Andrew Huberman

The larger the number of older brothers that a male has, the higher the probability that he is gay.

Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life.

I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine.

My guest today is Dr. Mark Breedlove.

Dr. Mark Breedlove is a professor of neuroscience at Michigan State University, and he is an expert in how hormones shape the developing brain, in particular, how they influence sexual orientation.

As you'll learn today, the amount of testosterone that a fetus is exposed to while in the mother has a profound impact, not only on the ratio of finger lengths, yes, you heard that right, but it also plays a meaningful role in sexual orientation.

And in fact, there's a correlation there between finger length ratios and sexual orientation.

Now, as wild as that may seem, that result has now been confirmed many times over in humans and in animals.

And today you'll understand why.

You'll also learn that every time a woman is pregnant with a male, there's a biological trace of that, which biases the likelihood that her next male offspring will be either heterosexual or homosexual.

Now, I know this sounds really out there, but these are extremely solid biological findings for which the mechanisms are now understood for both animals and humans.

It turns out that the hormones we are exposed to while we are in the womb shape not only the preference for whether somebody is attracted to males or females, but also an aversion to the opposite.

meaning there appears to be the formation of circuits for being attracted to one sex and not attracted to the other.

Today, you'll also learn how hormones impact the amount of rough and tumble or social play that kids engage in the interplay between nature and nurture in shaping male versus female differences and sexual orientation.

Dr. Breedlove is one of the longstanding pioneers in this field of how hormones shape brain development and psychology.

We approach these questions through the lens of biology and statistics.

So today's is not a political discussion.

Instead, it's a discussion about what is known and what is still not known about this profound aspect of our species.

Oh, and we also talk about gay Rams.

Yes, that's a real thing.