Did John's genes make him cheat on Elizabeth?
Photo by Mike MurphyI've brought up before how genes can affect our behavior. They don't necessarily determine what we do but they can make doing the "right" thing easier or harder. A new study suggests that having a certain version of a certain vasopressin receptor gene makes a man less likely to cheat on his partner.

The gene commonly comes in three different versions — RS1, RS3, and GT25. Men with GT25 and RS1 reported more infidelity and had unhappier marriages on average than men with RS3. Which version a woman had didn't seem to matter.

Scientists don't know why men with the RS3 version are more faithful but it makes sense that this gene would be involved. It has been implicated in pair bonding in other animals with the best and most comprehensive work having been done on little rodents called voles.

There are many different kinds of voles but we’ll focus on prairie and meadow voles. Prairie voles stick with one female. Meadow voles are a bit more like men in country music songs — they tend to love them and leave them.

A bunch of wonderful experiments showed that the voles' different behaviors were because they had different versions of a certain vasopressin receptor gene. People don’t have the exact genetic difference that meadow and prairie voles have. But the exact same gene is involved in this new study.

The vole experiments showed that if the vasopressin receptor works less well in prairie voles, the boy voles develop a wandering eye. And male meadow voles with extra potent vasopressin receptors settle down.

So at least in voles this vasopressin receptor gene is important for pair bonding. We'll need more studies in humans to nail down whether it plays as big a role in human male monogamy. But this study does bring up some interesting ideas.

First off, we aren't voles so having this gene is no excuse for cheating on a partner. It just means that it is harder for these men to remain faithful. Sorry John but even if you have this gene version it doesn’t let you off the hook for cheating on Elizabeth.

Second, if the study proves to be correct, then it suggests that there may be a pharmaceutical way to modify men's behavior. A pharmaceutical company would need to come up with a drug that targets this receptor. Now men who take this drug would be more likely to be faithful. I don’t know about you, but this form of pharmaceutical behavioral modification seems a little scary to me.

It's tricky to talk about pharmaceuticals in the drinking water without risking two really unfortunate side effects: 1) Make people panic that their tap water is unsafe. 2) Send listeners running to Costco to buy pallet-loads of overpriced, highly packaged, and often dubiously-sourced bottled water.

You can never really say enough about everything that's wrong with bottled water (which, by the way, adheres to lower safety standards than what comes out of your tap-– sorry, couldn’t resist!). But when it comes to drugs in the water, what strikes me as most interesting is what we know the least about: What do these tiny, tiny amounts of drugs mean to us humans?

"The dose makes the poison" is a mantra I hear constantly from public health experts (as well as my editors)– and it's worth considering. In other words: just because something exists does not mean it's affecting you. It's likely we're exposed to far more toxins in the act of, say, applying nail polish, or pumping a tank of gas, than we'll imbibe over a lifetime of drinking tap water. But it'll be interesting to watch this play out over the next decade or so, as scientists on all sides of the debate try and figure out what exactly effect our environment-– pharmaceuticals, nail polish, plastics, and countless other everyday substances– is having on us.

Listen to the Drugs In Our Drinking Water Radio report online.