The Evolution of Tears

NLN · Mar 14, 2007

Darwin struggled with the evolution of tears: what evolutionary advantage could come of secreting water from the eyes? I thought about this, and suggest the following answer.

Tears are both an expression of sorrow/grief—and also a grand visual display of grief—meant to be viewed by others. Think about what happens when you see someone crying: there is an immediate response from the gut; we feel great sympathy, and if we were angry before, our anger dissipates.

I think this explains why the display of tears evolved: to show resignation and submission to an opponent; to relieve tension between warring individuals—and therefore enhance the weaker one's chance of survival.

What do you think?

elvenwanderer111 · Mar 19, 2007

Hmm... Why do we tear up when we laugh? I am usually not sad when I am laughing

NLN · Mar 19, 2007

Good point. Tears in laughter too have something to do with a display to others—as both tears in sorrow and tears in laughter bring immediate responses from viewers. Perhaps tears help visually reinforce each of these strong emotions.

Mallon · Mar 19, 2007

I doubt very much if 'tears of laughter' have much adaptive significance at all. Read the 'spandrels' work of Gould and Lewontin with regards to the atomization of the body and the adaptationist programme.

elvenwanderer111 · Mar 19, 2007

I def need to read up on this evolution of tears, i see no way in how this proves evolution, or even that tears are evolved

NLN · Mar 19, 2007

Thanks for the book recommendation. I'll look into it.

vernee · Jul 13, 2007

I don't always feel sympathy when I see others cry. Sometimes I think its pathetic what they cry about. I might even laugh in their face if I do think its pathetic. So I don't think this applies to everybody. Why did we start crying because we're hurt but the tears come after the cause leaves?

pgp_protector · Jul 13, 2007

I thought the primary reason for tears was in keeping the eye clean & removing debre from the eyes.

NailsII · Aug 12, 2007

Tears are used to cleanse the eye, containing Lysozyme they are effective at killing a large portion of bacteria. However, most pathogenic bacteria have evolved resistance to lysozyme, which is why Florey's work on penicillin bacame such big news in the 1940's.
My idea with regards to tears is quite simple, and is infant-driven but requires tear formation to have already evolved - note I am not discussing how an organism developed the tear secretion system, that is for another thread I thnk.
A young child cries and sheds tears, the mother really needs to comfort the child to reduce the risk of predation. A sequencial driving force ensues, the elders need to reduce a child's cries quickly and reduce the chances of attracting predators.
In short, any population that can quickly recognise a crying child as needing comfort is bestowed an instant (but small) evolutionary advantage.

NLN · Aug 12, 2007

That is a very interesting theory, NailsII, and one I haven't heard of before. Quite possible.

NailsII · Aug 30, 2007

NLN said:
That is a very interesting theory, NailsII, and one I haven't heard of before. Quite possible.

I suppose it is an extension of many other theories of this kind, most noatable of bird cries in the nest.
The mother bird will od anything to keep them quiet to the extent that whoever cries loudest gets fed the most....
In general!!

Radiata · Aug 30, 2007

Tears are just a strong display of emotion. That's all. They can be used in anything.

NailsII · Sep 16, 2007

Radiata said:
Tears are just a strong display of emotion. That's all. They can be used in anything.

....Which means that you basically don't believe that they evolved?

Radiata · Sep 16, 2007

NailsII said:
....Which means that you basically don't believe that they evolved?

No.

Inan3 · Sep 16, 2007

NLN said:
Darwin struggled with the evolution of tears: what evolutionary advantage could come of secreting water from the eyes? I thought about this, and suggest the following answer.

Tears are both an expression of sorrow/griefand also a grand visual display of griefmeant to be viewed by others. Think about what happens when you see someone crying: there is an immediate response from the gut; we feel great sympathy, and if we were angry before, our anger dissipates.

I think this explains why the display of tears evolved: to show resignation and submission to an opponent; to relieve tension between warring individualsand therefore enhance the weaker one's chance of survival.

What do you think?

What about tears of joy? What about tears of pain? What about tears of appreciation? What about tears of anger? etc.

Tears are linked to our emotions. They are in place to vent and release. I think they were placed there by God.

Inan3 · Sep 16, 2007

NailsII said:
Tears are used to cleanse the eye, containing Lysozyme they are effective at killing a large portion of bacteria. However, most pathogenic bacteria have evolved resistance to lysozyme, which is why Florey's work on penicillin bacame such big news in the 1940's.
My idea with regards to tears is quite simple, and is infant-driven but requires tear formation to have already evolved - note I am not discussing how an organism developed the tear secretion system, that is for another thread I thnk.
A young child cries and sheds tears, the mother really needs to comfort the child to reduce the risk of predation. A sequencial driving force ensues, the elders need to reduce a child's cries quickly and reduce the chances of attracting predators.
In short, any population that can quickly recognise a crying child as needing comfort is bestowed an instant (but small) evolutionary advantage.

What a sad life that one could not cry for joy, or love, or to release anger, and pain. If science keeps one so wrapped up as to not understand how to feel or why we feel or what happens when we feel, then they need to step back and look at what life if really all about.

NailsII · Sep 17, 2007

Inan3 said:
What a sad life that one could not cry for joy, or love, or to release anger, and pain. If science keeps one so wrapped up as to not understand how to feel or why we feel or what happens when we feel, then they need to step back and look at what life if really all about.

I merely expressed an opinion on one side of the discussion, I did not intend to answer every possible consequence and occurance. It is too time consuming and my leisure time is rather limited unfortunatley.
However, seing as you force my hand....
Tears are obviously a signal of communication from one human to another.
The origin of their development is quite obviousl pre-human, and serves the incredibly useful (neccessary, in fact) function of cleaning the exterior of the eyeball.
This is obvious by the chemical composition of tears; consisting of oils, water and mucus as well as lysozyme - an antibacterial agent.
Basal tears, those that are normally secreted automatically to lubricate the eye, and reflex tears, those used to flush the eye of irritants are obvious in origin - I need not to cover these.
You are specifically refereing to crying or weeping in responce to joy or sadness - I hae already discussed my ideas with regards to the later.
Tears of joy are often accompanied by a flush red face or laughter - increasing pressure around the lacrimal gland. This in turn leads to the secretion of a watery substance over the eyes.
Simple really, it doesn't even need an explanation as it could just be a by-product of other forms of behaviour.
I'm suprised you felt the need to even ask.

Inan3 · Sep 17, 2007

NailsII said:
I merely expressed an opinion on one side of the discussion, I did not intend to answer every possible consequence and occurance. It is too time consuming and my leisure time is rather limited unfortunatley.
However, seing as you force my hand....
Tears are obviously a signal of communication from one human to another..[/quote

Firstly, what about people who cry ALL by themselves? No one there to communicate with. And what about people who don't cry at all?

NailsII said:

The origin of their development is quite obviousl pre-human, and serves the incredibly useful (neccessary, in fact) function of cleaning the exterior of the eyeball.
This is obvious by the chemical composition of tears; consisting of oils, water and mucus as well as lysozyme - an antibacterial agent.

Basal tears, those that are normally secreted automatically to lubricate the eye, and reflex tears, those used to flush the eye of irritants are obvious in origin - I need not to cover these.

Click to expand...

Secondly, I agree with the part about tears cleansing the eyes.

NailsII said:

You are specifically refereing to crying or weeping in responce to joy or sadness - I hae already discussed my ideas with regards to the later.
Tears of joy are often accompanied by a flush red face or laughter - increasing pressure around the lacrimal gland. This in turn leads to the secretion of a watery substance over the eyes.
Simple really, it doesn't even need an explanation as it could just be a by-product of other forms of behaviour..

Click to expand...

What the flip? What is this Tears 101? Did you actually think I wanted an explanation of tears? I know about tears. I think anyone who is just beyond infancy knows about tears.

I'm suprised you felt the need to even ask.

I didn't! I was being slightly sardonic! I thought the content of your second quote above was more in line with what should have been the answer to "why tears" BUT seeing the OP suggested emotions of sorrow/grief and then the ridiculous notion of "Think about what happens when you see someone crying: there is an immediate response from the gut; we feel great sympathy, and if we were angry before, our anger dissipates. to show resignation and submission to an opponent; to relieve tension between warring individualsand therefore enhance the weaker one's chance of survival.", and then asked, "what do you think?", I thought, I would give my two cents, but I wasn't asking. I definitely was not asking.

I mean, WHAT world do they live in?

Imagine this....Warriors going to battle, full of anger and hatred, ready to kill, destroy and conqueor and THEN...the opposing side breaks down and cries , so the other side stops...drops their weapons and gives them a great big hug! NOT!!!!!!!

Do you suppose that anyone cried during the holicaust? But they were still massacred! Do you think POW's may have cried? or children or women being abused and killed? Need I say more?

As to the primitives it was survival of the fittest not the weakest. Unfortunately it still is.

NailsII · Sep 18, 2007

quote=Inan3;38902816]Firstly, what about people who cry ALL by themselves? No one there to communicate with. And what about people who don't cry at all?[/quote]
Children alone will cry so they are not all by themselves.
Adults doing it are probably following a learned pattern, it worked as a child so it could work as an adult.
Tears are known to produce hormone changes and relieve stress, so crying alone is not pointless.

Inan3 said:
What the flip? What is this Tears 101? Did you actually think I wanted an explanation of tears? I know about tears. I think anyone who is just beyond infancy knows about tears.

I'm sorry if it was too basic for you, given your previous posts about biology I assumed you don't have this basic knowledge.

Inan3 said:
I didn't! I was being slightly sardonic!

Derived from the Greek Sardonios which means bitter or scornful laughter: the primary reference is to the effects of eating a Sardinian plant which was said to produce facial convulsions resembling horrible laughter, usually followed by death.
www.mountainvalleygrowers.com/definitions.htm

Inan3 said:
I thought the content of your second quote above was more in line with what should have been the answer to "why tears" BUT seeing the OP suggested emotions of sorrow/grief and then the ridiculous notion of "Think about what happens when you see someone crying: there is an immediate response from the gut; we feel great sympathy, and if we were angry before, our anger dissipates. to show resignation and submission to an opponent; to relieve tension between warring individuals—and therefore enhance the weaker one's chance of survival.", and then asked, "what do you think?", I thought, I would give my two cents, but I wasn't asking. I definitely was not asking.
I mean, WHAT world do they live in?

You obviously don't have children or younger siblings then, or if you do then perhaps you are not very close to them. I wonder what Sigmund Freud would say about this.....
Tears is a prmary tool for youngsters to gain affection even when they have done wrong.
It is unfortunate that you have not experienced this.
And by posting you are effectively asking someone to read your words and answer them - it is in effect, the same as asking.

Inan3 said:
Imagine this....Warriors going to battle, full of anger and hatred, ready to kill, destroy and conqueor and THEN...the opposing side breaks down and cries , so the other side stops...drops their weapons and gives them a great big hug! NOT!!!!!!!
Do you suppose that anyone cried during the holicaust? But they were still massacred! Do you think POW's may have cried? or children or women being abused and killed? Need I say more?

If crying was sufficient on its own to save lives, we would all be cry babies and there would be no war.
Good chance there would be humans as well, as we would have struggled to avoid any kind of predation.
Similarly, if we had stopped to pray when a predator approached, there would likely be no humans left.

Inan3 said:
As to the primitives it was survival of the fittest not the weakest. Unfortunately it still is.

i thought you refuted evolution?

Nathan45 · Sep 29, 2007

This post reminds me of a a very cool wiki article I read the other day about emotions relating to the sense of smell... ( of course this is pretty loopy and totally hypothetical, the wiki isn't very well sourced, but still interesting )

http://en.wikipedia.org/wiki/Emotion

Primary emotions

Click to expand...

(i.e., innate emotions, such as fear) "depend on limbic system circuitry," with the amygdala and anterior cingulate gyrus being "key players".

Smell carries directly to limbic areas of the mammalian brain via nerves running from the olfactory bulbs to the septum, amygdala, and hippocampus. In the acquatic brain, olfaction was critical for detecting food, foes, and mates from a distance in murky waters.

An emotional feeling, like an aroma, has a volatile or "thin-skinned" quality because sensory cells lie on the exposed exterior of the olfactory epithelium (i.e., on the bodily surface itself).

A sudden scent, like a whiff of smelling salts, may jolt the mind. The force of a mood is reminiscent of a smell's intensity (e.g., soft and gentle, pungent, or overpowering), and similarly permeates and fades as well. The design of emotion cues, in tandem with the forebrain's olfactory prehistory, suggests that the sense of smell is the neurological model for our emotions.

Presumably, before the mammalian brain, life in the non-verbal world was automatic, preconscious, and predictable. The motor centers of reptiles react to sensory cues of vision, sound, touch, chemical, gravity, and motion with pre-set body movements and programmed postures. With the arrival of night-active mammals, circa 180 million years ago, smell replaced vision as the dominant sense, and a different way of responding arose from the olfactory sense, which is proposed to have developed into mammalian emotion and emotional memory. In the Jurassic Period, the mammalian brain invested heavily in olfaction to succeed at night as reptiles slept one explanation for why olfactory lobes in mammalian brains are proportionally larger than in the reptiles. These odor pathways gradually formed the neural blueprint for what was later to become our limbic brain.

Like aromas, emotions are experienced as either positive or negative, pleasant or unpleasant; emotions do not seem to be neutral. Like odors, feelings come and go, but are logical, and clearly show upon our face in mood signs. It is likely that many emotions evolved from aroma paleocircuits a. in subcortical nuclei (e.g., the paleocortex of the amygdala), and b. in layers of nerve cells within the forebrain's outer covering of neocortex. The latter's stratified architecture resembles that of the olfactory bulb, which is organized in layers as well.

Interestingly enough, crying is also often triggered by strange smells, like onions, etc.

The Evolution of Tears

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