Is there a purpose?
In: Biology
Tears contain tiny amounts of a very powerful pain-killing compound. It’s literally an act of self-soothing. Very useful for an organism with emotions that can go haywire.
Aside from the answer given the other “biological” (I deem this as why evolution made it that way) is because it expresses sadness without any form of language. Like all of our muscles that allow us to make facial expressions tears help convey emtoions, which is incredibly useful for our species which has evolved with social ability in mind.
Someone has already mentioned the small dose palliatives in tears, but that’s only part of the answer. Crying comes before language, and is a way for infants to communicate that they need something.
You will usually find after a good cry, you tend to feel better. That’s because it’s a reflex of self-soothing that releases endorphins that chemically makes your brain calmer, lessens pain and makes you feel better overall.
The biological purpose has nothing to do with sadness, it’s to help get stuff out of your eye that doesn’t belong to, and it’s triggered by pain. As far as I know and from personal experience with pain medication, physical and psychological pain are very similar. Maybe there is a connection
Tears provide a visible signal that you are in pain, that can be silent.
EG, you’re hunting a sabretooth tiger with your caveman buddies, and you hurt yourself. The other cavemen see your tears and know you’re hurt, you didn’t have to make a sound which could be heard by the sabretooth tiger.
The stuff that deals with pain don’t really distinguish between physical pain and emotional pain.
So that’s why your body goes through a bunch of physical responses to emotional pain when you are sad, including crying.
What about when crying with laughter!?
When you become aroused, emotionally or physically, your sympathetic nervous system increases its activity. Your sympathetic nervous system is identical to many other animal’s in that it increases in activation when you need to fight, run away, or freeze up until the danger passes. Your heart rate goes up, you breathe harder, and blood rushes from your guts to your extremities so that you are prepared to survive whatever life is throwing your way at the moment.
Crying is a by-product of the activation of the parasympathetic nervous system. The parasympathetic nervous system ramps up activity when your sympathetic nervous system is ramped up (usually when you’re very happy, very sad, very angry, or very nervous). As activity increases in the parasympathetic system, it decreases activity of the sympathetic nervous system, so that you won’t die from your heart and respiration rate going up beyond the danger zone for an extended period of time.
In sum, crying is regulatory: you cry to lower your heart and respiration rate, and it also allows for the re-activation of the parts of your brain that were shut off (most importantly, the logical problem-solving part of your brain) due to extreme activation of your flight/fight/freeze response to something that stressed you out.
I’m guessing, more of a function for small babies and infants.
Crying alerts parental figures that you need attention. You’re either in pain, need food, or have a poopy butt.
Good article [here](https://aeon.co/essays/the-original-meaning-of-laughter-smiles-and-tears) that goes through a theory from a social standpoint, possibly linked to the biological question from OP
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