Wonder woman

Their health advantage has long been chalked up to hormones. Now scientists are starting to explore the DNA within each cell, and they’re finding some protective benefits to having a double dose of the X chromosome, as females do, compared with the X-Y combination that males have.

But biology alone can’t keep a human being moving forward through heartbreak. Social and behavioral scientists, too, are finding that the networking skills first picked up in caves and passed on through millenniums of grain- and berry-gathering serve women today in getting through abuse, abandonment, infertility, divorce, widowhood.

A female’s biological advantage begins in the womb. There, the fertilised egg that becomes a girl gets a double dose of the X chromosome, while the egg that becomes a boy gets an X and a Y chromosome. In both sexes, each cell carries the individual’s genetic code. In men, that’s made up of genes on 22 pairs of chromosomes, and one pair of mismatched sex chromosomes, an X and a Y. It’s the same for women, except each cell carries two copies of the X chromosome. Yet no one can survive with two working versions of the X.

‘‘Females aren’t allowed to have twice as much gene product, so we turn off one chromosome,’’ says Migeon, whose work on the topic was published in the March 22/29 issue of the Journal of the American Medical Association. ‘‘It’s random. In half your cells, it’s the mother’s X, in the other half it’s the father’s.’’ So women end up with two types of cells. A number of genetic diseases originate on the X chromosome: colour blindness, muscular dystrophy and haemophilia. With only one X, boys might get just the defective cells, while girls get a mixture of normal and defective cells—a backup system to prevent some diseases.

Whatever the health problem, women invariably discover it sooner. Their bodies send them to doctors’ offices regularly for Pap tests, contraception prescriptions or prenatal care. ‘‘Women look after themselves from the age of 11 because they start to bleed,’’ says Sebastian Kraemer, a child and adolescent psychiatrist in London whose research on the flip side of resilient females, ‘‘The Fragile Male,’’ was published in the British Medical Journal in 2000. Men, short of accidents or health crises, are traditionally no-shows in doctors’ offices.

Women early on establish lifelong patterns of attention to their bodies, including check-ups, preventive screenings and ears tuned to medical advice. Biology and medical visits get women off to a good start. Then a woman’s psychological need to ‘‘tend and befriend’’, Taylor found, can protect her through hard times more effectively than the much-studied counterpart impulse in men: ‘‘fight or flight”. The lucky children benefit from the caretaking. But some of those who aren’t so lucky, remarkably, figure out how to compensate.

After 25 years of research and analysing more than 1,000 studies, Taylor found that early maternal nurturing can have an extraordinary effect on children. ‘‘A mother’s tening can completely eliminate the potential effects of a gene,’’ she says. Risk for a disease, like depression, can fail to materialise, and so can an inborn propensity to crumble under stress.

The female instinct to call in the helper troops, that network of girlfriends, sets up a chemical cycle unique to women. When females feel stress, Taylor says, the hormone oxytocin is released. That encourages them to protect the kids and start the telephone tree going. Contact with children or friends releases more oxytocin, further calming them and everyone around them. The hormone works better at reducing stress for women, Taylor says, because estrogen apparently enhances the action of oxytocin, while testosterone seems to reduce its effect. (Susan Brink)