I never thought of popularized science writing as potentially dangerous, even after I started writing "Carnal Knowledge" - a sex-themed column about the natural world and humanity's place in it.

Sometimes the accusations show up in our letters section. Others go directly to my in-box. Some letter writers say they're Christians, others not. One self-described liberal said I should know it's not just conservatives who had to cancel their subscriptions to keep their children safe from my column.

None articulated the type of harm I was inflicting or the mechanism by which my column was doing said harm. Perhaps they assumed it's obvious that terrible consequences will ensue if an innocent child seeking the comics page stumbled across the sex lives of honeybees, the secret history of the vibrator, or the evolution of the orgasm.

Let's reexamine that assumption: that terrible consequences are self-evident. What does the science say? Is there any evidence that information relating to sex hurts children?

If anything, I'd think children benefit from learning about science, clean or not. But then, I'm no child psychologist. Nearly everything I know about children comes from having been one in the early '70s.

Back then, enterprising children could pretty easily sneak peeks at Playgirl, Playboy and other magazines featuring naked grown-ups. Most convenience stores carried them, and some were more tightly watched than others. Airports were especially lax in supervising their porn racks.

I never felt harmed by any of this, or by the contraband copies of The Joy of Sex and other how-to sex books that would mysteriously disappear from the bookshelves of the less observant parents of my sixth- and seventh-grade classmates. But perhaps I was too close to the situation.

So I've turned to experts from psychology, anthropology and child development to educate myself on children and how they should and shouldn't learn about sex.

Scientists generally avoid questions such as "Is behavior X or influence Y corrupting or harmful?" It's too fuzzy to qualify as a testable hypothesis, so they usually look for a specific connection to heart disease or obesity, herpes or teen pregnancy.

Psychologist David Bickham said a recent study showed a strong correlation between teen sex and the degradation of women in popular music. "It goes along with the idea that it's really about the context," said Bickham, who works out of the Center for Media and Child Health, run by Harvard and Children's Hospital Boston. But lyrics about sex per se didn't have the same effect.

Journalism professor Jane Brown of the University of North Carolina led an earlier study that found children exposed to the most sex in the media were more likely to have sex before they turned 16. She looked at music, movies, magazines and television.

She said for many children and teenagers, the media and friends make their best sources of information. "Most of the other sources where kids might learn about sex are not talking," she said. "Parents aren't talking, schools aren't allowed to talk, and churches are saying, 'Just say no,' " she said.

In Europe, she said, there's much more open conversation about sexuality, more comprehensive sex education - yet European children start having sex later than Americans and they have fewer diseases, abortions or unwanted babies.

The issue in the United States is not that the media discuss sex but rather the way our media deal with sex, she said, presenting it in a glamorized and sanitized light. With a few exceptions, movie and television characters appear too swept up by passion to talk about birth control or sexually transmitted diseases or whether they're in a monogamous relationship, she said, and children can be misled into thinking there's something wrong with them if they stop the action to deal with such messy concerns.

It's not exposure to facts about sex but child abuse that lays the foundation for later sexual problems, said Galdino Pranzarone, a psychologist at Roanoke College. Pranzarone studies pathological paraphilias - fetishes that go beyond a healthy sense of adventure to limit or distort a person's ability to enjoy sex or form healthy relationships.

Children, he said, often explore their own bodies and those of other children by "playing doctor" and related games. This is called "juvenile sexual rehearsal play" and is found in all cultures and in other primate species. "The word here is normal and not pathological," said Pranzarone.

Many children discover masturbation with no help from the outside world. Thanks to the ubiquity of ultrasound, he said, we now know some engage in it before they're even born.

But that's all based on relatively new science. During the 18th, 19th and early 20th centuries, the mainstream medical community considered masturbation an epidemic, leading to debilitating illness, dementia and, yes, blindness. These were no old wives' tales: Some doctors even reported fatalities. But when researchers finally did some studies in the mid-20th century, they couldn't find any of these health risks, and in 1972 the American Medical Association published a paper declaring masturbation normal.

In cross-cultural studies, Pranzarone said, researchers found that people from societies that take a casual attitude toward that childhood tendency to play doctor have healthier sex lives than those who punish children for it.

Indeed, he said, the trouble comes when parents catch children masturbating or playing doctor and terrify, threaten, beat or otherwise brutalize them.

For example, he said, one female subject could enjoy sex only in masochistic relationships with abusive men. He found her problems traced back to an incident in which her mother caught her masturbating in the bathtub, "freaked out," and inflicted a brutal punishment.

Pranzarone said he had observed an inverse relationship between a society's openness about sexuality and the incidence of pathological paraphilias. They are rare in Nordic countries, for example, where there's less of a taboo associated with sex and nudity.

Similar findings come from anthropology, said Chris Kovats-Bernat of Muhlenberg College. In many Asian and African countries, crowding forces families to sleep together in one room. Inevitably, parents have sex when they think (or at least hope) their children are asleep.

But here in America, it's more common for parents to try to explain sex in a "birds-and-bees" talk, given at some predetermined age. The experts say it's better to let children set the pace. You may be surprised, say some, to realize what your children already know.

"I don't think there's any right or wrong time," said Myrna Shure, Drexel University psychologist and author of the book Thinking Parent, Thinking Child. If the child is "reading about something and is interested enough to mention it, then he's ready to talk about it." But she cautioned that parents should be brief, honest and factual.

"Typically, children will bring up questions," Schure said. "That's a signal they're ready for that one question." Children tend to filter out information that goes beyond what they're ready to process.

And not answering is still sending a message, said Luis Garcia, a psychology professor who teaches a course in sexuality at Rutgers University. "Even if you say, 'I'm going to avoid sexuality,'... then you are, in effect, teaching that sexuality is something to be avoided."

"I don't know why people are afraid of biology," said Roanoke's Pranzarone. "There is no age in childhood that is too early for a child to learn the truth about anatomy, courtship, sexuality, arousal and pleasure giving and receiving," he said.

Donna Tonry, a psychologist from LaSalle University, said the danger came when parents got angry at children for learning about sex from outside sources. "If this occurs, depending on the level of upset and how that parent handles it, some damage may occur. The child may feel that he or she did something wrong just by knowing information."

Why are some parents so concerned about their children's knowing too much about sex? Evolutionary psychologists say we carry some innate urge to fret about our children's sex lives. In many societies, parents get to arrange marriages and thereby exert full control over their children's reproductive futures.

Your children carry your genetic legacy, after all, so it makes some sense that evolution would favor parents who take an active interest in where that legacy goes.

None of the experts could cite studies on the consequences of children accidentally seeing adult-oriented newspaper science columns. Harvard's Bickham said he had never considered the idea of studying the impact of the media's dissemination of factual knowledge - whether it's animal sex or the evolution of human sexual physiology and behavior.

Nobody has, to his knowledge, conducted a controlled scientific study to see what happens if preteens learn the latest theories on the evolution of the female orgasm, the genetic roots of homosexuality, the evolutionary biology of the penis, sexual conflict in giant squids, or the effects of testosterone on female to male transsexuals.

So in the end, there's no evidence of harm - but no controlled clinical trials to prove safety either. Overall I'm relieved. And if you think your Joy of Sex might have disappeared for a few days at some point, you can probably relax, too.

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