Why Monogamy Is A Myth

When it comes to sexuality, many people believe that humans are unique in the animal kingdom: we feel love, we’re psychologically complex, we form long-term monogamous bonds.

Well, science calls shenanigans on our idealism.

According to scientists, the similarities we find between animals and humans actually reveal some of our most basic instincts, and monogamy isn’t necessarily one of them. Take a look at these five animal behaviors with uncanny parallels to humankind:

1. Males are naturally polygamous, while females are naturally monogamous

This first tidbit of insight is drawn from a study by sociobiologist Robert Trivers, in his seminal work titled, “Duh.”

Natural selection is based on the principle that parents pass on their traits to their offspring. Any heritable traits that enable an individual to produce stronger or more offspring will spread from generation to generation with greater frequency, while those that result in weaker or fewer offspring will gradually be extinguished.

Instinctively then, animals behave in such a way as to maximize their chances of producing offspring, because these are the behaviors that get passed on. That tingling sensation we feel in our nether regions when we see an attractive member of the opposite sex? It’s just our body’s way of prodding us to procreate.

He’s only doing this to get laid

Actually maximizing one’s reproductive success, though, can be a vastly different task for the males versus the females of a species. It boils down to the level of investment each sex puts into the mating process. For most animals, the female investment may last several years: thirty minutes of sex, several months of pregnancy, and years of parental care. The male investment, on the other hand, rarely lasts more than an hour: one pickup line, six or seven drinks for her, two minutes of sex, and a mental high-five to oneself.

Trivers noticed that throughout the animal kingdom, the sex that invests the least in reproduction tends to strive for quantity of matings, while the sex that invests the most in reproduction tends to strive for quality of matings. That is, the male is effectively just a sperm donor, so he increases his reproductive success by engaging in as many matings as he can secure. The female, on the other hand, gets stuck raising the baby, so she increases her own reproductive success by mating only with the strongest male, who will then provide her with the strongest offspring.

Okay, so there is one exception to the female investment rule

In other words, males instinctively want to mate with every female out there, while females are instinctively choosy about their mates.

Um, yeah. Did you really need to be told that? Still, it gets more complicated….

2. Females are drawn to wealth, power, and aggression

Since males instinctively try to mate with as many females as they can, the competition between males can be fierce. In countless species of mammals and birds, males compete against each other to acquire the best territories. Or they will fight to show off their gaudiest assets, strutting around flashing their feathers, antlers, or whatever animal bling they have at their disposal.

Case in point

This competition between males can end in one of two ways: One male physically drives away all the others and therefore has unfettered access to all the females in the population. Or, the males each display their best seduction routine, and the females survey their options and choose to mate with the one male they each deem the most worthy.

Either way, guys, this is why your girlfriend dumped your wimpy Geo-driving ass for that burly hulk of a man with the shiny new Beemer. Women are drawn to men their primal instincts believe will either provide the necessary resources to raise their kids, or possess the strongest traits to pass on to said kids. The dudes with the money and the power are the ones who get the chicks. File this again under “Astute Observations By Captain Obvious.”

What may not be so obvious is that females also indirectly select for aggression in males. Since competition between males is fierce, the aggressive male is able to secure more matings and, hence, spread his aggressive genes. At the same time, the timid male will secure few matings, so his timid genes will not get passed on. Over time, males will thus become more and more aggressive.

It’s what the ladies want

In essence, women are attracted not only to wealth and power, but also to dominance and aggression.

Well, crap. Maybe this one is pretty dang obvious, too. Okay, try this now….

3. Monogamy develops as a way for unattractive males to find mates

One result of male competition is that the most dominant male often secures the vast majority of the matings. In fact, the dominant male in some bird species may engage in every single mating during one breeding season, forcing all the other males to plod back to their nests in dejection and turn to the internet for some hot boobie action.

This kind of boobie, of course. What did you think I meant?

Similarly, the history of human society is peckered… er, peppered with stories of the harems that powerful men controlled. From Roman emperors to Inca kings, men of power and wealth have always commanded access to hundreds, if not thousands, of women.

Insert obvious joke here

So what is the weak male to do then? In his never-ending quest to score some feathery tail, the non-dominant male has stumbled upon a tolerable compromise: He offers parental care to the female, something she won’t get if she joins the dominant male’s harem.

In lark buntings (no, seriously, that is the actual name of a real bird… just like “cock” and “tit” and “boobie”), the dominant male provides nothing for the females other than his territory. After mating, she builds the nest, broods her eggs, forages for food, and raises the young all on her own. If the swath of land the dominant male commands is rich enough in resources, females will gladly accept this arrangement.

At some point, though, the dominant male stretches his resources too thin. Once he reaches a certain number of mates, then it’s no longer in a young female’s best interest to join the dominant male’s harem. At this point, the female is better off finding a non-dominant male who will stick by her side and help her raise her young.

This exact phenomenon occurred in pre-communist China, where rich men frequently took two or more wives. In those days, a woman from a poor family faced the decision of becoming the fourth wife of a rich man or the first wife of a poor man. If the man was rich enough, she chose to become the fourth wife. If not, she took her chances with the poor, unmarried man.

For the non-dominant male then, his options are pretty simple: offer to stick with one singular mate and help her raise her young, or not find any mates at all. In short, the non-dominant male offers monogamy because he is unable to attain polygamy.

Give him a chance, ladies. He’s offering you monogamy!

4. Females find attentive husbands, then cheat on them with attractive males

But wait, we’re not done with the freakish bird sex. Even among species that form monogamous pair bonds, attractive males make inattentive husbands. As Nancy Burley discovered with zebra finches, while Anders Moller discovered with swallows, the males who are able to attract the most females also put in the least amount of work helping to raise their young. On the other hand, unattractive males tend to be noticeably hard-working fathers. They help their mates build the nest and find food, and they work hard to raise their young.

That’s right, hunky and attentive are mutually exclusive male qualities in the animal kingdom. If both hard science and popular science say so, you know it must be true.

The Myth of Man

The female’s dilemma can be summarized thusly:

If she mates with an attractive male, she will likely have attractive kids. However, she will have to work harder to raise her children, so they may not grow up to be as healthy or as strong. On the other hand, if she mates with an unattractive male, he will be there to help feed and take care of her children. However, her offspring will not grow up to be particularly attractive.

Of course, females, in their infinite shrewdness, have devised their own solution: They find attentive mates and cheat on them with attractive males.

Apparently, birds can be quite the connivers, engaging in the ultimate euphemism known as “extra-pair matings” (that is, matings outside of one’s pair bond). In fact, adultery abounds in the supposedly monogamous world of bird couplings. Females frequently form pair bonds with unattractive, but attentive males, then engage in extra-pair matings with attractive males when their mates are off foraging for food and nesting materials.

Biologist and author Matt Ridley argues that the reason women stray from their marriages is simply a holdover from our primitive hunting-and-gathering days. In the same way a man acts according to his reproductive self-interest, a woman acts in her own self-interest by finding a husband who will be a good caretaker of her children, but then mating with a strong, attractive man in order to produce strong, attractive children. It’s a cruel world out there.

Yes, ladies. You can have this and eat it, too.

5. Even when monogamy develops, it’s only temporary

Well, then. Now that we’ve gotten this far, let’s go ahead and hammer that last nail into monogamy’s coffin, why don’t we?

As it turns out, we can reasonably expect a human female to squeeze something the size of a grapefruit out from between her legs, but we can’t expect her to do the same with something the size of a bowling ball. As human brain size increased over millions of years, women had to give birth earlier and earlier during pregnancy. Compared to most other mammals, humans are born much earlier in their physical development. Any later, and there’s no way that infant’s head is fitting through mom’s birth canal.

Pretty much this

This means that human infants require a much longer period of care before they are able to fend for themselves. In turn, this means that human females benefit much more from a two-parent system than any other animal. A male who assists his mate therefore increases his likelihood of producing viable offspring. Humans are more monogamous than most other animals, after all. In fact, the human mating system is probably most similar to birds, since baby birds also require a great deal of parental care (hence, all the bird examples here).

Of course, there’s still a catch: monogamous pair bonds only last as long as necessary to raise the offspring past infancy. Once the young are able to fend for themselves, the male and the female usually separate to find new mates. In the animal kingdom, lifelong monogamy simply doesn’t exist. Even species previously thought to be permanently monogamous are turning out to be only serially monogamous.

In its truest form, permanent monogamy only exists in angler fish, wherein the male attaches himself to the female and lives parasitically off of her for the rest of his life. He gets food, lodging, and sex. She gets sperm. That’s right, true monogamy in the animal kingdom can be reduced to the aquatic equivalent of the deadbeat boyfriend.

The deadbeat boyfriend of the sea

Social anthropologist Helen Fisher has argued that divorce rates spike at the fourth year of marriage because that’s around the time that a human infant no longer needs care from two parents. As such, the fourth year is when humans begin to break their monogamous pair bonds and instinctively seek out new mates.

Thus, even when we embrace monogamy, we’re only temporary, serial monogamists at best. How’s that for instilling faith in human traditions?

So what does this all mean for us?

When it comes to failed relationships, one of the most common explanations we hear is, “it just didn’t feel right.”

Fair enough. If a relationship doesn’t feel right in our gut, that may be cause for concern. But here’s the problem: As the examples from the animal kingdom and from human history show, monogamy will never “feel” right. Our instincts will continually drive us to form temporary monogamous bonds, but still cheat on the side. That’s how we maximize our reproductive success. That’s the legacy of human evolution.

So maybe, there has to be more to human relationships than just something “feeling right.” Maybe, instead of following our gut like… well, like animals, we should follow our head a little more. You know, the part of us responsible for higher reasoning, like logic, ethics, morality, and the ability to play Minesweeper.

Because that’s the part of us that makes committed, monogamous relationships possible.

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By day, I'm a marriage and family therapist. By night, I am a relationships and comedy writer, which can be redundant or an oxymoron, depending on your perspective. I'm the creator of Social Savvy Sage, a coaching service that focuses on developing social skills. I am also the creator of Musings, the blog you're reading right now. You can find me on Twitter. (I am not the creator of Twitter.)


  • Stumbling upon this through cracked.com, I found it to be exactly what I needed to hear at this point in my life. However people do exist who don’t have such a high sex drive as considered normal or they are asexual and not attracted to females or males. Why would they exist if sex drive is only a desire to reproduce? Likewise why would people be attracted to the same sex if such a pair can produce no offspring? Just food for thought 🙂

  • So women get what they biologically desire from aggressive mates.

  • What a crock of bull. Maybe for the weak minded ill educated rodents that call themselves human this applies.

    However, my parents have educations and have been together for 30 years with NO affairs. My aunt, educated, and her husband, a major businessman, have been together for 54 years. My other aunt has been married since high school, a little over 60 years, to the same man and they, are not educated per say, but they got more value in their pinkie fingers than 90% of the trash in society nowadays.

    What it comes down to is a few things:

    1) women are sluts. And this is coming from a 27 year old woman. The shit I see females pull nowadays makes me disgusted to be of the same sex.

    2) they like don’t males because by and large the females have little in the upper story. I mean the number of dumb cows I see walk into walls & doors at the local university is pathetic while texting on their phones. You’re not going to die.

    Your comment about women screw attractive men then raise the bastards as if the “ugly” guy’s kids shows you’re not in touch with reality. The dumb slut will be out on the street faster than you can say whore when the “ugly guy” realizes that those aren’t his kids.

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