I’m so surprised that so many people are convinced that monogamy—heterosexual, human monogamy, in particular—is some type of biological default.
Over the past few weeks, I’ve been hearing quite a bit about monogamy—especially within the context of human marriage and what is supposedly “natural.” I use the quotes intentionally. Mostly because I’m so surprised that so many people are convinced that monogamy—heterosexual, human monogamy, in particular—is some type of biological default.
Science doesn’t quite back up that notion. (Though, admittedly, it has not been studied as in-depth as many would have you believe).
Let me explain. Only about 3% of mammalian species demonstrate monogamous behavior. 3%. That’s a pretty paltry number. And those few animals that do exhibit monogamous behaviors only demonstrate what scientists call socially monogamous behavior. The modifier is important, and I’ll get to that in a moment.
Prairie voles (Microtus ochrogaster) might well be the monogamy poster children. These small, furry rodents not only happily burrow underneath meadows in the American Midwest. Male and female prairie voles mate for life, working together to take care of pups. These animals are the model of choice for studying monogamy and pair-bonding behaviors—and when you see headlines touting the latest neurobiological research on monogamy, chances are there were a few prairie vole brains sacrificed to get those findings.
Neurochemicals like vasopressin, oxytocin and dopamine have been linked to forming strong monogamous bonds. And some have suggested that perhaps we can even create a love drug (or vaccine, depending on your particular frame of reference) using those chemicals to strengthen our relationships. Such pharmaceuticals could ensure that everyone is living within that expected monogamous default.
There’s only one problem. Our monogamy poster children, those lovely and talented prairie voles, are not sexually monogamous. Remember my use of socially above? While they do mate for life, and take quite good care of one another, they aren’t above occasionally getting some side action. Yes, prairie voles cheat.
When Alexander Ophir, a researcher at Oklahoma State University, looked at the genetic links between prairie vole pups and the Mom/Dad pair that was raising them, he found something interesting. Approximately 20% of those pups were not related to Mom’s pair-bonded partner. Think of Ophir's study as the prairie vole equivalent of “You are not the father!” from the Maury Povich show. Out in the wild, outside controlled laboratory conditions, prairie voles, while devoted to their pair-bonded partners, are not sexually monogamous.
It may be time, especially given the way American has politicized the concept of marriage, to rethink monogamy. Because just as prairie voles aren’t as pure as the driven snow, there is also no biological evidence to suggest that human beings are naturally monogamous. We may be culturally and socially encouraged to be faithful but it is unclear how much that sway really has over our biology.