It’s pretty obvious when a dog is sad. It might whine or whimper, knit its brow, or turn its big, imploring eyes upward at you. But it would be another thing entirely to see a big tear rolling down your canine companion’s face.
Animals simply don’t cry. Or at least, they don’t shed emotional tears. The only creatures who have evolved to do so, it turns out, are humans. We snivel at sad movies, well up at weddings and blink away hot tears of frustration during arguments. “We appear to be the only animal that sheds tears for emotional reasons,” says Randolph Cornelius, a professor of psychological science at Vassar College in New York and an expert on human emotion.
There are many theories on the evolution and purpose of emotional tears. Experts even have a few ideas why animals — who do experience emotions — don’t weep like we do. But why we evolved to eject liquid out of our eyes as a signal of distress, rather than some other reaction, is still far from settled.
