If you've ever cried when you really, really didn't want to (and who hasn't) you may have wondered what crying does for humans, aside from let us publicly display our snottiness on public transport and get sympathy from old women. We've been wondering about the functions of crying for years; Charles Darwin, frustrated by their apparent uselessness, declared crying purposeless, and it's only recently that we've begun to prove him wrong. Crying, it seems, serves a variety of purposes, though some of the old wives' tales about how it works may actually not be viable when scrutinized using science.
Research in 2010 found that laughter and weeping are quite universal human emotions, though the social conditions in which they occur can be very different (taboos on masculine crying, for instance). Why did it evolve? What on earth prompts us to push the ordinary lubrication of our eyes, necessary for its proper moisturizing and health, out in big dollops at particular intervals in our lives? It's a bit weird, if you stop to think about it.
The good news is that science is up for explaining it. If you got an attack of the raining-on-my-face when watching Vice President Joe Biden get the Presidential Medal Of Freedom, for instance, there's solid science to explain what was happening to you, aside from being a big old softie.
It Enhances Relationships
One of the functions of crying, it seems, is a social signifier of vulnerability: tears signal something to other people, even if we try to hide them. Research from Tel Aviv in 2009 found that they can help us out in social situations. If somebody is antagonizing us, they're meant to inspire sympathy; people are more likely to empathize and offer help if they see tears; and if you cry in a group at a funeral, the act can be a "validation of emotion," bringing you closer together.
As much as we might conceive of crying as a solitary act alone in our rooms, it also functions very socially. Cultural contexts matter to this, too; 2007 research found that, since September 11 in particular, American culture had become more accepting of adult demonstrations of emotion via crying, and male ones in particular. But cultural ideas about masculine crying still matter. People exposed to a range of images of people crying felt most strongly about men with a gentle moistness in their eyes, rather than full-on bawling. It's not "supposed" to be how men communicate. (Just one more way gender norms screw us — and President Obama has helped combat them, by crying publicly.)
Crying Evolved To Help Us Bond & Attract Attention
So did crying evolve to help us with social situations? There are a few different theories flying around. One is that crying from empathy with others' suffering is part of our success as a species because it's a result of empathy, our ability to feel for and therefore be moved to help others, even if we don't know them personally. That kind of altruism likely helped us survive as a species. Another is that tears were a valuable form of social communication of emotion before the development of language, helping us cement our relationships, identify with others, and show grief and happiness in elaborate ways. Given that early humans subsisted in groups that were heavily reliant on each other, tears may have formed early relationships long before anybody knew how to say "I'm so sad."
The most evolutionarily necessary crying, according to scientists, is likely the crying of tiny babies, who don't have any other way to communicate. According to psychology professor Debra Zeifman, it's been a good strategy, in that it gets peoples' attention, might scare off curious enemies, and communicates needs — though it's not entirely unproblematic. "On the negative end," she notes, "crying is metabolically costly and may attract predators and annoy caregivers." Crying, in other words, hasn't necessarily been without costs in the evolution of humanity, but we haven't come up with anything better.
It May Chemically Signal Our Need For Comfort (And That It Isn't Sexy Time)
There are a few interesting theories about the chemical composition of tears and what it does for us and other people. One experiment, in 2011, had men who sniff the tears of crying women and then rate female faces for attractiveness. Researchers found that the men found the faces less attractive after a tear-sniff, even though they didn't know what the substance was. The reason, the scientists think, is that when we're around a partner who cries, our bodies respond not with arousal but with the recognition that they need comfort.
What's in tears that might cause this response? Emotional tears, scientists have discovered, have a faintly different chemical composition to reflexive ones or normal eye lubrication. Looking at dried tears under the microscope reveals profound structural differences. While the idea that the chemicals exuded in tears might do anything to the mood of the person crying is still debated by scientists, it seems that people around the crying subject might pick up on something interesting.
No, It Doesn't Always Make Us Feel Better
It seems that the way in which we believe tears function emotionally has a lot to do with our beliefs about crying in general. In 2015, people were asked to self-report on their emotions after watching a sad film, and those who had cried said they experienced better emotions following the crying episode. But, as other research has shown, this is likely because of the circumstances surrounding crying and beliefs in its cathartic nature.
In 2008, a vast survey of over 3,000 recent crying experiences by scientists revealed that there are a lot of variables that determine how we feel after crying. They identified some big ones: the social situation in which crying occurs, the personality of the crying person, and what they felt their emotions to be at the time. It seemed that the physiological effects of crying can be both positive (a slower breathing rate) and negative (increased stress on the body), and that how those symptoms manifest, and how we react to them, depends a lot on where we are at the time. Surrounded by friends rubbing our back and telling us we'll be fine? Probably cool. Alone, or being yelled at, or in a context where you're deeply uncomfortable weeping? Not going to feel so great after.