Are We Really Monogamous?

Most of what I've written so far about human sexuality has been rather erudite, and certainly doesn't answer many questions of what makes us go on dates and cheat on our spouse, or why we want so badly to get married when we're twenty-five. I promise things will be looking up very soon. In this very essay, we'll even talk about orgasms and the size of men's testicles. There's still a bit of science we need to deal with, but we're done with all the biology terminology. From here on out, it's all about when we have sex, why we have sex, and with whom.

I'm going to tackle human sexuality from both sides, male and female. This may seem the obvious choice, but just to be sure, let's remember that sex is competition. Males and females have their own interests, evolutionarily speaking, and we have hopefully dispelled the myth that human intelligence puts us above other animals. Like chimps and dolphins and killer whales, we are very intelligent social animals, and examining our behavior is the same as examining that of any other creature. If we see a pattern of behavior, there is a reason for it. Anything that exists is a product of evolution, including our intelligence and our incredibly complex society. If we look well into our past, we will understand the mechanisms behind our behaviors. If we are lucky, we will be able to take the lesson of sugar consumption to heart, and we will be able to make some educated statements about what we should do if we want to achieve a particular result. (If you didn't read about sugar, you must go back now and read What Does Sugar Have To Do With Murder?!)

So, on to the question of monogamy. Before answering decisively, I must make a distinction about the word itself. There are two very different ways of asking the question – that of a social scientist and that of a sociobiologist. An anthropologist who speaks of monogamy is talking about marriage, or whatever cultural equivalent there might be. A species is monogamous if males and females have one official partner. This does not take adultery into account, nor does it account for serial monogamy, which is the practice of having one partner for a relatively short period, and then moving on to another partner. On the other hand, a sociobiologist who speaks of monogamy is speaking of the actual practice of mating. A species is only monogamous if it really has only one sexual partner. Any mating is considered part of the equation, and social institutions are not considered.

For the time being, I will be using the sociobiological application of the word. When I speak of polygamy, I am speaking of the practice of having multiple sexual partners, regardless of institutionalized or cultural norms. Similarly, monogamy will only apply when a species really does mate with only one partner. Just as in our mental exercise with sugar cravings, we must first understand how we behave, and then we must understand why. Only then can we begin to look at ourselves as individuals and begin to think about goals and how we should act if we wish to achieve them.

Finally, then, the answer to the question. Are humans monogamous? The short answer is no. We are mildly polygamous. The long answer requires addressing the question from various points of view. Culturally, we have always focused on a single marriage between a man and a woman, but there are two unavoidable facts that we must not overlook, even if they are incriminating or cause us personal discomfort. First, though marriage has virtually always been between one man and one woman, mating has not. Since the agricultural revolution, powerful men have virtually always kept harems. In fact, this practice has only fallen out of favor since industrialization. Contrary to the notion of the faithful middle class man, polygamy was not restricted to the very powerful. It was only institutionalized for them. Men have been cheating as long as they have been marrying, and not just a little bit. Cheating is almost as common as marriage, historically.

If we compare anatomy and biology, we find this conclusion to be valid. There is a clear and virtually indisputable link between the size of the testicles and the fidelity of the species. Ours are not large enough for a thoroughly promiscuous lifestyle, like the chimpanzee's, nor are they as small as the most monogamous apes. Human males are not large enough, compared to females, to command harems in the same way as a gorilla. We are not antisocial enough to be as monogamous as gibbons. In all biological areas, we fall above the threshold of monogamy, and below that of outright polygamy.

If this conclusion leaves you feeling uncomfortable, try to keep that feeling at bay for a while. I promise this will make a lot more sense once we've examined the evolutionary developments that led us to this perilous double standard of demanding monogamy and practicing polygamy. If it helps you to understand the point, think about yourself for a minute, and your partner, if you are attached. If you are over the age of thirty, you've probably had between three and ten sexual partners, and most of them have been monogamous partners, though there's somewhere around a thirty or forty percent chance that you've cheated at least once in your life. Now, your partner has probably had around the same experience, and if you think about it, most of your friends have, too. Humans do not have sex monogamously today, and as we will see, they never have.

Game Theory and Mating Standards

Why would a species evolve into a particular mating pattern? Why aren't all species either polygamous or monogamous? In order to understand the answer to this question, we can think of evolution as game of strategy, with each side using whatever advantage it has, and trying to minimize its weaknesses. This is where game theory comes in.

Imagine a species that is polygamous. This means that the most powerful males have many females in a harem. If you are a male, you have two choices. You can either be one of the most powerful males in the group, or risk celibacy. No matter how dominance is chosen, the losing males find themselves without mates. This is not just conjecture. It has been thoroughly documented in nature. The more polygamous a species, the more the average male suffers. Only the most powerful get to pass on their genes. The rest literally die for eternity.

While this brutal male selection is going on, the females pretty much have everything they could ask, right? All of them get to mate, and they all get one of the crème de la crème as a husband. Well, in a sense, this is true, but there are disadvantages. For one thing, as the degree of polygamy increases, the amount of attention the male can devote to each female decreases. Though the offspring will be the children of royalty, they will have been raised essentially by a single parent. Furthermore, as the old adage goes, if everyone is special, nobody is. In other words, being the child of the king isn't particularly advantageous if everybody is a child of the king! In the next generation, each male will be on equal footing when competing for females. Since all the genetic material comes from the king, it's basically a matter of luck and the female's genes.

Eventually, this kind of system will reach a point of diminishing returns, where the females do not receive a significant benefit from mating with the most desirable male. When this happens, the most clever of the celibate males might figure out that he has an advantage. (Again, I am speaking very liberally about conscious decisions. This is for ease of understanding, and does not imply that evolution is intentionally doing anything.) If he devotes himself entirely to one female, and dotes constantly over the children, the female is actually gaining something by marrying down on the social ladder. As more and more females realize this advantage, monogamy creeps up on polygamy. It may eventually surpass it as the primary mating arrangement.

This works in reverse, of course. In a completely monogamous population, females are stuck with who they get. If only twenty out of one hundred males are attractive and strong, that means that eighty females are forced to mate with a dud. If strength correlates to resources, as it often does, clever females will eventually figure out that a half of a rich male is better than all of a poor male. Even with half of the parental attention, the benefit in resources is more than enough to make up the difference. If there is a mechanism by which males can accumulate vast resources, such as a large territory, or a particularly rich food source, polygamy will overtake monogamy.

As we might expect, complete monogamy is pretty rare in nature. Most animals fall somewhere in between strict monogamy and rampant polygamy, which is consistent with the theory that ecology and internal competition create a fluid and self-correcting system. Either system creates an inherent advantage for one gender or another, based on resources, population density, and many other factors.

So What About Humans?

Homo erectus was the most carnivorous monkey or ape ever. He represented a sharp divergence from the now extinct Australopithecus robustus, who lived almost exclusively on leaves, seeds, and fruits. Though it may pain some vegans to hear this, our entire society is very likely the result of our ancestors' love of raw meat. You see, in order to hunt meat, humans had to roam far from home. Unlike plants, prey animals do their best to get away – and stay away – from their predators. Not only that, but our pre-human ancestors were not nearly as fast as most of their prey. We gained much by standing on two legs, but we also lost much. For Homo erectus, the hunt required allies. Groups of men had to form social bonds, and then set out on the hunt, perhaps for days or even weeks at a time, until they were able to secure a large enough prize to bring home. Not only did man need social bonds, but he needed spears, for he lacked the claws and teeth of the other top predators. Both of these things require a big brain. As it turns out, this is the major difference between our extinct ancestors and ourselves. We were the only ones who figured out how to make tools, form groups, and kill big animals.

For over a million years, humans didn't evolve much. Our environment was stable, and we had achieved a stalemate with natural selection. We lived in small groups, formed pair bonds, experienced jealousy, lust, and emotional hurt. We were busy just trying to stay alive, and we hadn't discovered how to farm, so there was no way to build up enough resources to become highly polygamous. By all estimates, only the most elite males could be openly polygamous, and then, only with a small number of females. As for cheating, the jury is still out to some degree, but there is very strong circumstantial evidence suggesting that it was at least relatively common for all of our history.

Within the animal kingdom, there is a remarkably consistent tendency. The smarter the animal, the more flexible are its mating habits. We can see this very clearly in chimps and coyotes, two species that are very similar to humans in many societal ways. The degree of polygamy in both of these species changes slightly based on the availability of resources. With humans, we would expect that this tendency would apply, and as we progress in history, we will see that not only is this true, it is spectacularly true.

In a hunter-gatherer society, there is very little skill involved in staying alive. Either the food is there to pick, or it isn't. Either the herd is nearby, or it isn't. For this reason, there was no way for males to build up reserves, or to guarantee food in the future. The conclusion is clear. With no particularly powerful males, polygamy would never become the dominant mating model. However, things changed with the agricultural revolution. Once we figured out how to grow our own crops, our big brains kicked in at an astonishing rate.

As soon as one male accumulated more food than he and his mate and children could eat, he discovered the power of money. Obviously, he had no concept of the abstract currency we use today, but it was clear that he could use his excess food to buy the loyalty of his fellows. As labor goes, farming two fields is not significantly more difficult than farming one, especially with a little help. Soon, what was a slight excess of food became a large excess, which allowed the purchase of more loyalty. Man had discovered how to become rich. With this discovery, he changed the dynamic of mating by allowing females the option of choosing a portion of a very rich man over all of a very poor man. Polygamy was here, and it was not going anywhere for a long time.

In all of human history, pastoral societies have been polygamous, almost without exception. At the dawn of human 'civilization,' when we learned to build cities, kings and emperors and local rulers generally had thousands of women in harems. Kings had ultimate authority, and ultimate access to mates. In some South American nations, it was rare to find a child who was not royalty. Until as late as the 20^th century, many parts of the world were still operating within this model. Though it's not always pleasant for us to think about, the reality is that for virtually all of our history as agriculturalists, women have been monopolized by powerful men, leaving large swaths of the male population celibate.

Perhaps now is a good time to take a step back and try to look objectively at what we've learned. Please bear in mind that I am not suggesting how people ought to act, or how many wives a man should have. Also, please remember that, just like our taste for sugar, our drive to compete and our tendency to stratify our society is completely natural. Men are evolutionarily programmed to behave the way they do. It is incorrect to say that man became polygamous because of deficiency of morality, or because of a fault in his character. Simply put, the strategy that man discovered has been extraordinarily efficient. A population of a few million has become a population of six billion. This is no small feat, and as far as evolution is concerned, for a species as big as humans, it's nothing short of a roaring success. We're going to leave this topic for a while, but I promise you that later on, we will return to polygamy and discuss exactly what's wrong with it. In the meantime, we need to look at males and females separately.

Why Men are Lying Cheaters

In any species, sex is a competition. The females, with so much at stake, must choose their mates with great care, selecting the best male for genes, post-natal protection and childrearing duties. The males, on the other hand, have very little at stake genetically, and virtually nothing in time expended. (Women, feel free to make your 'minute-man' jokes at this point.) They literally have no compelling reason, in and of themselves, not to try to impregnate as many females as possible. With this notion as a starting point, let's examine human males, and see if we can discover just what it means to be a man.

The first thing we must know about males is that they tend to produce more children than females. This seems counterintuitive at first, but it's true. Men who marry twice are more likely to have children by both wives, and women are less likely to have children with their second husband. Add to this the fact that one particularly promiscuous male could have perhaps four or five wives in the course of a lifetime, all the while availing himself of the services of prostitutes and mistresses, and you will see the truth in it. Men produce more children than women.

If there's something twitching the back of your head about this, it's probably the question of how to work out the math if men produce more children than women. Obviously, there's a real number of children in the world, and it takes one man and one woman to make a child, so that can't be the way it is, can it? Yet, the numbers are astonishingly clear. Across all cultures, men who are fathers have more children than women who are mothers. It is undeniable. The only question is how we can interpret this information. What is the answer to this apparent paradox?

The answer is obvious, if painful. The only way for this to be possible is if virtually all females produce children, and many men do not. This is, as it turns out, completely true historically. There has always been a significant number of celibate men, usually the least powerful, or the poorest, or the ugliest. Furthermore, the ratio of men to women has always been essentially one to one. If for no other reason than this, we can say with certainty that humans are polygamous. (As we will see later, cuckoldry also plays a part in this odd equation, but not enough to explain the discrepancy completely.)

The next thing to know about men is that they must seduce women. Despite libraries full of feminist literature extolling the virtues of confident women asking men out, it remains the very rare exception to the rule. For all of human history, men have seduced women. This, too, lines up very neatly with other creatures who share similar mating patterns. In nature, the gender which spends the least amount of time in reproduction does the seducing. In the few species where males tend the young, or even more rare, carry them in their bodies, females do the courting, and males do the selecting.

Men are not entirely ignorant in their pursuit of sex. Overwhelmingly, we see a historical trend that is at least somewhat promising. Most men, having achieved a monogamous marriage, try very hard not to lose it. This doesn't mean that they don't cheat. It does mean that they usually go to great lengths to hide their indiscretions if they don't have the power to enforce polygamy. Most men, it seems, have a vested interest in maintaining something close to a monogamous relationship.

One of the most obvious traits males exhibit is their tendency to compete. Sport is ubiquitous, and until quite recently in our history, was virtually monopolized by men. Testosterone is clearly linked to aggression. Men compete for jobs, for money, for land, for possessions, for women, and pretty much anything else of value. This drive to compete is a direct result of female selection. That is to say, because females choose the best males (whatever the criteria might be), the males must compete so that the female can choose properly. It's a cruel twist of fate that the 'right to choose' inherent in females is what led to the complete domination of females by men after the agricultural revolution. Once men learned how to become rich, they learned how to become kings. It was only a short jump in logic to realize that kings (the winners) could have as many mates as they wanted. In all six of the early civilizations – Babylon, Egypt, India, China, Aztec, and Inca, one man ruled with complete authority, and had rights to virtually any females he wanted. There are records of some rulers complaining of their regimens, as many kings were literally obliged to perform sexually at least two times a day every day with different concubines. In all of these civilizations, there were elaborate records noting exactly when each concubine would be the most fertile. Clearly, to males, sex is something to be fought for and won.

What is more notable than the behavior of kings is the observation that kings were not special in kind – only degree. Across all of these cultures, men with power had harems of proportionate size. As wealth diminished, so too did the quality and exclusivity of the harem, but the desires and goals of men are clear. Even among the lowest level of landowners, there was rampant polygamy. The Roman Empire is a perfect example of this. Though marriage was between one man and one woman, we can learn a lot from the slave trade. Most of the actual labor was done by male slaves, for obvious reasons, yet young female slaves brought the highest price on the open market. Not only that, relatively small houses were often filled with an inordinately high number of female domestic servants, who were, by and large, all young. More convincingly, Roman nobles freed many of their slaves at remarkably young ages, leaving them large inheritances. The common thread? All of them appear to have been children of slaves. Why else would they be freed, except that they were illegitimate offspring?

Though we think of Christian Europe as a monogamous place, it's just not true. Polygamous mating was kept more secret, but it was no less prevalent. The countryside was male dominated, leaving many men celibate, primarily because castles and monasteries employed huge numbers of serving maids. In some cases, contemporary historians explicitly mention “gynoeciums,” where the secret harems of castle owners lived. Add to this the fact that among men with one wife and no servants, there is no indication whatsoever that cheating was any less common when there was an opportunity for it.

The last thing that we must realize about men is that they are violent, and that their violence has a lot to do with sex. It has been convincingly demonstrated that war among humans did not originate over resources, but mates. All studies of preliterate societies reveal very high levels of violence between men, with the inevitable result being the capture and sexual conquest of the females. In earlier historical periods, rape was one of the most attractive incentives used to recruit soldiers. Even today, rape is not uncommon in war, and shore leave is at best a thinly veiled excuse for soldiers to buy the services of prostitutes.

To quote Matt Ridley, to whom this essay is unquestionably indebted, “The nature of the human male, then, is to take opportunities, if they are granted him, for polygamous mating and to use wealth, power, and violence as means to sexual ends in the competition with other men – though usually not at the expense of sacrificing a secure monogamous relationship.” (The Red Queen, 206) As we will see in a moment, human sexual competition is not one sided. Females have their own games to play, and their own motivations. Clearly, the domination of rampant polygamy is at an end, for when we look around the world today, we see that even the most powerful men must now at least make a good show of discretion with their mistresses. Although cheating is still very common, and multiple marriages are the norm, there has obviously been some dynamic that has caused a shift in the balance of power. Men don't get everything they want, no matter how powerful. We must explore the nature of females to discover what has caused this.

It appears that rampant polygamy is not the norm for humans. The last four thousand years or so, it has been rampant, but it gives every indication of being a blip on the radar, in between hunting and gathering, and democracy. With democracy, we have seen the redistribution of power. Though there are precious few despots left in the world, there are still vast gaps in between classes. Even so, it appears that the gaps are not wide enough to make open polygamy the norm. As before, humans appear to be settling into a slightly uncomfortable stalemate of almost monogamy. Indeed, when we examine the habits of our closest animal analogs, we discover that the most likely norm for human behavior is monogamous marriage with rampant and very secret cheating by both males and females.

In some ways, it's a good thing. The one constant among polygamous societies is that they are drastically more violent than monogamous societies. Because of the intense competition among men to be one of the lucky few who gets to mate, instability and violent infighting are the inevitable result. Ironically, as we will discover momentarily, women's tendency to cheat has had a tempering effect on men, forcing them into monogamous societies, while allowing them to engage in extramarital affairs. In a very odd way, both men and women get to have their cake and eat it, too.

Why Don't Women Bear Their Husband's Children?

We've pretty firmly established that men are scum, right? All they want to do is have sex with as many women as they can, and the only thing stopping them is their own level of power, right? Well, not exactly. This picture is entirely one-sided, and doesn't account for the fact that through most of human history, women have been able to enforce near-monogamy on men. How did they do that, exactly? Moreover, is it fair to say that women have been nothing but the pawns of men for all of history? Are they little more than incubators for male genes to be passed through?

It's easy to understand why women often describe history as an entirely male dominated story. It's also easy to understand that women are often frustrated by the apparent paradox. If women have so much power as the selectors, why do they always end up on the short end of the bargain? When the men leave, women are the ones left holding the baby and all the responsibility, and the men get to go out and make more babies, with little or no consequence to themselves. For all the power women are supposed to have, they still can't seem to get paid as much as men, and they've had to fight tooth and nail for everything they've ever gotten. You never hear about men being left at the altar, do you? Women just want a man who will be faithful, and then they'll be happy, right? If only men would be faithful, everything would be perfect.

As it turns out, there really is a paradox that explains how women impose monogamy on men, and it fits perfectly with the ever-growing body of evidence that suggests that nearly everything we think of as being “above nature” about humans is actually evidence that we are unavoidably tied to our animal roots. Here, then, is the answer to why men marry, and why they prefer long term relationships with one woman. Women cheat. Often.

One of the most dramatic advantages, genetically, of being female is that there is never any doubt of parentage. In other words, a mother knows with 100% certainty that her child is her own. (This, of course, doesn't take into account modern medical procedures, but you get the point.) Since evolution is not concerned with ethics, only successful reproduction, it stands to reason that females would have learned to take advantage of this fact. They clearly have. Though the numbers vary slightly depending on the particular culture, one thing has been proven rather conclusively. In cultures that are primarily or strictly monogamous, cuckoldry is common. In the landmark study, conducted in Liverpool in the 1980s, it was discovered that less than 80% of children were actually related to the man who believed himself to be the father.

If it is true that human nature is the cause of this phenomenon, we ought to see biological evidence. It so happens that the evidence is striking. Recent investigations of the female orgasm have given us a rather shocking dose of reality. It has long been known that there are some female orgasms that cause more sperm to be retained after sex. These are called high-retention orgasms. Obviously, high retention orgasms have a higher probability of inducing pregnancy. What was shocking to researchers was when they examined orgasms alongside fidelity. In faithful wives, approximately 55 percent of their orgasms were high-retention. However, among unfaithful wives, only 40 percent of their orgasms with their husbands were. Even more shocking, though, was the fact that over 70 percent of the orgasms with their adulterous lovers were high-retention. There is more. Without consciously being aware of their most fertile period, women tend to have sex with their lovers on their most fertile days.

The combination of these numbers is shocking. Though women tended to have sex with their husbands twice as much as their lovers, they were slightly more likely to conceive with their lover than with their husband. It appears that women have a biological drive to keep their husband while bearing the child of another man. Again, if this is true, we should be able to make predictions based on other animals who behave similarly. Again, we can.

In a previous essay, I noted that human females are rare in comparison to the rest of the animal kingdom. Rather than having a small window of sexual availability and interest, they are sexually active essentially all the time, but only fertile a small percentage of that time. Another aspect of this system is that fertility is concealed. Except in very recent years, there has never been an accurate measure of peak fertility. One immediately apparent advantage to the female is that this system allows her to choose her mates much more selectively. If, like other animals, human females displayed fertility with a clear physical sign, and were only receptive to sex during this period, men would only be interested during these few days, and culture would be much, much different. As it is, women have as many days as they want to choose between as many potential suitors as they desire.

There is an odd side effect of concealed ovulation. Since ovulation is concealed, adultery becomes easier, for on any given day, the woman can leave in secret to have sex with her lover, and her husband, ignorant of her fertility, is none the wiser. As we have seen, whether they know it or not, women are instinctively aware of this fact, and use it to their advantage when they do have affairs.

Why would female cheating have such a profound effect on men? After all, men are supposed to be interested in having sex with as many women as possible. Why would female cheating be such a threat? Like other polygamous animals, humans produce 'smart sperm.' Some sperm avoids trying to get to the egg, instead forming a kind of blockage that prevents other sperm from getting in. Other sperm are literally attack sperm, actively trying to destroy sperm from competing males. All of this is a testament to the fact that even on a cellular level, men really don't want other men having sex with their women. The math is clear. If many men have sex with a woman, the chance of any one man being the father is dependent on how many men there were. On the other hand, if a man can keep his woman faithful only to him, there is a 100 percent chance that he is the father. It almost goes without saying that virtually all the laws in history regarding adultery have been geared towards punishing women for having more than one man. Our biology predicts this.

There is a clear pattern in nature. In species that have rampant adultery, particularly birds, interest in frequent sex is almost always observed. Birds turn out to be the closest analog to humans, sexually. Like many species of birds, humans live in colonies. Swallows, in fact, are very close to humans in their sexual practice. Consider this. In swallows, 'married' females often have affairs with dominant older males, but they do it in secret. When a male has been cosmetically altered by researchers to be more attractive, his chances of having an adulterous affair doubles. The more attractive the male is, the more chance he has of being a deadbeat dad. Husbands are very jealous of their wives and often follow them around anytime they leave the nest. Anytime the female leaves for an extended period, the male becomes adamant about having numerous sexual encounters with her. One of the most disturbing things that we've seen in swallows has only been discovered recently. Until genetic tests verified that cheating is rampant, scientists thought swallows were pretty much completely monogamous. The reason they thought this? Swallows are very good at keeping their adultery secret!

Is any of that making you twitch a little? There's more. The research on swallows, unhindered by the objections of the church or feminists, has proven rather conclusively what the female's reproductive strategy is. Marry the male who will remain faithful, and reproduce with the one who will produce the best children. Does this sound like a cynical view of human marriage? If the facts line up, why would we use the word 'cynical'? It turns out that when we examine human society, across cultures, women have a propensity for carrying on secret affairs with one man who is usually an 'upgrade' from her husband. Depressing? Perhaps, but it is true.

Males have adapted to combat this tendency. Men whose wives have been gone all day produce much more sperm than those who have been with their wives all day. Consider the adage, 'Absence makes the heart grow fonder.' As it turns out, it also makes the testicles more fecund. The same thing happens in rats, incidentally. Once again, human behavior lines up with animal behavior. What we think of as intellectual, or cultural constructs, are actually deep rooted instinctual behaviors. We cannot control them on a biological level. They simply exist. It would be foolish of us to deny this fact.

Jealousy is one of those mythologized concepts that we seem to have a very hard time understanding. Despite voluminous research indicating that lack of jealousy is a near-perfect indicator of impending divorce, we insist that jealousy is something to be suppressed or avoided. It is seen as an aberrant behavior. In reality, it is one of the mechanisms that keep both men and women relatively monogamous. Without jealousy, we can imagine that both men and women, with their innate tendency to cheat, would eventually throw off the yoke of monogamy and live in openly polygamous communes. They do not, and every attempt at creating such a commune has utterly failed.

Once we take the labels “good” and “bad” off of human behavior, we can begin to see a cause and effect chain. Once we recognize why we are the way we are, we can begin to evaluate our own feelings based on our own goals. If we try to do it the other way around, we are dooming ourselves to failure. Human nature is neither good nor bad. It just is. Individual goals, on the other hand, can be good or bad, based on what outcome is desired. For a man who has had a vasectomy, the reproductive goal is clearly gone, but the motivations and desires still exist. Only by a clear understanding of why he feels the way he does can a man begin to decide with rationality what his behavior ought to be.

In short, here's how it works. Men would like to have as many women as possible, but in egalitarian systems, this is rarely possible. Women would like one man because of his contribution to childrearing. Women are also restricted by outside realities. They seldom get to marry the best man available, not to mention the fact that the most reproductively viable man is seldom the best potential husband. To this end, women often engage in extramarital affairs with one man, usually an older, richer man, and more often than not, married. Men, aware of this propensity in women, become jealous of their women and guard them relentlessly. They also attempt to reduce the chance of being cuckolded by having sex with their wives as often as possible after being separated. Married men are also, ironically, pursued as potential lovers by women with lesser husbands.

The bare truth is perhaps not as rosy as we'd like, but it's also extremely parsimonious in explaining why we act the way we do. Men and women both cheat, and always have. Marriage in humans is a tenuous balance between drives. Women instinctively want to keep their men for financial and childrearing advantages, but they have a natural drive to trade up in secret if they get the chance. Men, likewise, have a natural drive to be the one selected for an upgrade, which conveniently allows them to engage in their biological drive to be polygamous. It is not a pretty system if you believe in Christian morality, but if you think about the reality of the marriages you've seen, or your own experience, it is a very elegant explanation for what seems to be contradictory desires in our own nature.

To avoid excessive length, I'm going to mention some other real, scientifically verifiable aspects of human sexuality, without going into the research or the comparisons with other similar animals. There are plenty of books available on any of these subjects, and a trip to the local university library would give a reader years worth of material, if he truly desired to delve that deeply into the subject.

Beauty matters. Men all over the world are most attracted to women who are post-pubescent but who have not had children. Beauty is most accurately described as incredibly average. That is to say, we don't like abnormally large or small features. Interestingly, across the world, the photos that are universally perceived as most attractive are actually composites of many faces. It's not about weight as much as waist to hip ratio. Small waists compared to the hips are attractive.

Humans instinctively know what their mating potential is. They tend to try to find the best among their available pool. In other words, ugly women tend to marry men who cannot attract beautiful women. It's not politically correct, but it's universally true. Men are much more interested in beauty than women. Women are much more interested in wealth and power in a mate. Sexy men do make poor husbands, on average. Men lie to their wives about having mistresses, but they are generally honest with their mistresses about their wives.

What Does It All Mean?

Finally, we must put all of this in perspective. This is perhaps the most crucial element of this essay. All of these facts about human nature are trends and averages. They do not speak to any one person's desires or tendencies. You may want to object that you have had a vastly different experience, but this cannot be an objection, since none of these trends can be used to accurately predict an individual's behavior. As I have said many times before, humans are incredibly diverse, and deviance is something that is part of our nature.

However, it is also impossible to deny these trends as inherent, innate, instinctual realities. Though our own lives may have been shaped by our experiences, and we may not fall under these broad generalizations, they are nonetheless valid. Regardless of what you have become as an adult, you were shaped by your inherent sexual nature.

Now, we must recall the lesson of sugar cravings from a previous essay. We learned why we crave sugar, and we learned that immoderate consumption of raw sugar can lead to dire consequences – not least of which the lessening of our own sexual attractiveness, which does matter. We learned that it is quite possible to begin to put together a system of ethics about sugar consumption, based on the scientific evidence of what consequences follow from different consumption patterns. If we wish to be sexually attractive, healthy, and long-lived, we can certainly eat sugar, but we must be careful of processed sugar, and we must engage in enough exercise to burn off any excess calories we might consume.

Can we apply the same mentality to sexuality? I hope you're beginning to see that we can. We're not quite ready to make any broad statements, because there are aspects of sexuality that we have not covered, such as sexually transmitted diseases, emotional consequences of various sexual activities, and the physical consequences of various types, or levels of sexual activity. Nevertheless, we ought to be able to form some rather firm objective statements about ourselves and our culture. For instance, marriage is something that reflects human nature, but it does not reflect all of it. Both men and women desire and engage in extramarital affairs. Many couples successfully practice 'open marriages.' Pockets of polygamy persist. Very rich men move to South America and buy the services of young housemaids. The tendency to get tired of a mate after childbearing is natural. The male desire for young women is natural.

In short, what we have learned so far is that much of what we consider immoral or unnatural in humans is not only natural, but essential in building the mating system that we have now.  Humans desire long term relationships with one person, but there is no particular indication that humans are supposed to mate for life, especially since life has been extended to over seventy years. If divorce is available, and a relationship has failed, there is no natural reason to continue in it, for humans are built to move on to another mate. In fact, we're designed to desire just that! If there are other reasons to stay together, such as financial or legal reasons, we can judge them as they come, and decide what's best. Like sugar consumption, we can look at marriage and mating as the results of natural instincts, which will, with any luck, allow us to judge cause and effect more objectively, without the baggage from religion and myth which tell us that our sexuality is evil or depraved or out of control.