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Christopher Halliwell

Secondary Education Physics, Mississippi State University

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What is the advantage of evolving the ability to cry?

Is it simply a result of evolving the ability for complex emotions?


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  • Mar 21 2013: there is a lot of evidence that many of our physiological responses (blushing etc) are social signals, and i'd be surprised if crying wasn't naturally selected for the same reason. the spoken word came relatively late in our evolution, and so mournful cries and watering eyes would be a good cue to family members to provide comfort from either physical or emotional pain. sympathy and mutual assistance being important facets of our ability to survive and thrive.
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      Mar 21 2013: Expression of emotion plays largely in the social intelligence of humans. Bottomline: crying has many different functions , so that means the ability to cry isnt simple. It is very hard to comprehend humans losing tear glands anytime soon, unless we evolve into emotionless, electronic, metalloid robots!(they wouldnt have use for tear glands!) Therefore, the adaptation of the ability to cry is crucial for humans evolution and reign over Earth.
      • Mar 21 2013: not necessarily. it might have once been simple, but we now have many uses for it as our social structures have evolved along with our physical structures. we could lose tear glands if something more useful ever came along. they're not crucial, but they help, which is why they survive as a trait.
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      Mar 21 2013: Our ability to rationalize things is truly amazing. We can find a purpose for anything we see. When we need to kill a mammoth and use stones for that purpose, we may start believing that killing mammoths is the purpose of stones. Well, that was OUR purpose for them.

      Why can't we signal grief and comfort each other by rubbing our noses together? Why cries and tears?
      • Mar 21 2013: because rubbing noses takes a conscious effort, it is an action not a signal. anyway that argument doesn't work because it could have been something other than cries and tears. it doesn't have to be tears, but something is beneficial, so when that something comes about, it is naturally selected for.

        also your example is not of rationality. if we were rationalizing the existence of stones we'd see that they aren't 'for' anything until we give them a purpose. deciding that stones must be for killing mammoths is the exact opposite of rational thought!
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          Mar 21 2013: Re: "also your example is not of rationality. if we were rationalizing the existence of stones we'd see that they aren't 'for' anything until we give them a purpose. deciding that stones must be for killing mammoths is the exact opposite of rational thought!"

          With that said, substitute "stones" for "tears" and "killing mammoths" for "expressing emotions".
      • Mar 21 2013: you've skipped the rational part again. many studies have shown the importance of outward behaviors such as flushed cheeks, and many more have shown the importance of social structure in the evolution of human society (do you debate either of these points?) it's not a leap at all to conclude that tears likely are another part of this, that they are useful to society and individuals within that society. there's a pattern there, you don't have to 'try' to rationalize anything.

        there is no evidence that stones evolved, nor any precedent nor similarities, however there is a lot of evidence that human physiological responses have evolved, many precedents that lead me to suggest this conclusion (facial expressions, growls etc to name but 2 more) all of which are similar - a human physiological response to stimuli.

        by your own argument, we could not possibly conclude that lack of air in a tyre is the cause of poor vehicle handling! utter nonsense to dismiss something out of hand because you personally declare it to be unknown.
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          Mar 21 2013: Let's step back. It's impossible to establish by means of reasoning what is reasonable and what is not. This part of the argument is silly.

          You seem to say that people cry with tears to signal emotions to other people. Signaling emotions to each other plays important role for social survival. Therefore, crying with tears to signal emotions is justified for evolutionary purposes. Right?

          While signaling emotions is important, it is unclear why crying with tears is a suitable or the best way to do that.

          Blushing can be explained by hormones produced as a result of emotion affecting blood circulation and breathing. Blushing may serve as a signal of emotion because of the connection between emotion and blushing. But, in my opinion, it is incorrect to say that "people blush to signal emotions".

          Similarly, people may cry as a result of emotion because certain emotions may, for instance, happen to excite areas in our brain responsible for secretion of tears. Just as with blushing, I don't think crying has a purpose of signaling emotion, because crying is not the only and not the best way of signaling emotions. It is used for this purpose like the stone is used to kill a mammoth, but, in my opinion, it has not "evolved" for this purpose nor it is caused by our need to signal emotions.

          I hope, you find this reasonable.
      • Mar 22 2013: yes it is, and that's the flaw with your own cognitive process that's leading you to dismiss evidence.

        it is a suitable way to do that, as evidenced by thousands of years of human social life. i didn't say it was the best way, it's just the way that evolved and it does the job.

        your opinion is wrong, but that's understandable because you are again looking at only one point. there are many purposes of blushing and flushing, one of them (and only one of many) is just as you said, another one of them is a sexual signal, useful for a pre-verbal human.

        again i didn't say crying was the only way, i said it clearly has a purpose which it achieves. we could possibly have developed other ways, some of them could be better, but this is what happened to evolve and it works so it remains part of human physiology. it is not in any way similar to how a stone is used to kill a mammoth. crying is innate while throwing a stone is not (we have to think about it and choose to do it), crying is a reaction while throwing a stone is not, just to give two.

        indeed it has not evolved for any purpose at all, that's not what evolution is about. new traits come up, and if they are useful they get kept, that's all. a likely scenario is one day a human was the first to cry. it provoked a response from members of the group who rendered assistance, increasing the chance that that human would survive and bear children who would also cry when they were upset. that's not my opinion, that's a conclusion drawn from evidence.

        i think this question might help you understand: why did we evolve fingers?
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          Mar 22 2013: This was a great discussion. I finally have to completely agree with you. I had doubts regarding "survival of the fittest" principle being a tautology paraphrased as "survival of the survivors". This article explains it. http://www.talkorigins.org/faqs/evolphil/tautology_org_ver.html. It doesn't appear to be a tautology if we speak of specific adaptations, because "fittest" isn't defined as just "survivors" but is defined through specific traits in every specific case. The argument isn't obviously invalid as it was supported by Karl Popper among others.

          However, why we signal emotions through crying and not by other means is a more complex question as noted at the end of the article:

          "In order to explain why a species exhibits this trait rather than that trait, you need to know what the null hypothesis is (otherwise you can make a selective explanation for both a case and its opposite equally well). Perhaps it has this trait because its ancestors had it and it has been maintained by selection. Perhaps it has it because it would be too disruptive of the entire genome and developmental machinery to remove it. Perhaps it has it for reasons to do with genetic drift, simple accident, or whatever. In order to make a good scientific explanation, says Griffiths, you must know a fair bit about the phylogeny of the species, its environmental distribution, and how the processes that create the trait work at the level of genes, cells and zygotes.

          This leads us to the question of what a scientific explanation really is; indeed, it opens up the question of what science is, that it is so different from other intellectual pursuits like backgammon, theology or literary criticism."

          And the article regarding falsifiability of evolution was also a good read: http://www.talkorigins.org/faqs/evolphil/falsify.html. It appears that scientific theories do not have to be falsifiable to be scientific. Which still leaves me puzzled over what science is. The article is open-ended.
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          Mar 22 2013: Re: "there are many purposes of blushing and flushing"

          Perhaps, it's better to say "functions", not "purposes". Language is quite important as we speak of evolution. It often creates an illusion that we imply volition in nature. Here is Darwin on this issue:

          "Others have objected that the term selection implies conscious choice in the animals which become modified; and it has even been urged that, as plants have no volition, natural selection is not applicable to them! In the literal sense of the word, no doubt, natural selection is a misnomer; but who ever objected to chemists speaking of the elective affinities of the various elements?—and yet an acid cannot strictly be said to elect the base with which it will in preference combine. It has been said that I speak of natural selection as an active power or Deity; but who objects to an author speaking of the attraction of gravity as ruling the movements of the planets? Every one knows what is meant and is implied by such metaphorical expressions; and they are almost necessary for brevity. So again it is difficult to avoid personifying the word Nature; but I mean by Nature, only the aggregate action and product of many natural laws, and by laws the sequence of events as ascertained by us."


          This is what causes my eyebrows raise in the phrase "our emotions are programmed by evolution."

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