Are Humans The Only Animal Species That Cries?

Why do we cry? Faced with overwhelming joy or grief, our eyes well up and tears stream down our cheeks. Crying is one of the most defining human experiences one can have. And yet, it's an evolutionary oddity. Plenty of animals produce tears to lubricate the eyes or flush out irritants. Human tears perform the same function, but the kinds of tears that are tied to feeling seem to be wholly unique to us. The general scientific consensus is that humans are the only species known to shed tears for emotional reasons, in which our feelings can quite literally leak out of us. It's a phenomenon that seems both universal and inexplicable, and one that has puzzled scientists for decades.

Scientists categorize human tears into three types: basal tears, which keep the eyes from drying out; reflex tears, which respond to irritants like dust or chopped onions; and emotional tears, which emerge in response to intense emotions. The first two occur across the animal kingdom. But humans are the only species we know of to tie tears to psychological states.

What makes this all the more mysterious is that no one knows exactly why we evolved to cry emotionally in the first place. There's no clear survival benefit to leaking saltwater when we're overwhelmed. Emotional crying uses energy, leaves us vulnerable, and doesn't help us escape danger or find food in any obvious way. And yet, it's such a deeply embedded part of the human experience that we often measure the depth of emotion by whether or not it moves us to tears. So, what exactly is going on here? Scientists have been wrong about human biology before (like that time we were off about human evolution by 40 million years). Could we be missing a key piece of the crying puzzle?

Despite decades of research, scientists still don't entirely understand why humans developed the capacity to cry emotionally (and no, it doesn't have anything to do with the pink part of your eye that's actually useless). One leading theory suggests that tears act as a social signal, a literal nonverbal cry for help that can prompt empathy and support from others. Tears visibly mark emotional vulnerability, which may have strengthened social bonds and increased the likelihood of cooperation and caregiving in early human communities. In that sense, crying may even be an example of group selection, in which evolutionary traits evolve at the level of the group rather than the individual.

Another hypothesis links crying to the regulation of emotion, pointing to the autonomic nervous system, the part of the body that mediates functions such as pupil dilation, heartbeat, and other involuntary actions. Jay Efran, emeritus professor at Temple University, argues that crying is like laughter — both arise when the body shifts between intense emotional states. In general, researchers agree that crying is our way of releasing built-up emotional burdens.

There's also the theory that crying gets rid of toxins and certain stress hormones in the body, an idea most strongly advocated by the biochemist William Frey. However, other researchers dispute this claim, arguing that the amount of toxins expelled through crying is too small to make any significant difference in our emotional state. So, the likeliest explanation for human crying is a mix of social signaling and emotional regulation. But what about other mammals? Certain animals are highly emotionally and socially intuitive. For example, dogs may be able to tell if someone dislikes their owner. Is it beyond the realm of possibility that other animals may cry emotional tears like us?

Many animals vocalize when distressed, show grief, and display physical signs of sadness. As far as scientists can tell, however, humans are still unique in our shedding emotional tears. But what about the case of Raju, an elephant that was rescued from 50 years of abusive captivity in Uttar Pradesh, India, in 2014? As rescuers removed Raju's spiked shackles, they reported seeing tears pouring from his eyes. Elephants are known to mourn their dead, and there is evidence that they bury their young. Some scientists, such as Marc Bekoff, emeritus professor of ecology and evolutionary biology at the University of Colorado, argue that elephants do cry like humans, and that researchers should be more open to that possibility.

Dogs are another fascinating case. In 2022, researchers at Azabu University in Japan published a study showing that dogs produce more tears when reunited with their owners after long absences, likely due to a rush of the hormone oxytocin. Still, the study only links emotional arousal and increased tear volume in one species, and doesn't confirm emotional crying as humans experience it. 

The problem lies in our inability to scientifically confirm or deny the quality of an experience that another animal is having. We can't inhabit their minds, and debates about animal consciousness aside, this makes emotional states difficult to verify. There's also the risk of anthropomorphizing animals — assigning human qualities and experiences to them that they might not have due to the bias of our own experiential lens. However, the opposite risk also exists: assuming that animals don't experience the world in similar ways to ourselves simply because they are not human. For now, emotional crying remains a distinctly human mystery, but the capacity for deep feeling clearly isn't ours to lay sole claim to.