DADDY'S LITTLE GIRL

By MICHAEL D. LEMONICK

Girls who suffer from the rare genetic disorder known as Turner's syndrome are a little shorter than average, have a thicker neck and usually can't have children. Otherwise, there's nothing especially striking about them--except that often they're socially inept. They butt into conversations. They misread facial expressions, tones of voice, body language. They're insensitive to others' feelings.

They act, in other words, a lot like boys. Why this should be has eluded science for decades. The answer, it turns out, may be in their genes, according to a report in the current issue of Nature. Turner's girls--and boys of all sorts--may get their social ineptitude from, astonishingly, their mother. Even more surprising is the implication that normal girls inherit their poise--and perhaps even their famous intuition--from their father.

It isn't as nutty as it sounds, given the genetics of gender. Boys, by definition, get one X chromosome from their mother and one Y from their father. Girls have two Xs, one from each parent. Girls with Turner's syndrome have only a single complete X, and it can come from either Mom or Dad; modern genetic tests can reveal which.

In the new study, a team led by research psychiatrist David Skuse of the Institute of Child Health in London ran those tests on 80 Turner's girls and then evaluated their social skills. It turned out that the ones with Mom's X were far more inept than those with a paternal chromosome.

This all makes sense, Skuse and his colleagues suggest, if you postulate a gene--or, more likely, a cluster of genes--on the X chromosome that governs social skills, and if those genes are activated only when they're passed on by the father. This phenomenon, called genetic imprinting, is known to occur in humans. Thus, says Skuse, boys are genetically destined to be inept because they get their X chromosome from Mom. Girls, by contrast, are socially adroit because they get one X from Dad (not that it did him any good, since he got it from his mom).

So how does Skuse explain the existence of sensitive men and insensitive (but non-Turner's) women? He doesn't. A social gene, he says, only sets the stage; how the players turn out depends on their environment. Even girls with Turner's syndrome can be taught social skills, he says. "But one has to recognize why they're not very good at them in the first place."

If it holds up, Skuse's theory might also explain why boys are more likely than girls to develop autism and attention-deficit disorder--conditions that involve difficulties in interacting with others. But until those social genes can be isolated, Skuse's theory remains just a theory.

One point in its favor is that it makes evolutionary sense. In hunter-gatherer tribes, women with strong social skills would presumably have had an advantage in attracting mates. Men in those societies, by contrast, might have been better off without acute sensitivities. After all, says Skuse, "being somewhat less empathic is an advantage if you are going out to kill somebody."

--By Michael D. Lemonick. Reported by Kate Noble/London

With reporting by KATE NOBLE/LONDON