From Friday’s BBC Science in Action podcast is more on the biology of love. According to research presented by Lucy Vincent (neurobiologist at the French Scientific Research Center) and Dave Perrett (Professor of Psychology at the University of St. Andrews), one of the many factors that stimulate attraction and feelings of deep affection is the hormone oxytocin, more specifically the density and activity of oxytocin receptors. Okay, so that much has been known for years. However, Dr. Vincent goes on to say that these oxytocin receptors are very prevalent only for about three years in humans. Not only that, but as the oxytocin receptors become less dense and/or functional, receptors for vasopressin seem to take over, producing more of an “enemy” response rather than affection (though she admits the “enemy” thing is a substantial extrapolation).

According to the good doctors, this seems to fit with evolutionary pressure derived from the extreme vulnerability of human infants, which require(d) two parents to take care of and protect them full-time. However, after 12-18 months the infant becomes significantly less vulnerable (able to stand and perhaps throw off a bird or small animal attacking it), at which point only one parent would be necessary. And at that point, the oxytocin effect more or less ceases, yielding to increased vasopressin receptor activity- essentially a biochemical foundation for why people tend to “fall out of love” after a few years. Pretty heavy.

Professor Perrett adds that strong parent-child bonds tend to be transgenerational, and that many girls from families without strong bonds not only reach puberty earlier, have less stable relationships, and marry and bear children earlier, but also tend to have less dense oxytocin receptors.

Both researchers agreed that, while potentially a big downer, it’s certainly better to know what’s going on up there. Or at least, to know there’s a biochemical basis for why love wanes and it’s not all like “Oh crap, i’ve made a huge mistake.”

I wasn’t able to find any actual articles on this, just the BBC podcast so if any of y’all stumble across one, send it my way.

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