Why Some Babies with Male Genes Have Female Parts

To their own surprise and that of their parents, some babies born with male genes end up with female parts.

By Jared Diamond
Jun 1, 1992 12:00 AMMay 3, 2023 5:23 PM
Woman carrying her baby girl at home
(Credit:StockPlanets/Shutterstock)

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Barbara grew up as an apparently normal girl enjoying a happy childhood. As her teenage years approached, she looked forward to experiencing the same sexual development she saw in older girls. Gradually, however, she began to have a vague sense that the expected changes weren’t happening in her. By the age of 14 she was really worried: She had not yet menstruated and her breasts showed no signs of growth. What she did have was a pain in her left groin that eventually subsided, only to be replaced by the appearance of a mass in the left side of her labia. With growing shock, she felt her voice dropping, her facial hair growing, and her clitoris enlarging to become more and more like a penis.

After Barbara’s sixteenth birthday, her penis developed erections, she produced ejaculations, and she found herself feeling a sexual interest in girls. By now she had become convinced that she was really a boy and that the mysteriously shifting mass within her was in actuality a testis. But Barbara still struggled with the problem of how to present herself to her parents and friends, before whom she avoided being caught naked. She knew they had to suspect something. When they found out, would they ridicule her — or him — as a freak?

Gender constitutes the most fundamental distinction we make among ourselves, the first question we ask when a baby is born. It establishes two radically contrasting possibilities and determines how we view ourselves and how other people view us. In almost all cultures it also establishes a division between contrasting economic and social roles. To find one’s gender ambiguous or shifting is as cruel a blow as could befall one’s ego. It’s as close as any of our children might come to the nightmare experienced by Gregor Samsa, of Franz Kafka’s terrifying story Metamorphosis, who wakes up one morning to find himself transformed into a human-size insect.

The vast majority of us are born unmistakably male or female and remain that way throughout life. We have all the sexual parts appropriate to a single gender, with no discordant pieces. It is very rare indeed that you find among humans true hermaphrodites — individuals possessing both male and female gonads.

However, there are some unfortunate individuals called pseudohermaphrodites, whose sex presents an ambiguous appearance. At the births of thousands of babies each year in the United States, the obstetrician can’t pronounce, It’s a girl! or It’s a boy! but must confess, I’m not sure what it is. Like Barbara, some appear to be born as girls but develop as boys at puberty. Some have a vagina and female external organs but lack such internal organs as ovaries and fallopian tubes; instead, they have certain male internal organs, like seminal vesicles, as well as testes hidden up in the body. 

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