Saturday, May 19, 2012

Why did we evolve to cry tears?

We all cry some time or other. Sometimes when we are hurt physically, and sometimes when we are hurt emotionally. As young children we make crying noises along with tears. As we grow up, we learn to weep silently. And sometimes our eyes get tears without us making any noises.

If you believe in the theory of evolution, everything we are today must have a reason, right? Unless there was some evolutionary advantage in shedding tears, we wouldn't have evolved to cry. So what is it?

Let's trace a possible evolutionary path we might have taken.

Let's think of a newborn baby. A human baby needs to be tended to by its parents, but the baby must be able to communicate a few simple messages to help them. To start with, it needs to indicate when it is uncomfortable (for any reason like hunger, cold, hot, pain) and when it is content. It will take the baby quite some time to learn to speak, but what the hell, it can yell out in the meantime! So that's what babies do, squint their faces and let air out from their lungs to make the crying sound. The louder they cry the harder they squint.

A hard squint squeezes the tear gland and releases tear drops into the eye. So while just a crying sound indicated some discomfort, tears definitely indicated great discomfort. A baby who cried tears got more attention than a baby who just made noises. So they got fed more, got stronger and had more children than others who did not shed tears. Slowly, the brain evolved to link the emotion of discomfort to the tear gland. Such a linkage allowed the brain to 'cheat' and shed tears more easily.

Once emotion got linked to it, it became sort of involuntary for us. It was partly under the brain's control. Like the wag of a dog's tail.

A grown up child who can speak doesn't need to cry to indicate discomfort. It can do much better by telling what exactly is bothering him/her. So grown up children do not cry if they can communicate their discomfort. It is easier and faster to fix the problem that way.

But sometimes it is not possible or difficult to communicate. Either because the other party is refusing to understand, or it is something that is difficult for the child to explain effectively. That is when the brain brings out those tears, sometimes also accompanied by cries. They are intended for the people watching him/her, they would then know that the pain that the child is experiencing is more that what their physical actions show. In the history of evolution, children who could do this definitely got a better deal that others who could not. So we evolved to retain our crying till young adulthood.

When the child grows up even more to become an adult, it becomes emotionally more complex. Emotional hurt sometimes gives him/her as much or more pain than any physical hurt. Sometimes he/she may get emotionally overwhelmed by just thinking of something. Then, involuntarily, the brain kicks in the tears to display the emotions. If there was someone watching, they would sympathise with the person and do something to calm them or resolve the problem. Such people who could cry even as adults would get better emotional help from others than people who did not cry. They would be emotionally better off, and hence we evolved to retain our crying habits till adulthood.

Slowly it became such an important part of our complex emotional framework that sometimes just crying out without anyone seeing us also calmed us down. It served as an emotional vent to let off some grief.

And of course, being humans with high IQ, we quickly learn to cheat, even ourselves. Sometimes with a bit of effort, some of us can bring out false tears. That is like lying to get certain advantages, but we have learnt to do it as well.

And by the way, if after reading this you are thinking that people who cry easily get everything easy, you are wrong. Unnecessary and frequent crying puts off people around and can have negative results!

Wow! Such uses of some silly small drops of salt water!

Some things to ponder on:
- why do we laugh?
- why do tears come out when we are too happy?
- do animals shed tears?