The people redefining faithfulness

We often see a relationship as an exclusive understanding between two people. But this norm is increasingly coming under scrutiny as people find other ways to redefine romantic love.

To put that in perspective, 21% is slightly less than the number of US households who speak a language other than English at home (21.9%). “I wouldn't be surprised if it was more common,” says Amy Moors, assistant professor of psychology at Chapman University, California. “Something called social desirability explains why people give slightly conservative answers to questions. It might be why someone overestimates how often they eat five fruits or vegetables a day, or underestimates how much they drink.”

For that sizeable minority, the opportunities to meet with partners outside their household may be few right now, as measures to prevent social interactions step up in countries affected by the Covid-19 outbreak. People in CNM relationships might find themselves spending a greater amount of time with their live-in partners while having to get used to seeing their other partners a lot less. How this will affect their wellbeing is unclear, although well-established research on long-distance relationships suggests that long-distance relationships can be perfectly fulfilling. And, as social psychology tells us, in more ordinary times there are reasons to believe that people in CNM relationships may experience advantages their monogamous peers do not.

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At what point monogamy began to occur in humans is up for debate. Some anthropologists cite the fact that ancient human ancestors were strongly sexually dimorphic – that males and females were different sizes and shapes – as evidence of non-monogamy. A high degree of sexual dimorphism suggests that there are strong sexually selective pressures on one (or both) genders. In some species, like gorillas, larger males are more likely to be sexually successful by using their greater size to fight off competition from other males. A dominant male mountain gorilla will monopolise 70% of all copulations, for example, creating a polygynous society (one where many females mate with one male).

Sexual dimorphism does not always work this way. Species that use ostentatious displays of fitness, like birds with beautiful plumes and brightly coloured fish, compete for the attention of mates, rather than physically fighting off competition. The difference here is that often these are not social species, unlike humans, so one male or female would not necessarily be able to control all of their potential mates in one area.

The ancient human fossil record is patchy, though. Similar logic is also used to argue the exact opposite – that our ancient relatives had a similar level of dimorphism to us. This can be justified by looking at  different fossils. Therefore monogamy might have first occurred much earlier.

The diversity, or lack-thereof, of the human Y-chromosome has also been used to suggest that humans were polygynous until relatively recently. Again, anthropologists contest the evidence, but some have suggested that the relative similarity in male genetic data suggests that only a few males were mating in our evolutionary past. More recently, this diversity has increased, which suggests that more males have been able to mate because of monogamy.