Huberman Lab How Hormones Shape Sexual Orientation & Behavior | Dr. Marc Breedlove
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Mar 30, 2026 
Marc Breedlove, a Michigan State neuroscientist who studies hormones and brain development, explores how prenatal testosterone may influence later attraction. He gets into finger-length ratios, why older brothers can slightly shift the odds, and what cases like CAH and AIS reveal. There’s also a look at gay rams, brain differences, and how nature and nurture interact.
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Orientation May Depend On Attraction And Aversion
- Huberman and Breedlove suggest sexual partner choice may involve both attraction circuits and aversion circuits, not attraction alone.
- Breedlove notes some men find same-sex contact aversive while many women appear more sexually plastic, and gay rams may show female-directed aversion.
Intersex Conditions Clarify Hormone Effects
- Congenital adrenal hyperplasia in XX individuals raises prenatal androgen exposure and increases later same-sex attraction on average, though most remain straight.
- Androgen insensitivity syndrome creates XY people with female bodies who usually grow up as straight women, leaving biology-versus-socialization unresolved.
Older Biological Brothers Shift Odds Upward
- One of the strongest findings in human sexuality is that each older biological brother raises a male’s odds of being gay by about one third.
- The effect disappears for stepbrothers but holds for biological brothers raised apart, pointing away from social explanations.
