Traditional religion-based morality would not have survived if it didn't offer some evolutionary advantage to people who espouse it. More radically, a gene or meme that compels you to "kill everyone who doesn't have this gene or meme" may cause itself to become more prevalent. Less radically, a gene or meme that instructs you to behave in ways that help survival will also cause itself to become more prevalent, even if the reasons the meme uses to convince you make no sense.

The reasons for traditional morality, indeed, do not make any sense. For the most part, we aren't even given any reasons. We're told to abstain from promiscuity because that's moral. The reason it is moral is because it's moral. We don't question the Book. The Book says so.

Now it's one thing to want one heterosexual partner for your entire life; that's a legitimate preference that there's nothing wrong with. But it's a whole other thing to judge people and try to prevent them from making different choices, as many voters around the world seem keen to do.

Traditional morality puts the cart ahead of the horse. There are valid reasons why heterosexual monogamy is better for your genes' inclusive fitness than promiscuity. The reasons, however, are technical. They have their limits. They can be defeated, and if they were defeated, there would remain no reason why people should not be promiscuous, unless they simply don't want it.

If we had full control over disease, and could stop it in its tracks; if we had full control over fertility, with no ill side effects; then promiscuity would not be an issue. That would be a good thing. Your opinion might differ, but the way I see it, monogamy is not very interesting, nor very rewarding. Promiscuity is both more interesting, more rewarding, and more challenging. It's just that... it is slightly worse for your reproductive fitness, for reasons that are unfortunate but quite avoidable. If only people would stop objecting to it on grounds that make no sense.

At this point, you might think I'm going to start talking about HIV. Or syphilis. Or chlamydia.

I'm not.

Those are all solved issues. As long as it's detected, bacterial disease such as syphilis, gonorrhea or chlamydia can be cured with a pill. If it's detected, it is less of a health issue than the flu.

HIV is still a burden, but it spreads much less readily than other disease. If we wanted to, we could defeat it with testing. Even if not using condoms, HIV can take more than a year's worth of vaginal intercourse to spread to another person (though it might also spread fast). For the purpose of stopping it as an epidemic, it would be sufficient to test the entire population a few years in a row, at least once per year. The tests would be cheaper per person than a year's supply of birth control. We wouldn't even have to draw blood, an oral swab would be enough. It would eliminate the risk largely completely.

The Human Papilloma Virus, HPV, is an unsolved problem.

HPV comes in multiple strains, many of which are very common. Some are innocuous. Some cause genital warts, but no other problems. Some can lead to cancer.

Recent research has shown that certain strains of HPV are responsible for an increased incidence of various types of cancer in people who have had more than a few sexual partners. Before widespread PAP testing was introduced, cervical cancer is said to have been a leading cause of death in women. Virtually all cervical cancer has been shown to be caused by HPV.

Not only that, but a history of more than a few oral sex partners increases your chance of oral cancer multiple-fold. This is caused by HPV. Having had receptive anal sex increases your chance of anal cancer by a factor of seven. That is caused by HPV as well.

You don't have to be especially promiscuous to expose yourself to this. You don't have to have had hundreds of sexual partners. It is enough to have engaged in serial monogamy. It is enough to have had one partner who had others before you. It is enough to have had departed from traditional monogamous morality in the most minor way.

What we should be doing about this is supporting research and taking steps to eliminate disease. Imagine that there were no STDs, or that they would not pose a problem. Imagine that all birth control is reliable and has no side effects. It would be safe to have sex with anyone, anyhow, anywhere. That would be a good thing. There would be no support for jealousy. If your partner had sex with someone else, she wouldn't be exposing you to anything. So why should you be complaining?

Since people are being promiscuous already, and aren't going to stop being so due to health risks, solving these health risks would be a good thing.

But then we have all these people who put the cart in front of the horse. People who read it in a Book that we were created to serve morality, instead of moral guidance having been invented to serve us. People who think that monogamy is a value in and of itself, regardless of circumstance. People who think that others should be punished for their promiscuity, whether or not it causes ill. People who want to actively impede progress in solving of sexual health risks, for fear that lifting barriers to promiscuity will... cause more promiscuity! People who don't want girls vaccinated against HPV because that might lead to them having more sex. (It doesn't - and if it did, it isn't even a bad thing.) People who don't want others to use condoms to protect from HIV, because they feel that's giving people an excuse to be promiscuous. People who think that the promiscuous deserve to die, because monogamy is all-important.

These people are nutcases. They are insane. They don't mean to be evil, but due to what they say and do, they are.

We need research. We need action. People were, are, and will remain promiscuous. That's not bad, in and of itself. What's bad is that it has ill side effects. We need to solve them.