their focus from the role played by hormones in the mature organism to the role played by hormones in the womb. Working from guinea pig studies done two decades earlier by Soviet sex researcher Vera Dantchakoff, the Kansas team sought to learn the role played by the hormones that bathe a developing fetus’s brain and nervous system. Earlier researchers had shown that, in humans, in the early stages of gestation, the male and female fetus’s internal and external sex organs are identical to one another. Between six and eight weeks, however, changes start to take place. If the fetus’s cells bear the male (XY) chromosome, the fetal gonads differentiate as testicles, which begin to pump out testosterone. This prenatal androgen is the agent that masculinizes the developing fetus’s external genitals—turning the undifferentiated genital tubercle into a penis, causing the open genital sinus to fuse along the midline and form the scrotum, into which the testicles descend—and at the same time masculinizes the internal reproductive system by spurring the growth of the seminal ducts (another testicular secretion suppresses growth of the rudimentary female internal structures). If, on the other hand, the fetus bears the female (XX) chromosome, the gonads develop as ovaries, no testosterone is produced, in the absence of which the external genitals and internal anatomy differentiate as female, the genital tubercle develops as a clitoris, the genital sinus remains open and becomes the entrance to the vagina, and the internal structures develop as fallopian tubes and uterus.
The question for the Kansas team was whether these prenatal hormonal effects on the anatomy were mirrored in the brain. To find out, they set about creating a cohort of hermaphrodite guinea pigs by injecting large doses of testosterone into the wombs of pregnant mothers. When exposed to testosterone at a critical stage in fetal development, the female guinea pigs were born, as expected, with clitorises enlarged to the size of penises. The researchers then set out to learn if the masculinization of a treated female’s anatomy was matched by a corresponding masculinization of her sexual behavior.
In observing the treated females as they grew from childhood to maturity, the team noticed something extraordinary. Not only did the treated females demonstrate an increased physical activity distinct from that of their untreated sisters, they also did not, in the presence of normal males, present their hindquarters for sexual penetration in the normal female in-heat posture known as lordosis. Instead, the testosterone-treated females (even those that showed no clitoral enlargement) attempted to mount their untreated sisters.
I spoke with team member Robert Goy, shortly before his death in 1999, about the breakthrough moment of his research career. His voice was charged with an excitement that suggested he had just made the discovery the night before. “We couldn’t schedule tests fast enough,” he told me. “We were testing every night—night after night after night—and getting data, and analyzing it, and reanalyzing it.”
Milton Diamond was in the thick of the research, performing adjunct experiments on the pregnant mothers to learn what, if any, influence the testosterone had on their functioning. Having come to Kansas hoping to learn something new and interesting about the action of hormones on behavior, Diamond found himself present at one of the most significant biological breakthroughs in sex research of the twentieth century.
There was concern among members of the team about how their professor, William Young, would react to the results. They knew him to be an adherent of the theories of psychosexual neutrality advanced just four years earlier by John Money’s team at Johns Hopkins. “Young was a great follower of John Money and the Hampsons,” Goy told me. “He had been thinking all this time that the organizing principle for sexual behavior was
The question for the Kansas team was whether these prenatal hormonal effects on the anatomy were mirrored in the brain. To find out, they set about creating a cohort of hermaphrodite guinea pigs by injecting large doses of testosterone into the wombs of pregnant mothers. When exposed to testosterone at a critical stage in fetal development, the female guinea pigs were born, as expected, with clitorises enlarged to the size of penises. The researchers then set out to learn if the masculinization of a treated female’s anatomy was matched by a corresponding masculinization of her sexual behavior.
In observing the treated females as they grew from childhood to maturity, the team noticed something extraordinary. Not only did the treated females demonstrate an increased physical activity distinct from that of their untreated sisters, they also did not, in the presence of normal males, present their hindquarters for sexual penetration in the normal female in-heat posture known as lordosis. Instead, the testosterone-treated females (even those that showed no clitoral enlargement) attempted to mount their untreated sisters.
I spoke with team member Robert Goy, shortly before his death in 1999, about the breakthrough moment of his research career. His voice was charged with an excitement that suggested he had just made the discovery the night before. “We couldn’t schedule tests fast enough,” he told me. “We were testing every night—night after night after night—and getting data, and analyzing it, and reanalyzing it.”
Milton Diamond was in the thick of the research, performing adjunct experiments on the pregnant mothers to learn what, if any, influence the testosterone had on their functioning. Having come to Kansas hoping to learn something new and interesting about the action of hormones on behavior, Diamond found himself present at one of the most significant biological breakthroughs in sex research of the twentieth century.
There was concern among members of the team about how their professor, William Young, would react to the results. They knew him to be an adherent of the theories of psychosexual neutrality advanced just four years earlier by John Money’s team at Johns Hopkins. “Young was a great follower of John Money and the Hampsons,” Goy told me. “He had been thinking all this time that the organizing principle for sexual behavior was
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