Why Do Humans Fall In Love? An Evolutionary Biologist Explains

InnovationScienceWhy Do Humans Fall In Love? An Evolutionary Biologist ExplainsByScott Travers,Contributor.Forbes contributors publish independent expert analyses and insights. I write about biodiversity and the hidden quirks of the natural world.Follow AuthorJun 05, 2026, 08:30am EDTThe science behind love, one of our most disorienting and euphoric experiences, is stranger and more ancient than you might expect.gettyIn a 1992 study, a team of neuroscientists made a discovery that, technically, had nothing to do with humans. They were studying prairie voles (Microtus ochrogaster), small, unremarkable rodents common to the American Midwest. They found something genuinely strange: when researchers blocked the action of a hormone called oxytocin (known colloquially as the “love hormone”) in female prairie voles, the animals failed to form pair bonds with their mates. Interestingly, when they manipulated the related hormone vasopressin in males, they could accelerate bonding or, just as easily, prevent it altogether.What made this odd weren’t the prairie voles themselves, but how they compared to others. The meadow vole (Microtus pennsylvanicus), a nearly identical species, is promiscuous; it doesn’t pair bond at all. The difference between a monogamous rodent and a promiscuous one came down not to some grand moral distinction, but to the density of hormone receptors in specific regions of the brain’s reward circuitry. Ultimately, the distribution of vasopressin receptors in the nucleus accumbens, a hub of the brain’s reward system, was the key variable. Move those receptors, and you could effectively move the animal’s entire social life. So, why should you care about these prairie voles? Because this tiny study opened a window into a much larger, older question: Why do we fall in love at all? To answer that, we need to go considerably further back.Love As A Survival Strategy It’s tempting, and perhaps a little deflating, to learn that romantic love, that most intensely...