Article By Dr Kate Lister
According to the dating app Feeld, there has been a dramatic surge of interest in couples opening up their relationships and exploring non-monogamy. Since the last lockdown was lifted, the app has seen close to a 400 percent increase among women keyword searching for “ethical non-monogamy” and “polyamory” – a whopping 500 percent more than this time last year. Given the obvious interest in non-monogamy, you have to wonder, when did monogamy become the norm? Are we even supposed to be monogamous?
If we are, then humans are part of a very select group of creatures. True monogamy in the animal kingdom is incredibly rare, especially in mammals. The California mouse and the Malagasy giant jumping rat are among just a handful of animals that have ever been identified who really do mate for life and stay faithful to one another. Scientists call this kind of monogamy “genetic monogamy”.
There are animals that are almost completely monogamous; prairie voles, swift foxes, golden-cheeked gibbons, who all try their best not to stray but don’t always manage to stay faithful.
Despite what Friends merchandise has told us over the years, lobsters do not mate for life. In fact, they’re quite slutty. They form a monogamous attachment, or a “pair bond”, for about a week, shag each other senseless, and then part ways. It’s more of a holiday romance than an exemplar of eternal love and devotion. This type of monogamy, where an attachment is formed and both partners are faithful-ish for the duration, is known as “social monogamy” and is pretty common throughout the animal kingdom.
And what of humans? We’ve all been raised on a diet of Disney movies and love ballads that seem to promote genetic monogamy, not only as the norm, but as aspirational. This might be true for a lucky few, but I think we all know that, as a species, humans are not strictly monogamous. Truth be told, we aren’t even monogam-ish.
At best, we trying to stay faithful to one partner at a time (known as serial monogamy) but even then we’re not great at it. A 2019 literature review on human mating patterns concluded that, “while there are many ethnographic examples of variation across human societies in terms of marriage patterns, extramarital affairs, the stability of relationships, and the ways in which fathers invest, the pair-bond is a ubiquitous feature of human mating relationships.”
Which means we are socially monogamous: forming primary partnerships, one at a time, and really, really trying not to shag other people. Basically, we give it a go.
So the question then becomes, why do we keep trying to “pair bond” and stay sexually faithful to one person? Where did this model come from, what function does it serve, and why do we keep trying to do it?
Monogamy is actually something of a conundrum to anthropologists. From a purely evolutionary point of view, it doesn’t make much sense. I’m sure you have heard as many variations on “men are supposed to spread their seed”arguments as I have, but what is often overlooked, is that women are supposed to do this too.
Having as much sex as possible will increase the chances of falling pregnant enormously and having sex with multiple partners means sampling a wide range of genetic goodies. It’s even been suggested that the reason human sperm coagulates after ejaculation is to help block rival sperm from gaining entry to the cervix. Simply put, your swimmers are expecting a crowd. Lots of non-monogamous animals do this. It’s called a “mating plug” and if you want to ruin your afternoon, do look this up online.
Yet monogamy overrides all of this and can actually leave you circling the shallow end of the gene pool and there is, as yet, no satisfactory explanation as to why humans do it. But there are a lot of theories.
There is certainly a historical influence to consider. It can be tempting to think of our earliest ancestors cavorting in sexual abandon with multiple partners in an Edenic paradise – but that is far from certain, and if you make such claims at an anthropology convention, prepare for a fight. “Pair bonding” with one primary mate is found in almost every culture throughout history – it is often referred to as “marriage”.
But marriage and monogamy are not the same thing and never have been. Throughout the ancient world, men were expected to take a wife but have sexual relationships outside of that with slaves, concubines, hareems, mistresses, etc. This is a system known as ‘polygyny’. Women having multiple husbands and male lovers (polyandry) is much, much rarer, but not without precedent. Fraternal polyandry is still practiced among some Tibetans in Nepal, for example.
The Catholic church didn’t think too much of polygyny and St Augustine tried to abolish it in 380ACE and in 534 ACE, the Justinian Code criminalized extramarital sex. But this didn’t stop people from playing away, it just pushed the idea it was a sin, and not everyone agreed. European monarchs were not only expected to take a mistress, but the role of royal mistress was an official title at court. It was an aspirational job. In fact, the pressure to have a mistress was so great that Frederick I of Prussia (1657-1713), who was deeply in love with his wife, appointed Catharina von Wartenberg (1674-1734) to the role, but never actually had sex with her.
Monogamy has been held up as the norm in Western culture for thousands of years and there is some truth to the argument that we keep doing it because we have inherited it, but this doesn’t satisfy evolutionary biologists, who have their own theories about why we keep trying (and failing) at sexual fidelity.
One of the most accepted theories is that of paternal care and joint child-rearing. Human (heterosexual) mating patterns throughout history have been largely driven by who is left holding the baby. Human babies need constant care if they are to survive, which means someone has to look after them. Pair bonding makes this considerably easier because resources can be shared which, in turn, improves the offspring’s chances of survival. Arguably, bonding with more than one would be even better, but one partner, at least, ensures co-parenting can take place. Even couples who have no intention of having a baby are still hardwired to be exclusive.
And then there is money. Money has a habit of changing things and the rise of capitalism certainly changed how we had sex. As soon as we started passing money and titles down the male line, making sure your missus didn’t have someone else’s bun in her oven became paramount. This theory not only plays out in most of western history but it helps explain why polygyny is so much more socially acceptable than polyandry. The Sultans of the Ottoman empire, for example, enjoyed a harem of several thousand women who, in turn, had to remain entirely faithful to their lord or risk being put to death.
If you don’t have 15,000 concubines to be getting on with, then pair bonding with one person is also a good idea if there aren’t enough sexual partners to go round and it has been posited that population density and availability of mates may also have played a part.
It has also been suggested that humans are monogamish because of “concealed ovulation”, which means there isn’t any obvious sign when it’s optimal baby making time. Meanwhile, when a female baboon is in the mood, her hindquarters swell up like a lifebuoy ring to let everyone know.
Another theory on human monogamy is “sexual dimorphism”, which basically means the difference in size between males and females. In primates, the bigger the difference, the less likely they are to be monogamous. Male gorillas, for example, are almost twice the size of the females and he will compete fiercely to maintain exclusive sexual access to his hairy hareem. Chimpanzees, on the other hand (our closest genetic relative), are significantly closer in size and tend to be monogamous and polygynous.
There may be some historical evidence to back this up. Scientists believe that once upon a time, dimorphism was more prominent in humans. By once upon a time, I mean roughly 4 million years ago when australopithecines were getting jiggy. The theory goes dimorphism decreased as monogamy increased. But this is contested as finding enough remains to prove this beyond doubt is tricky.
My personal favorite theory is that of testes size. It is a fact that in species where females mate with multiple males, the testes tend to be larger in relation to body size. This is an argument explored in Ryan Schacht and Karen Kramer’s 2019 paper, where they conclude, “adjusting for body size, human testes are smaller than would be predicted, and, when compared to our closest living relatives, are considerably smaller than those of chimpanzees. Together this provides evidence of relatively low rates of sex outside of a pair-bond”. So, there you have it. Men just don’t have the balls to be properly promiscuous. Science says so.
But, as a species, we are not completely faithful and never have been. Not that any of this will get you off the hook should you stray from the marital bed. You can explain about the tiny testes and sexual dimorphism, but I doubt it will do any good.
If you are someone who married the first person you ever had sex with, and you were their first lover too, and if you have both stayed completely faithful to one another and never even thought about being with another person, please report to the Royal Anthropological Society, along with the California mouse, and the Malagasy giant jumping rat, immediately. You are a very special monkey indeed.
A version of this article originally appeared here on inews.co.uk