The Monogamy Myth: Is fidelity as natural as we’d like to think?

It’s the late 1940’s in Middle America, and an acclaimed geneticist is settling down in his office ready to add proof to the theory that a person’s blood group is directly inherited from their parents. The theory is simple to him – the molecules that make up the baby’s blood group will be a mix of molecules from both their mothers and fathers blood groups. He’s put in the work, going to a local US hospital and collecting blood samples from over 1000 new born babies and their parents. And now he’s ready to use genetic reasoning to confirm what he already knows.

But his results are not adding up.

Almost ten percent of the children in his study had at least one molecule that was not found in either the mother or the father. There was no way his theory was incorrect. The science was sound. The only possible reason for this was one that he had not mentally prepared himself for.


One in ten of the children he sampled were the product of adultery.


With that realisation, the researcher quickly wrapped up his study, refused to publish the results and distanced himself as far away from his findings as possible. In fact, it was so scandalous for the time that the researcher went to great measures to remain anonymous and keep the results hidden, just in case it might taint his previous work. To this day we have no idea who that researcher was, and it wasn’t until the mid-nineties that his findings were even revealed, thanks to some digging from scientist and author Jared Diamond.

You might be thinking to yourself how this was likely a one off? It was the forties, surely that area just had a bunch of overly bored housewives, right? Of course today’s different?

I hate to break it to you, but since then several studies have proven similar results. Current research suggests that 2-3% of all children are the result of an affair, while a 2006 study claimed that 19% of men and 13% of women married under the age of thirty had cheated on their partner. And those are just the ones that admitted it.

As a society that holds monogamy as the highest and most romantic form of relationship structure, a lot of people seem to be digressing, leading several researchers to ask the hard questions – Is monogamy not as natural as we once thought? And is infidelity more natural than we would like to think?


So how do our animal friends feel about playing away from home?




Well it seems like a whole lot of them don’t really care. Out of the roughly 5000 known mammals, only 3-5% are known to form life-long pair bonds, including otters, beavers, wolves, foxes and a few species of bats. It’s worth noting as well that this group excludes our closest relative, the chimpanzee, who seem to enjoy anything but monogamy. In fact, it excludes the entirety of the ape family altogether, suggesting that monogamy might have been lost somewhere along the evolutionary line and popped back up in us humans.

As cute as it sounds, forming a life-long pair bond with a suitable partner does not necessarily mean that neither of the two will stray at some point. True sexual fidelity is quite hard to find in the animal kingdom. Not too long ago it was believed that almost all bird species mated exclusively with their partner, but recent research and observations suggest that although many of them do form life-long bonds, 90% will also mate outside of their partnership. The Seychelles Warbler is a prime example of a species that once appeared to be truly monogamous, until scientists observed several of the females sneaking into the bushes with their more attractive neighbours, leading them to discover that 70% of the eggs laid that season were fertilised by someone other than their partner.




So where does this leave us humans. Do we have it all wrong wanting to find someone special, fall in love and settle down?  Not necessarily. In fact, monogamy might be the reason that we’ve made it so far as a species. Through the examination of ancient human fossils, researchers at the University of Liverpool were able to determine that a change in sex hormones in early humans caused a shift from polygamy to monogamy 3.5 million years ago. As a result of this switch, parenting styles changed as fathers became more involved, providing their newborn babies with more food than they were receiving before. This supply of more nutrients and proteins is believed to be a monumental moment in human evolution, as it fueled the growth and development of the human brain, further separating us from our ape relatives and the rest of the animal kingdom.

Since then, monogamy has been firmly ingrained into many cultures. Not everyone may agree with it, but it has certainly helped us get to where we are today and continues to provide benefits to people. So maybe the desire that some people feel to cheat on their partners is a primal drive from our ancestors that has stuck around through millions of years of evolution?


Whatever the reason, it’s a firm reminder that we are in many ways still members of the animal kingdom.



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