Clues From Transsexual Rats

In at least one animal, the laboratory rat, nature seems much more important than nurture in determining sexual orientation and behavior. At the University of California, Los Angeles, neuroendocrinologis t Roger Gorski is learning exactly what little boy rats are made of.

First of all, they need testosterone and plenty of it early in life. Gorski and his team have found that if they castrate rats just after birth, the animals will exhibit behavior typical of a she-rat with the hots: arching their backs, flexing their tails and allowing other males to mount them. But by injecting these neutered males with...

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