Western thought about sex -- from the story of Eve to Aristotle's belief that girl babies arise from cooler sperm -- has been tainted by the notion that the female is a kind of imperfect or unfinished male.
Medical science, however, has gone from treating women as though they were simply smaller men to realizing that sex confers many more differences than those that are related to reproduction.
In contrast to the feminist premise that women can do anything men can do, science is demonstrating that women can do some things better, that they have many biological and cognitive advantages over men. Then again, there are some things that women don't do as well.
One of the less visible, but theoretically very important differences, is the larger size of the connector in women between the two hemispheres of the brain. This means that women's hemispheres are less specialized: A stroke that damages the left side of the brain leaves men barely capable of speech, while the same damage to a woman's brain is far less debilitating since she can use both sides for language.
Although there is no hard evidence, the larger connector may also account for a woman's tendency to exhibit greater intuition (the separate brain halves are more integrated) and a man's generally stronger right-handed throwing skills (controlled by a left hemisphere without distractions).
Mary Catherine Bateson, the cultural anthropologist and a former president of Amherst College, has described women as "peripheral visionaries" able to follow several trains of thought (or children) simultaneously.
Men, by contrast, seem more capable of focusing intensely on single topics. Our strengths, then, come from our differences rather than from our similarities.
Science and medicine are finally realizing that the differences between men and women necessitate developing distinct therapeutic treatments addressing the specifics of our physiology.
For example, doctors like Dr. Susan G. Kornstein of the Medical College of Virginia's department of psychiatry are advocating the use of sex-specific assessment and treatment of psychiatric disorders, like depression.
In a recent paper published in the Journal of Clinical Psychiatry, Kornstein points out that while depressed men seem to respond best to drugs that affect two neurotransmitter systems, those involving norepinephrine and serotonin, women respond better to drugs that affect only the serotonin system.
These differences in the therapeutic benefits of drugs not only underscore the need for medicine to go beyond giving women tapered doses of whatever is being prescribed for men (a latter-day offshoot of the women-as-incomplete-men theory), but support the idea that men's and women's brains do not function the same way.
Indeed, it is not only our brain functions that apparently diverge, but just about every aspect of our physiology. The way we metabolize alcohol and drugs, the way our circulatory system works and how resistant we are to infection are all affected by our sex.
In utero, girls and boys are chromosomally different; one might say that the determinant of maleness, the Y chromosome, named for its shape, is "missing" something that the female determinant, the X chromosome, has. But they look identical.
The development of characteristic male and female sexual genitalia at birth and of secondary sexual characteristics like breasts during adolescence results from influxes of hormones, including estrogen and testosterone.
But the hormones we once thought were important only for pregnancy, lactation and sexual drive have profound effects on just about every organ in the body.
For example, recent research demonstrates that while men begin to suffer from coronary artery disease earlier in life than women do, women are more likely to die of coronary complications once they are afflicted. Men are also more prone throughout most of their lives to high blood pressure, but as women get older, this advantage disappears.
The delayed onset of cardiovascular disease in women may be linked to the fact that the female hormone, estrogen, which is produced mostly by the ovaries, protects the circulatory system from disease.
Differences in the quantities of estrogen, essential for the organization and maintenance of tissues and organs in both sexes, play an important role in brain development and appear to be the reason that men's brains are bigger, but women's brains have more neurons.
Estrogen makes blood vessels more elastic, stimulates them to expand and allow good blood flow, and prevents cholesterol accumulation inside blood vessels.
As women age, however, they lose the protective benefits of estrogen because, in a rather dramatic fashion, their bodies stop producing it.
At the same time, some treatments that are used to prevent cardiovascular disorders - aspirin, for example -- are less effective in women.
Reporting in a recent issue of the International Journal of Fertility and Women's Medicine, Dr. Marianne Legato of the Columbia University College of Physicians and Surgeons notes: "Although XTC aspirin use is associated with less frequent myocardial infarction in both men and women, it does not decrease the risk of stroke in hypertensive women, as it does in men."
A number of naturally produced compounds fluctuate more in women than in men: steroids, for example, which are infamous on the street for their role in developing muscles and shortening tempers.
It turns out that steroids, a class of compounds that includes sex hormones, may play an important role in the mood swings of menstruators. These hormones directly affect brain cells.
The neuroactive steroid allopregnanolone, made from progesterone, dampens the sensitivity of brain cells; it works like benzodiazepine drugs, most familiarly, Valium. When the progesterone level is high, a woman is calmer. When it is low, she may feel more anxious and irritable. Moreover, women with PMS become insensitive to the calming effects of Valium-like drugs.
There is a growing consensus that these steroids produced by the sex organs are responsible for the greater incidence of mood disorders and depression in women. And a growing body of research is pointing to a role for other, similar steroids in memory, stress and alcohol abuse.
In keeping with the increasing recognition that some powerful mind-altering substances are internally produced by hormones, it is no wonder that adolescence is often a time of emotional turbulence. You cannot "just say no" to your body's genetically timed release of mood-altering sex hormones at puberty.
What society considers "recreational" drug use, which often begins at adolescence, may sometimes be motivated by an effort to self-medicate, changing or reversing the effects of sex hormones and neuroactive steroids. The notorious mood swings of adolescents may very likely reflect the body's adjustment to new concentrations and combinations of these compounds.
Lester Grinspoon, an associate professor of psychiatry at Harvard University Medical School and an advocate of the medical use of marijuana, points out that marijuana has long been known as a palliative for the psychophysical pains of menstruation. Queen Victoria, according to her doctor J.R. Reynolds, used it for that purpose.
Curiously, one of the few medical studies on marijuana suggests that its use lowers testosterone levels in men, although this finding has been disputed.
Perhaps this drug, among others, interacts with or works in a way similar to the hormonal and neuroactive steroids.
In any case, women, who are twice as prone as men to depression, and who have a higher body fat-to-muscle ratio and more hormonally distinct brains, cannot be expected to respond to drugs, legal or illegal, in the same way men do.
Clearly, humans have learned that the two sexes, subtly different, develop differently, respond differently to certain drugs and see the world in different ways.
As the French say, vive la difference.
Dorion Sagan is the co-author, with Lynn Margulis, of "What Is Sex?" and "Origins of Sex: Four Billion Years of Genetic Recombination." This article was distributed by New York Times Special Features.
Pub Date: 6/28/98