Anthropologist explains why we cheat on people we love

There's the sex drive, which is like an "intolerable neural itch," to get us out searching for a range of partners to help pass on our genes. There's romantic love, which helps us focus our mating energy on one person. And then there's attachment, the calm and security we feel with a long-term partner so we can raise children with them as a team.

However, those three brain systems, sex drive, romantic love, and attachment, aren't always connected to each other.

So it's possible to feel deep attachment to a long-term partner at the same time you feel intense romantic love toward someone else and even also feel sexual attraction toward another person, Fisher said.

"In short, we're capable of loving more than one person at a time," Fisher said.

And that's why, Fisher says, some people may cheat on their partner.

It's why someone can lay in bed at night thinking about deep feelings of attachment to one person and swing to thoughts of romantic love for another person.

"It's as if there's a committee meeting going on inside your head as you try to decide what to do," Fisher said. "I don't think honestly that we're an animal that was built to be happy — we're an animal that was built to reproduce. I think the happiness we find, we make."

This all sounds like a cynical take on love, but Fisher says that, despite all these straightforward and unavoidable biological processes, there's still mystery and "magic to it."


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