the podcast today, who is an evolutionary psychologist. By the way, I want you to tell us what that is. But she is someone who talks all about hormones, the effects of birth control. You wrote a whole book on this. And mating, which is, again, I love all your stuff. So I'm so happy you're here today.
Thank you. I'm so excited to be here. And I will tell you what an evolutionary psychologist is.
Please.
So I'm a psychologist. And the thing I'm really interested in is trying to study behavior and motivation. So I'm really interested in why people do things that they do. And the lens that I use to do my research is that of Darwin's theory of evolution by natural selection.
And all that that means is that I use the tools from evolutionary theory to make new predictions about why people do the things that they do and think the things that they think and feel the things that they feel.
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Chapter 2: What are the effects of hormonal birth control on partner selection?
Yeah, absolutely. So the first thing that we need to do is just orient ourselves to a naturally cycling woman. So this is somebody who's not using hormonal birth control. And let's learn a little bit or talk a little bit about what their hormones do.
And so if you are a naturally cycling woman, meaning you're not on the pill but you're having cycles, the first day of your cycle is the day you get your period. So that's why your doctor's always asking, when was the first day of your last menstrual period? It's because that is the start of your cycle. And at that point, your levels of sex hormones are really low.
So even though women get a hard time all the time about, you know, being hormonal because they're having that period, that is like literally the time in the cycle when our hormones are at their absolute lowest. And when our hormones are really low, that tells our brain that it needs to stimulate our ovaries to begin egg follicle maturation.
So our brain tells our ovaries, start working on some eggs. And as those eggs are beginning to develop, that leads to the release of estrogen. And as the eggs are maturing and developing and getting ready to ovulate, estrogen levels rise, rise, rise, rise, rise.
And so for naturally cycling women during the first two weeks of the cycle, it's characterized by this nice, beautiful rise in estrogen that corresponds to the period of time in the cycle when sex can lead to conception.
And so it's not surprising that what we tend to see with research in estrogen is that when estrogen is high and rising, like getting close to ovulation, women experience increases in sexual desire. They feel sexier. They have more sex. They're more likely to have orgasms. They have more energy. They're more attuned to all things related to mating. So they notice men.
They can decipher the scent differences between different types of men. They're cued into testosterone levels in men. And All of these things correspond to this big rise in estrogen that women get right prior to ovulation because this is the time in the cycle when sex can lead to conception, right?
And so it's like evolution by natural selection made our brain primed for mating and the ability to sort of distinguish between high and low quality mates at this time when estrogen is high and rising. So then you ovulate, and then that empty egg follicle actually becomes a temporary endocrine structure, and it starts to release a second sex hormone called progesterone.
So the first two weeks are characterized by this high and rising levels of estrogen that corresponds to the release of the egg, women feeling gloomy. and happy and sexy and flirty and noticing men, and then all of a sudden their estrogen levels crash, and instead it's replaced by the second sex hormone, progesterone, which remains relatively elevated for the last two weeks of the cycle.
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Chapter 3: How do natural cycles influence women's attraction and mate choice?
Like what?
So for example, like a man's provisioning ability. So is he going to be a stable financially providing partner? Is this somebody who's going to be somebody that they see as potentially a good father? And obviously these are incredibly important things, right? Most women who are choosing long-term mates wouldn't look at that list of characteristics and say, this is a terrible decision, right?
It's terrible, but it's going to lead you to something a little bit different, right? And sometimes- Well, yeah.
More secure.
Yeah, more stable, more secure. Yeah, more feminine. And what's really interesting about this is that when the researchers have done studies where they looked at the divorce rate of women who chose their partners when they're on or off the pill, and women who choose their partners when they're on the pill are less likely to get divorced.
But when they do get divorced, they're overwhelmingly the ones who initiate it, which is also really interesting. Right. Really?
Yeah.
And so it suggests that it does lead to more relationship stability in some ways, because you're sort of choosing based on your head, you know, not your heart, but that of course comes at a cost. And for some women, what happens when they go off of hormonal birth control is
and they do start cycling again, and all of a sudden they're going through these periods of estrogen surge, if all of a sudden they don't like what they see or what they smell in some cases, then it leads them to become less sexually attracted to their partner, and sometimes it can lead to relationship breakups.
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Chapter 4: Do men prefer women who are naturally cycling?
It's like everything is shut off.
It's just blunted. Yeah, it's just blunted. It's that blindfold from like we've been talking about from that show, Love is Blind.
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Trust me, you'll be happy you did. So then women, though, who are not on birth control, they typically, like, what is attractive to a woman naturally? And what is attractive to a man naturally?
Okay. Yeah. And obviously, when I answer this question, it's going to have huge error bars around it because there's so much idiosyncrasy in everybody's partner choice.
Yes, of course.
But just, you know, like there are some things that men and women tend to desire sort of in equal measures. And so like men and women both want a partner who's, you know, kind and understanding and a partner who's in good health. And these are things that men and women are both looking for in ways that men and women on average tend to differ in terms of their partner choice.
Women, a naturally cycling woman likes to strike a balance between what in the evolutionary sciences we would call direct and indirect benefits. Direct benefits are all of those things that you get yourself from your partner. So for example, if they are a good provider, that would be a good direct benefit. And that's one that we know that women desire in their partners.
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Chapter 5: What are the differences between hormonal and non-hormonal IUDs?
Broad shoulders, deep voice, you know, a dominant sort of personality. These are cues related to testosterone and testosterone is what we call a good genes marker. Simply because men who were able to release high levels of testosterone during development, that indicates that they probably had a high quality immune system because men's immune systems get traded off with testosterone in a way.
that men's bodies will not produce high levels of testosterone if they have an immune emergency to deal with. And so the idea here is that only men who are in good health during development are able to release really high levels of testosterone during development because there is this trade-off between immune system functioning and testosterone levels.
And so one of the reasons that our brain finds testosterone related cues sexy in men is because only men who had relatively high functioning immune systems during development were able to release that and form those types of features. And so, yeah, so that's like one type of a cue. The scent of genetic compatibility, that's another set of sort of genes that we're looking for.
And we tend to pick this up by way of scent, right? Sort of picking up on some of those cues that somebody might have different immune genes than your own. which are generally the ones that we find most attractive. And for most naturally cycling women, what you see is that when we're choosing a partner, it's generally brokering that trade off.
You know, it's like sort of understanding you want the sexy qualities that are going to, you know, just like really attract you and make you physically drawn to somebody. But then also as a long term partner, somebody who's going to be, you know, sort of a good provider and, you know, be a good parent and so on and so forth.
And, you know, so for naturally cycling women, what you generally see is that there is some sort of trade-off, right, where they're making decisions about, you know, this person has to be somebody I'm attracted to, but also has to have these other qualities. And then you find the person who best, you know, matches that set of criteria.
For women who are using the pill, it seems like all that, you know, what we call indirect benefits, that genetic compatibility and cues of, you know, immune system quality because of testosterone and all that, it seems like all that just gets shut down. It's just like the light switch goes off.
And it's just, it's focusing exclusively on these other partnership qualities, which again, isn't necessarily bad, right? It's just different.
It's going to get you a different partner probably than what you would get if you were striking that balance between what, you know, who you're most physically attracted to and then, you know, who's going to be a good partner and, you know, good at provisioning. And so that's, you know, men tend to be, you know, in a sort of natural state of things.
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Chapter 6: Why might there be a mating crisis in modern society?
Yeah, well, exactly. And so it's like, you know, I'd have, I didn't, um, at first I was, I was hurt and angry. And then afterwards I was, I had a little bit of reflection on it and it's like, you know, I under, I mean, there's two things going on there. It's like one, you know, you don't want to have this single person that that's a threat.
Um, but it's also a threat to, I mean, marriage is kind of held together by bubble gum and shoelaces. You know what I mean? It's like, it's like a, it's like a It's a hard thing to do, you know? It's, like, really hard to do. And so the idea that somebody can just, like, walk away from it and be okay. Because I was. I, like, walked away.
And, you know, and my ex-husband and I, in some ways, it's even more threatening. He and I are great. And, like, we're great co-parents. And we do Thanksgivings together. And, you know, we call it the web of love. How long were you married for? Like, 17 years. So I was married a long time.
And how old were the kids when you got the divorce?
I want to say 12 and nine. Wow. Yeah. So yeah. And yeah. So, so, so to have somebody who we, you know, I walk away from a marriage and I'm okay. And financially I'm fine. Cause I've, you know, I'm taking care of my business and then to be able to get along well with my ex-husband. And I feel like that also feels threatening to marriage. Do you know
Really? Why?
Because marriage is hard and horrible sometimes. And being somebody who's married again, it's like, and we talk about this. My husband was also formerly married. And it's like really hard to be married. I mean, it's like sometimes you're just like, this is terrible. Like, this is a really terrible thing. But you persevere. And the idea of like...
When you're having one of those moments of marriage being terrible, to see people walking away from it and being just fine, that feels really threatening. You don't want to go down that rabbit hole. Nobody wants to have to sit and think about whether their marriage is a good idea or a bad idea. It's a really scary thing. It was a hard decision.
I think also it makes people think to themselves, they're jealous a little bit. I wish I could do that. Why can't I do that? Will I be okay? Or they feel trapped because financially they're trapped. There's all these other them issues that you're basically forcing them to look at.
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