There Are People Born as Both Male and Female Who Are Not Hermaphrodites

Posted by Andrew on Oct 11, 2017 in Science

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Yes, you read that title correctly. I recently started watching a Stanford lecture series on behavioural biology with Robert Sapolsky. He is a fascinating scientist who promotes using knowledge from multiple biological fields to explain human behaviour. This is because there are accepted assumptions in every domain of science that are incompatible with those in others. So other than living with and studying other primate species like bonobos for many years, Sapolsky compares explanations from various fields. He uses these methods to figure out human behaviour. The areas of study include evolutionary biology, genetics, sociobiology, and epigenetics. I’m a huge fan of Sapolsky. Other than interdisciplinary study, and his discussion of the complexity of genetics and biology, he has long hair and a big scruffy beard. So he doesn’t fit the stereotype of scientists. He’s a genius who looks like a hippy, yet he’s never tried any drugs at all; not even alcohol.

When he explains genetics in one of his lectures, he describes a rare type of person whose existence I thought was impossible: Someone who is both female and male, but not a hermaphrodite. How the fuck does this ever happen? Great question.

Apparently, due to genetic mistakes and other factors, a small number of people are born with male genotypes and female phenotypes. This means that they’re genetically boys, but they look like girls. That isn’t too unusual, but it gets way more bizarre.

These people seem to be hybrids of the two different sexes in strange ways. They have vaginas, but with with no ovaries or uteruses. This means that they are technically boys who can have sex with boys as girls do, but they can’t get pregnant. These people also have internal, undescended testicles. So they have vaginas that you can see, but they also have testicles inside them.

In case that isn’t fascinating enough, it gets even stranger. Since these people have female phenotypes but male genotypes, they don’t menstruate during puberty. In fact, because they are genetically boys, their testicles still produce testosterone even though they are undescended.

However, the testosterone produced by their bodies has no physiological effects, which is why they keep looking like girls in spite of having testicles. Why doesn’t their testosterone change their phenotype? This is because they don’t make enough to cause this to occur. They would have to produce a certain amount in order for this to happen. Why don’t they make enough of it? The reason for this is that their testosterone is attached to an androgen receptor with a different shape than that of a normal one. If I understand correctly, the oversimplified definition of this receptor is that which produces testosterone. So since it has a different shape, it can’t produce as much as regular androgen receptors.

Is this mind-boggling enough for you yet? If not, then here’s some even more unusual information. Sapolsky also said that with these people, the phenotype sometimes changes after puberty! How is that even possible? Well apparently, in spite of the differently shaped androgen receptor, enough testosterone is produced during puberty with some of these people for a penis to be grown. Yeah, there are real people who look like girls and have vaginas until puberty, and then they grow penises and look like girls! This is so amazing!

How the fuck can that happen? Well, a lot of hormones are produced during puberty regardless of gender, right? So even though these people look like girls, they make male hormones since this is their genotype, which gets ramped up during puberty. Like I said, before puberty, due to the androgen receptor with a different shape, the testosterone that their testicles produce has no physiological effects because they don’t make enough. But for some of these people, the extra testosterone released during puberty causes them to grow penises in spite of the androgen receptors.

I’m always enthralled when I learn that something I thought was impossible is possible. It’s why I always try to remember one of my favourite sentiments of Socrates: I know nothing. There is always information that I am 99% sure is true. But there are also times when I discover that I am wrong about my most basic assumptions. I’m not a scientist, so I’m probably getting some of the details wrong about this small subset of our species. But guess what? There are real people who are born looking like girls but are actually boys. And if that isn’t unusual enough, these male/female hybrids sometimes appear to switch genders during puberty. They have been genetic boys but looked like girls for their entire lives, only to grow penises when they’re teenagers!

Bizarre facts of life like this are why I think that it’s important to remember that we can always be wrong. It also helps put our own likely mundane problems into perspective. Have you had a rough day at work? Did you open the fridge only to discover that your roommate ate the last piece of cake? There’s nothing wrong with righteous pity sometimes. But the next time something like that happens, try imaging what it’s like to be be born as a boy who looks like a girl, only to grow a penis as a teenager. Everyone has problems, but they can always be worse.

Originally published at on October 11, 2017.