Is there an evolutionary explanation as to why humans cry when they are upset?

Question

Evolution theory explains much of human behaviour, and I was wondering if anybody had one for the purpose of crying and tears and why it is triggered by being emotional or upset.

Answer 1

Yes ---

Crying is seen as an expression of emotion - we cry when we are sad and sometimes when we are happy as well, as in "weeping with laughter".

The tears we cry are produced by small glands above our eyes (called "tear glands") and then travel down tubes called "tear ducts" which open onto the eye under our upper eyelids. The tear ducts deliver tears near the outside of our eyes and the tears flow down and inwards towards our nose. Here there are small drainage tubes at the end of our lower eyelids and these take the tears down into the nose (this is why when we cry our noses run). This flow is used to wash away any unwanted particles that get onto the surface of your eye - usually when you have something in your eye, your eyes will water and the offending particle ends up nearer your nose.

Tears contain chemicals, most notably salt, which are used to clean the surface of the eye and kill any bacteria or other bugs that may be on the surface of the eye.

Thus, the biological response to anything unpleasant in or near the eye is to produce tears. The tears are produced by small muscles near the eye squeezing the tear glands and we can do this deliberately by screwing up our faces so that our eyes water. These same muscles are also linked to centres in the brain that control how we deal with unpleasant things and other stimuli that produce strong emotions - again crying through fear, pain etc is common and is designed to happen in case the eyes are also threatened.

Some people cry much more readily than others - it's not that they are somehow weaker or more emotional, just that their "crying reflex" is stronger.

There are conditions where your eyes will water continuously - most commonly if you have something irritating your eyeball or the inside of your eyelid, such as a foreign object stuck there or an infection or irritation such as hayfever. you may also suffer from the drainage ducts leading to your nose being blocked so your tears overflow from your eyes and run down your cheeks (this happens naturally if you cry more tears than the drainage ducts can cope with).

Answer 2

Good question, Tung.

I like what GLH said, and I also like what oldgruffgrump had to say. However, I am going to speculate a little and diverge from their opinions.

I think that crying is a social signal, just like the huffing sounds we emit when we laugh. Laughter is a signal indicating play, and it alerts our companions to the fact that we are not committing aggression, but rather playful acts.

Crying doesn't only happen in children, it happens to anyone who needs sympathy and help, including adults. I therefore postulate that
1) Crying mimics the pain suffered by someone who has been hurt physically,
2) Crying would stimulate a helping response from companions (that is, companions who share some genes, most likely being family) and
3) Encourage the companions to cease any aggressive actions.
4) This would work if the crying reaction, useful for removing foreign objects from the eye, was already an established physiological reaction, one which was understood by humans as a sign of injury requiring assistance.

Thus, I think that crying would be a useful tool to stop fights between people who share genes (or who share offspring), thus allowing some potentially fatal fights to terminate. The benefit of this, to the cryer, is that they live and pass on their genes. It thus is a beneficial adaptation, more likely to be passed on.

The fact that women cry more often than men suggests that this behavioral adaptation could help stop physical fights between men and their wives.

Answer 3

Great question! Have you read some of the writings of Richard Dawkins and Daniel Dennett? The probable explanation is that crying evolved as a useful behavior for young animals (including people) to get attention from their parents when they needed something (food, protection, whatever). It has less value for adults, but the behavior persists in adults because we are psychologically wired pretty much the same as children.

By the way, that might be the reason why televangelist Jan Crouch cries all the time on TV. She's scared that people will figure out that she's an idiot.

Answer 4

I recently read a suggested explanation for crying behaviour in humans; in short, it mimics the behaviour of a __very__ newborn baby, and thus elicits the care of adults nearby!

I forget where I read it (sorry!)

They pointed out that a newborn must attract the attention of adult humans, to get the care it needs, at birth. It has a wet face, is gasping for air (trying to breath for the first time, while the ductus arteriosus is still patent), it has a screwed up face, and seems helpless. So does a sobbing older human!

It was suggested that those older humans who just happened to react like that, when deeply distressed, received more care and attention and assistance, and were more likely to survive the emergency, and thus the trait was passed on.

Well, it COULD be true.

Answer 5

I happen to partially agree with all that has been said here. But I do have a question: if the above theories are true, than why people also cry when they are alone? Is there a theory to explain this? Is it because man is also a social actor for himself, not only for the others?

"How cheerfully on the false trail they cry!"
"Cry to be heard, as ’twere from heaven to earth"
Shakespeare--Hamlet

Answer 6

"no longer something evolves for the stable of the species...," is, in actuality, a pretend fact. you will see that maximum land animals do no longer consume their very own sort. it rather is, after all, a remember of what advances the genes, no longer the guy. Genes are shared in a collection, and valuable group behaviors strengthen the prospect of those genes propagating. The close by human tendency in the direction of compassion may be seen in this easy. Morality can come from that.

Answer 7

Here's an article dealing with 'searching for evolutionary purpose behind the tears' you'll want to read: http://www.signonsandiego.com/uniontrib/20050316/news_1c16crying.html

Hope that helps!

Answer 8

when visions are sad, tears are formed to wash them away

Answer 9

Maybe

Answer 10

may be but it is really a relief