How Hormones Shape Sexual Orientation & Behavior | Dr. Marc Breedlove

Huberman Lab

Scicomm Media

Science, Life Sciences, Health & Fitness

4.8 • 30.3K Ratings

🗓️ 30 March 2026

⏱️ 131 minutes

🔗️ Recording | iTunes | RSS

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Summary

Dr. Marc Breedlove, PhD, is a professor of neuroscience at Michigan State University and an expert on how hormones shape brain development and sexual orientation. We discuss how prenatal testosterone impacts whether someone is romantically attracted to men or women later in life, and what correlates of sexual orientation — such as finger-length ratios — tell us about the role of hormones in brain and psychological development. We also discuss why the number of older brothers a male has biases sexual orientation. Throughout, we explain how nature and nurture interact to shape male-female differences, behavior, and romantic partner choice. Thank you to our sponsors AG1: https://drinkag1.com/huberman David: https://davidprotein.com/huberman Rorra: https://rorra.com/huberman Function: https://functionhealth.com/huberman Timestamps (00:00:00) Marc Breedlove (00:03:24) Hormones & Sexual Orientation (00:07:37) Prenatal Testosterone, Finger Ratio, Men & Women Differences (00:14:08) Sponsors: David & Rorra (00:16:46) Finger Ratios, Prenatal Testosterone, Gay & Straight Men/Women (00:23:57) Mice & Sex Differences, Androgens (00:26:54) Brain Differences & Sexual Orientation (00:33:52) Group vs Individual Differences, Height Analogy; Bisexuality (00:36:57) Brain Development, Hormones & Behavior; Brain Plasticity (00:42:52) Sponsor: AG1 (00:44:16) Sexual Behavior, Libido (00:51:37) Gay Rams, Brain Differences (00:58:00) Aversion Pathway, Men vs Women, Same-Sex Partner (01:06:58) Congenital Adrenal Hyperplasia (CAH), Intersex Phenotypes (01:13:55) Androgen Insensitivity Syndrome (AIS) (01:18:14) Sponsor: Function (01:19:25) Gay Men & Older Brothers, Maternal Immunization Hypothesis (01:32:55) CAH Carriers, Advantage, Stress Tolerance (01:35:41) Birds & Sexual Differentiation, Gynandromorphs (01:41:32) Anabolic Steroids, Hypersexuality; Adult Brain Plasticity (01:45:31) Age & Testosterone Decline; Sexual Orientation & Activities (01:53:14) Marc's Academic Journey, Ozarks, Luck (02:02:35) Exploration; Kids & Sex Differences (02:08:47) Zero-Cost Support, YouTube, Spotify & Apple Follow, Reviews & Feedback, Sponsors, Protocols Book, Social Media, Neural Network Newsletter Disclaimer & Disclosures Learn more about your ad choices. Visit megaphone.fm/adchoices

Transcript

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0:00.0	The larger the number of older brothers that a male has, the higher the probability that he is gay.
0:07.3	It's been seen over and over. I mean, it's really one of the rock-solid findings in human sexuality.
0:14.2	So the way to emphasize the difference is if a baby boy is born today, if he has no older brothers, his odds of being gay when he grows up is about 2%, right?
0:26.9	Pretty low.
0:28.2	But if he had one older brother, his odds go up by a third.
0:33.1	Okay, 2.6.
0:34.8	And if he has two older brothers, they go up a third again.
0:38.2	All right. Now we're at 3.5. It turns out you've got to have like a dozen older brothers just to have a 50-50 chance.
0:43.2	Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life.
0:52.2	I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School
0:57.6	of Medicine.
0:58.7	My guest today is Dr. Mark Breedlove.
1:01.2	Dr. Mark Breedlove is a professor of neuroscience at Michigan State University and he is an
1:06.0	expert in how hormones shape the developing brain, in particular how they influence sexual orientation.
1:12.6	As you'll learn today, the amount of testosterone
1:14.8	that a fetus is exposed to while in the mother
1:17.3	has a profound impact not only on the ratio of finger lengths,
1:21.4	yes, you heard that right,
1:22.9	but it also plays a meaningful role in sexual orientation.
1:26.4	And in fact, there's a correlation there
1:28.4	between finger length ratios and sexual orientation.
1:32.2	Now, as wild as that may seem,
	...

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