There are a lot of areas of human sexual behavior that are pretty clear cut. For instance, there is little or no scientific disagreement regarding the evolutionary advantage for males to desire and pursue multiple sexual partners. For that matter, there’s practically no disagreement that casual sex, for males, is evolutionarily beneficial. Every time a man has intercourse with a woman, he has a chance to increase his genetic heritage, and if he can do so without investing anything more than a few minutes of his time and a tablespoon of bodily fluids, so much the better.
Similarly, it’s pretty clear cut that it is to a woman’s advantage to be more sexually selective than males. Women who secure long term male companionship are substantially more likely to pass on their genes than those who don’t. While a man can theoretically father dozens or even hundreds of children at once, a woman goes at it one child at a time (excepting, of course, twins, triplets, etc, which are relatively rare.)
There’s a puzzle, though. Evolution weeds out that which does not work. If we see a behavior that is ubiquitous among a species, we must explain it as a behavior that promotes genetic success in some way. Bearing this in mind, we are forced to admit that in order to explain male promiscuity and casual sex, we must explain female promiscuity and casual sex. In other words, if females had not been having casual sex throughout our evolutionary history, males would not have been able to have casual sex. The desire to have casual sex would have been largely weeded out. (Consider that if females do not select males who try to be promiscuous, such males would not reproduce, and all that would be left would be males that do not try to be promiscuous.)
Here, I must caution the reader against “should thinking.” This is not an article about keeping promises or being a person of integrity. It is about evolutionary origins of behavior. We must not suppose that we humans are immune from the truth of what we do. No amount of pontification about how we should be monogamous can change the fact that we are not monogamous as a species. Bearing this in mind, we observe that human males do attempt to have casual sex — frequently. More importantly, they succeed quite often. This means that there are a lot of females who engage in casual sex, which in turn points to an evolutionary benefit to their doing so.
Because the following theories are not politically correct, I think I must make more disclaimers. First, I will reiterate that what we have done our entire history is not necessarily what we should do now. Second, we should remember that a thing can be true and politically incorrect or personally uncomfortable. We must not shy away from an idea simply because we are repulsed by it. Bearing these facts in mind, let’s examine the best theories for female casual sex.
We must note that human sex is social as well as reproductive. With concealed ovulation, and only a few days of fertility each month, females are capable of having a great deal of intercourse without conceiving. (Again, since we are this way, there is some function to it. It accomplishes something evolutionarily beneficial.) Even casual sex is a bonding experience of sorts. There’s a reason humans have booty-call buddies. It’s easier to convince a woman to have casual sex after she’s already consented to it in the past.
Having noted the social significance of sex, we should also note that emphasis on virginity is not a ubiquitous human trait. Some societies consider non-virgins to be unmarriageable, but others do not. In fact, some, like the famous French Polynesian natives encountered by Gauguin, are distinctly unconcerned with whether or not their wife is a virgin. As we survey known cultures, we find a rather direct correlation between dominant patriarchies and emphasis on virginity. As cultures become more egalitarian, it becomes less important. The conclusion that seems to make the most sense is this: Humans do not have an “instinct” for virginity. This being the case, we can guess that women might have sex with men and then reject them as potential mates. Remember that through much of our evolutionary history, we were probably not aware of the connection between sex and babies. Before our brains grew dramatically in size, we simply acted on our desires, without the kind of forethought we are capable of now.
So here is one theory: Women try out mates by having sex with them. There’s considerable circumstantial evidence to support this idea. For one thing, close intimate contact such as kissing is an instant compatibility meter. Similarly, women across all cultures report sharp increases or decreases in the attractiveness of men after having one sexual encounter with them. It seems that such close contact, and the exchange of bodily fluids during intercourse might provide chemical clues to genetic compatibility. This is strong support for the idea that women have historically selected men based on casual sex. (Remember, even today our definition of casual sex is fluid. It’s only casual sex if it doesn’t lead to a relationship!)
But there’s more to the story than just discovering genetic compatibility, and this is where things can get a little nasty for idealists. Women don’t just receive genetic material from men. They receive two more things — protection and resources. We simply can’t ignore the fact that through virtually all of human history, women have needed the protection of men. Whether the threat was rival consorts, enemy tribes, or nonhuman predators, women have always been better off when they have had men to protect them physically. The evidence for this is disturbing and vivid. In tribal and other primitive cultures all over the world, women are treated differently depending upon their level of male protection. The Yanomamo are known to capture women from rival tribes after killing the males. (Also, recall that Jehovah commanded the Israelites to do the exact same thing on numerous occasions.) Some of these women become wives or concubines, and some do not. If another tribe should attack a tribe with captured women, the men will not raise a finger to help a woman who is not bonded in some way to a tribesman. They will simply allow the rival tribe to capture and rape her.
We can also find clues to our protection of females by looking at our close relatives. In many primate species, females have close relationships with multiple males. In such societies, when violence arises, “popular” females are protected by multiple males, and have the smallest chance of succumbing to violence. Furthermore, when a female’s partner dies (which is not at all uncommon) she will usually turn to one of her special male friends as her new primary mate.
Humans today do the same kind of thing. I am reminded of a comedy skit by Chris Rock where he joked about relationship breakups. Men know, said Rock, who their ex is going to have sex with next. Women always have a “Number Two” lined up just in case things don’t work out. They’ve been calling him for months to gripe about you, he said. While there is certainly some hyperbole at work here, it is a fundamental truth. Across all cultures, when women are given the freedom to be so, they are keenly aware of their future mating possibilities.
Human evolution apparently designed women to rank males by desirability, and to foster potential relationships with other males in case their mates die or abandon them. Furthermore, the now proven unfaithfulness of women coupled with females’ considerable reluctance to have sex with a stranger paints a clear picture. Women have typically kept lovers and potential lovers on the side. Again, we can look at current human behavior and see the truth of it. Whenever a woman is threatened in a social situation, all of her male friends get a rush of testosterone and hurry to her aid — not just her boyfriend or husband. We can guess that now, as well as throughout history, there’s a reasonably good chance that the female has slept with or will soon sleep with one or more of these “second choices” as a social bond, as well as to increase her chances for securing a mate in the future should the need arise. (We also note the very strong desire in many women to “stay friends” with ex-boyfriends. We shouldn’t gloss over this tendency! Ex-boyfriends are very protective, too.)
Finally, we must address payment for sex. Rather than sugar coat this, I’ve decided to just state it in evolutionary terms. Humans, like a host of other animals, give females gifts, and they return the favor by offering their bodies. Through most of human history, money did not exist. In fact, accumulated wealth did not exist, either. Yet, women across cultures and throughout history, have demanded sizable gifts from potential suitors. The fact is, women are attracted sexually to men who give them things. We must conclude that before money, women still demanded payment of some sort from potential suitors, whether it was meat, jewelry, shelter, or anything else of value.
There is a shift in women’s attitudes when it comes to casual sex, too. Put simply, across all cultures, women view men who lavishly and frivolously spend money as desirable for casual sex but undesirable as mates. Furthermore, women across all cultures are immediately turned off to potential casual sex partners who seem frugal. The implication is clear. Women want to get something out of casual sex — and I do mean a tangible resource. The most logical explanation is that women prefer their mates to be thrifty, thus maintaining the maximum possible resources for offspring, but they prefer casual sex partners to be frivolous so that they get the maximum possible reward for the brief duration of the relationship.
In order to think about this objectively, we need to divorce ourselves from the stigma of prostitution for a moment. In our evolutionary past, women needed and desired males with resources. Marriage didn’t exist. What existed was the raw fact that women without resources died. Women all had one thing that all men wanted — sex. It was an evolutionary inevitability that as society grew more complex, women developed more complex ways of exchanging sex for resources. As we survey the current human population, we see myriad examples of them doing so, from pornography to escorts to trophy wives of old rich men to golddiggers to women climbing the corporate ladder one penis at a time.
We must also dismiss the myth of women marrying down for love. While it’s true that occasionally a woman will marry significantly below her capacity, it is very rare. If it were commonplace, it wouldn’t make a good story! Across all cultures, women demand dowries or wedding rings or bank accounts deserving of their place in the hierarchy of available single women. Prostitutes with no teeth and three separate C-section scars give blowjobs for five dollars or a hit from a crack pipe. Escorts who speak three languages and look like supermodels get ten thousand dollars a night. Daughters of presidents and movie stars do not marry poor janitors or Burger King employees. They marry men with similar social and economic standing.
Marriage is a sexual contract, and women demand proper payment for entering into marriage. It’s not polite to say so, but it’s true. Women also have casual sex, and when they do, they tend to get something out of it, whether it’s a bar tab, a ride in an expensive sports car, or a weekend getaway in Paris. Of course, there are some casual encounters that are simply about lust, and no resources or protection is given. However, we cannot overlook mountains of evidence that these things are crucial in our evolutionary history. These are very likely to be the primary reasons why women developed the desire to engage in casual sex: Trying out potential mates, securing protection from multiple males, and securing resources from multiple males.
In order to avoid accusations that I am promoting or condoning any kind of sexual behavior, let me say again that I have no intention of doing so. I am only attempting to explain our desires to engage in casual sex, and I make no claim as to the desirability of the outcome of engaging in such behaviors. I will admit that personally, I can find no solid line of demarcation between trading sex for marriage and trading sex for a weekend in Paris, other than the length of the contract. I will also admit that I cannot find a concrete difference between having a one night stand after accepting a hundred dollars worth of drinks and dinner and accepting a hundred dollars cash, either. Still, these are topics for another discussion, and I don’t wish to argue them here. Suffice it to say that evolution appears to have programmed us for short term sex, and has given men the desire to pay for sex, and women the desire to accept payment. For the time being, we will leave it at that.