A while back we promised to respond to the sexperts featured in a story on Slate.com on things about sex that confuse even bona-fide sex experts. We hope you (and they) will find our take on these issues provocative and possibly even illuminating. As we wrote in Part I, if our model holds any water, we should be able to answer some of their doubt and questions in terms of what we've learned about prehistoric sexuality. Here's the second and final installment.

You can find the original article from Slate here and Part I of our response here.

Ian Kerner is the author of She Comes First, He Comes Next, and other sex advice books: "Why do most men still know more about what's under the hood of a car than the hood of a clitoris, and why, in our post-Sex and the City culture, are women faking it more than ever?"

Doesn't the premise of his first question answer the second? Also, we'd be careful about assuming most men know how their cars work. And how does he know that "women are faking it more than ever?" Still, reasonable questions.

Briefly, we strongly believe that modern societies generally teach and insist upon sexual ignorance. Clearly, the situation isn't as bad as it was when people were being severely punished for masturbating a century ago (doctors used acid to burn away the clitoris) or imagining evil spirits fornicating with them at night two or three centuries ago -- but it's still pretty bad. Even Bill Clinton (hardly anti-sex) fired his Surgeon General for suggesting that masturbation should be openly discussed in schools. And our federal government is still in the business of insisting on abstinence-only education -- despite the voluminous evidence that it is substantially worse than ineffective. Even supposedly clear-thinking scientists are still arguing that human nature tends toward sexual monogamy! No wonder a lot of guys prefer to work on their cars -- it's a lot easier to get reliable information on auto mechanics than on the mechanics of love.

Em & Lo are sex and relationship writers and authors of Buh Bye: The Ultimate Guide To Dumping and Getting Dumped: "We've never been able to understand why virginity is still defined strictly in terms of penile penetration. Does that mean all lesbians are lifelong virgins?...."

Yeah, it does, at least as far as most religious authorities are concerned. This one's pretty easy. Virginity is an important concept only in societies that are concerned with property rights. But the fact that just about any society around at the moment fits this category doesn't mean this concern is a universal human preoccupation, as many evolutionary psychologist argue.

Societies that aren't founded upon a sense of the importance of personal property don't even have a word for "virginity." Despite their tragically low numbers today, such pre-agricultural societies were ubiquitous for most of our existence as a species. This illuminates the point that virginity really isn't about sex; it's about paternity certainty. So any sex act that cannot result in pregnancy isn't really at issue.

Here in Spain, where there's a large North African population, more than a few of our male friends have had encounters with Moroccan or Tunisian women who were game for anything but vaginal sex -- so they could keep their "virginity" intact for marriage.

Simon LeVay is the author of The Sexual Brain and Human Sexuality: "I'm co-author of an undergraduate human sexuality textbook, so every few years I have to review the whole field of sex research to see what advances have been made. The most depressing area is that of "paraphilias," which are pathological sexual desires, often involving victims—everything from pedophilia to zoophilia, exhibitionism to sexual murder and cannibalism. What's depressing is that we seem to be making little or no progress in understanding the cause or treatment of these conditions. So victimization continues, and the perpetrators—nearly always men—are warehoused in state "hospitals" or exposed to ever more vindictive harassment in the community. Whoever figures out how to prevent their descent into deviancy, or how to give them back healthy, loving sex lives, will have alleviated untold suffering, and will have made that dark corner of my textbook a greater pleasure for me to write and for students to read."

First, we'd suggest that Dr. LeVay's definition of paraphilias is a bit extreme. Paraphilias are not necessarily "pathological," just unusual. You may be turned on by watching monster truck competitions on TV, or the smell of grilled cheese sandwiches. Those would be considered paraphilias, but hardly pathological -- at least, not by us. He refers to the ugliest possible examples (cannibalism!), but most paraphilias are merely harmless fetishes.

There's a little-known area of research involved with "erotic plasticity" that has revealed some very interesting information concerning paraphilias, fetishes, and so on. We explore this research in our book.

Essentially, the research suggests that males (of many species, including humans) seem to have a relatively brief period in their development when their sexual appetites are determined. We're not referring to sexual orientation, but to what turns them on, within that orientation. Once this developmental window, that's it. With humans, this period appears to be somewhere between five and twelve years of age. So, if an eight year-old boy makes a strong association between his emerging erotic feelings and the red shoes his teacher wears every day, that might get imprinted indelibly on his eroticism. He may not even remember why, but women in red shoes will always turn him on.

Women, on the other hand, seem to be much more flexible in terms of what turns them on. In other words, they have much greater erotic plasticity throughout their lives.

This may explain why virtually all fetishists are males. They are stuck with what turns them on and can't adjust it to changing realities as they mature. Hence, pedophiles are pretty much impossible to "cure." They'll never stop feeling what they feel. Still, as Schopenhauer said (certainly not thinking of paraphilias), "A man can do as he wills but not will as he wills."

To return to Dr. LeVay's original concern about the origins of these paraphilias and how to reduce them in our society, with this information about erotic plasticity, it becomes clear that the best (perhaps only) way to eliminate them is to stop exposing boys to destructive, violent, damaging situations. It's no coincidence that men who abuse children were virtually always abused themselves as children. A boy who is sexually abused is likely to form some inescapable association between that situation and his own eroticism. It's a chain that has to be broken using information and compassion.

Dan Savage is a nationally syndicated alternative weekly sex columnist (and our personal favorite sex-advice guru): "What I don't understand is ... gee, how people can be so willfully stupid about sex. Sex came first. Before marriage, there was sex. Before religion, there was sex. Before freakin' humans, there was sex. All human cultures, and all our fanciful religions, were constructed around sex, built to regulate and control sex, sanctify and elevate sex. But so many people want to start with culture or religion before they approach sex, as if the former can teach us all we need to know about the latter. Not true. We have to start with sex. I'm not arguing that we should do away with all regulations or controls, or that sex shouldn't be sanctified or elevated. But there are regulations and controls that are idiotic, products of a time when we didn't truly understand human hair growth—or physics or gravity or the movement of the planets—much less human sexuality, and they should be reassessed. I'm thinking of bans on prostitution, bans on same-sex marriage, the promotion of "normal" sexuality (meaning: no kinks), the cultural assumption that the ability to have sex without love is evidence of some sort of mental illness. In these areas, some of our attempts to sanctify and elevate sex run so counter to human nature that they cause nothing but misery."

As usual, we are in near total agreement with Dan. The only point we'd take exception to is his contention that "all human cultures... were constructed around sex...." As mentioned above, the control of sex really only becomes an issue when cultures are constructed around property. Before the advent of agriculture and property, there was no need to worry about which kids were created with the assistance of specific men. In fact, as we explain in our book, many (pre-agricultural) cultures still believe that a child can have several biological fathers and there are many societies in which sex is considered to be important, but hardly a central concern in life. Needless to say perhaps, these societies are far less concerned with controlling sexuality and thus find that it doesn't control them.

Dr. Ruth Westheimer is the author of 31 books about sex and relationships.
"I'm sure there are many, but one nagging one is what causes homosexuality. I admit, I am curious—but the real importance in getting to the bottom of this question is that the answer would be helpful to the homosexual community. I suspect that the cause is genetic, which would mean all those people who say that gays and lesbians can change to become heterosexual would have to sing another tune. Instead of trying to "fix" a situation that doesn't require fixing, they would have to learn to accept homosexuals. But I am not a scientist, so I can't set about finding out the etiology, the cause of homosexuality. All I can do is act as a cheerleader to encourage scientists to come up with the answer."

It's a good question, and one we don't explore much in this book. What comes to mind upon reading her thoughts is that it's probably a mistake to assume there is a single cause for homosexuality. It's likely to be a case of a genetic propensity joined with certain environmental factors -- both pre- and post-natal. Studies have shown that there appear to be clear genetic tendencies within families (if memory serves, it's the mother's brothers who are most likely to predict a boy's possible homosexuality), but other studies have shown that the fetal environment has an important impact on sexual orientation, too. Apparently, if a woman has had several sons previously, the chances of subsequent sons being gay increases. The suspicion is that this has something to do with hormonal levels in the amniotic fluid.

Dr. LeVay, whom we mention above, first burst into public consciousness when his research suggested that there are anatomical differences between the brains of straight and gay men, reinforcing the sense that sexual orientation is not something one chooses.