Read the full article at The Washington Post.

The pain started on the way down the mountain, a dull ache in my chest that became more acute as the miles accumulated. The morning had been a blur of hungover goodbyes as a three-day camping wedding of close friends came to an end in Northern California. It wasn’t until I was in the quiet safety of a friend’s car that I allowed myself to feel the effects of my conversation with my date the night before.

He had told me he wasn’t interested in trying a relationship. Remembering it made the pain intensify. By the time we reached the interstate, I was in tears.

We tend to think of heartbreak as purely emotional pain but forget that we give it a physical dimension with our term for it. Some feel it in their chest, as I did; others feel it as a stomachache or a more diffuse pain all over the body. Humans seem to have been feeling it since at least the 1300s, when the word “heartbreak” first made an appearance, according to the Oxford English Dictionary. Several languages have a similar word translating to something like “heart pain.”

Social scientists believe that the phenomenon has been around for much longer, possibly millennia. Like grief, our physiological response to rejection is triggered by some of our deepest survival instincts. Humans are herd animals who depend on one another to survive. To keep us from drifting away from the fire every time we had a disagreement, our brains developed a physical alarm system that warned us when we got too far from the people who helped keep us alive in the wilderness.

“A social rejection hijacks the part of our brain that signals pain to say, ‘Hey, this is a really serious situation,’ because just like physical pain, the consequences could be there,” says Ethan Kross of the University of Michigan’s Emotion & Self Control Lab. In 2011, his lab conducted a study in which researchers showed participants pictures of an ex-partner who had broken up with them. Seeing the photo activated the same brain regions previously thought to be specific to the experience of physical pain. Other emotions, such as anger, don’t do that.

But that doesn’t mean emotional and physical pain are the same thing, Kross cautions. Even though physical pain and rejection activate the same parts of the brain, they have different neural signatures, which is why humans can tell the difference between the agony of a broken leg and the sting of a social slight.