The invention of tear ducts


Research Submarine Asherah

Designer was riding Her submarine through the depths of the ocean one day, taking stock of Her work, and decided, “I’ve learned just about everything I’m ever going to learn from these prototypes. It’s high time to take the next big step toward the ultimate goal, a species of animal in which to ripen souls for harvest.” (Of course, souls that turn out goatlike go to Hell, to suffer eternal torment at the hands of Satan, and souls that turn out sheeplike go to Heaven, to kowtow forever at the feet of God. But Designer had to come up with something considerably more sophisticated than sheep and goats, to satisfy God’s requirement that the Fate of Souls be contingent instead of determined.)

Now, if Designer had done a complete redesign, when advancing from aquatic to terrestrial organisms, Hell might well have frozen over before there were any goatlike souls to fuel the flames. So Designer said, “I know that the optics are different in air than in water, but fish eyes are gonna have to do.”Gray896
Lacrimal system
After observing that Her transitional prototype frequently took dips in the marsh to wash its eyes, She invented an organ to wet the eyes with saltwater. Compared to the eyes themselves, the lacrimal glands were a cinch to get right. As for eyelids, Designer had already tested them on some sharks. She did not anticipate that drainage would be a problem, but found that mammals with drops of water running down their faces looked very sad. In a flash of brilliance, Designer realized that eyewash could be reused to moisten the nostrils. And that was when She invented the lacrimal and naso-lacrimal ducts. What initially was supposed to be an aesthetic feature turned out to serve a useful function. God was highly impressed, and gave Designer, whom He called Asherah, a generous bonus at Christmas.

Ajrud

“Yahweh [front, flaunting large penis] and His Asherah [rear, working at computer]”

155 thoughts on “The invention of tear ducts

  1. phoodoo:

    “The earliest mammals were generally small animals, probably nocturnal insectivores. This suggests a plausible evolutionary mechanism driving the change; for with these small bones in the middle ear, a mammal has extended its range of hearing for higher-pitched sounds which would improve the detection of insects in the dark.[23] Natural selection would account for the success of this feature.

    There is still one more connection with another part of biology: genetics suggests a mechanism for this transition, the kind of major change of function seen elsewhere in the world of life being studied by evolutionary developmental biology.[8]” – Wikipedia

    Phoodoo: Ignoring the fact that the last paragraph is almost a complete non-sequitor, what does it mean that because better hearing would be beneficial for small mammals in the dark, that this is a mechanism for how it came to be?

    I don’t think that’s what that paragraph is intended to convey. Though I would certainly agree that paragraph could have been much more clear. But my guess from the keywords “genetics suggests a mechanism” and “evolutionary developmental biology” they’re thinking of mutations in gene-regulatory networks that are responsible for the particulars of embryological development. That’s also what you find in the reference given in [8].

  2. phoodoo,

    Preliminary brief comment (don’t know when I’ll have more time to spend here): When I throw in a quick link to Wikipedia, you should not assume that it’s all I know about the topic. Back in 2010, I made some comments about the evolution of the ossicles in a public talk I gave, having done enough reading on the topic to be pretty sure I was getting things right. If I had gone into the topic here, I’d have done some more reading, not only to refresh my memory, but also to see if the scientific consensus had changed.

  3. phoodoo: How could you ever demonstrate that? That is the point. You can’t.

    Why not? Why shouldn’t I be able to measure speed? Or strength? Or survival? Or number of offspring? Or any trait one might be interested in?

    Of course you can. Already been done, most likely.

  4. phoodoo: How could you ever demonstrate that? That is the point. You can’t.

    Your inability to figure out how is not an indication that it can’t be done.

  5. Corneel: Agreed, we went over this thoroughly not too long ago.

    I probably missed that one, having been otherwise occupied for most of the year. But I’ve seen that clueless misinterpretation of the concept of fitness far too many times for sanity.

  6. Curiously, it seems taken for granted by Design enthusiasts that every last feature has a benefit, even if presently cryptic. Otherwise it would disappear (through evolution, we can gleefully note!)

    Despite phoodoo’s bovine insistence, this is not in fact the stance taken by evolutionists. Mere presence is not enough to allow inference of benefit. ie, completely the wrong way round.

  7. Tom English:

    CharlieM: What we see is the general form radiating into specialist forms. It happens in the formation of tear ducts, in the formation of limbs as Rumraket has already stated, in the branching of species, and throughout the evolution of life as a whole.
    This pattern repeats at all levels, the whole is repeated in the parts. There is much wisdom in the phrase, “as above, so below.”

    We know and can see the direction inherent in individual development because the time frame allows us to see examples of the whole process, the birth, development, maturity and death of individual organisms. It is more difficult to see the direction inherent in the process of evolution because from our limited existence we do not get the same clear picture of the whole process.

    But if we take the whole to be reflected in the parts as genuine, as I do, then the evolution of life on earth is in the midst of undergoing the same process of birth, development, maturity and death. As Tom wrote, “we do witness an evolutionary process in embryogenesis.”

    To see the world in a grain of sand, evolution in a tear duct

    Charlie, I have to give you credit here for a well-thought-out and articulate comment. I don’t see the sublime plan that you’re seeing in embryogenesis — for instance, the non-bony part of the tails that humans grow as embryos simply dies (when things go right), rather than turns into something else — and I of course do not see any directedness in evolution of lineages, apart from that of natural selection. But what you’re saying is sane, and even poetic. Most importantly, it strikes me as an honest expression of your belief.

    Thank you Tom. I don’t think of embryogenesis as the unfolding of a sublime plan. What I do see is the individual expression of Goethe’s typus. I was pleasantly surprised by the, in my view, unbiased Wikipedia entry on ‘Goethean Science’ What I do see is that the evolution of life is also an evolution of consciousness.
    The fact that we all possessed tails during our development would suggest to me that tails were part of our evolutionary history. And as I believe that our evolution included a fish like stage, a tail would be as useful then as legs are today.

    I don’t know how to fault people who believe, on faith, that natural selection is actually divine guidance of the course of nature. However, arguments that science actually favors belief in invisible guidance of evolution are not a matter of faith. They reveal a failure of faith.

    To me natural selection is just a phrase for natural feedback similar to an aircraft’s stability augmentation system. The path taken isn’t pre-determined but it is buffered against environmental fluctuations. In other words not a creative force but a stabilising force.

    I need to say from time to time that what animates me in my opposition to ID is not opposition to religion, but instead opposition to attempts to insinuate religious beliefs into public science education. Growing up Southern Baptist, in the Sixties and early Seventies, I was taught that the two-way wall of separation of church and state was the best guarantor of religious freedom for all. I was not taught to see it as an application of the Golden Rule, but I always saw it that way, and continue to see it that way today. Christians ought, if they believe what they say that they believe, to recognize that they should not press their majoritarian religious beliefs on minorities, even as they recognize that they would not want to have majoritarian religious beliefs pressed on them and their children, were they in the minority.

    We are in agreement here. IMO religion is a personal affair in which everyone should be free to follow their beliefs without outside interference (obviously so long as they remain within the law if acting on those beliefs), neither imposed by parents or by culture. Science, on the other hand, should give us knowledge which is universal and so the same for everyone.

  8. Corneel: Why not? Why shouldn’t I be able to measure speed? Or strength? Or survival? Or number of offspring? Or any trait one might be interested in?

    Of course you can. Already been done, most likely.

    So let me get this straight. We take a group of koalas, and we give them say, a forty yard dash test. We record the results and then compare them with the number of offspring those koalas have had. Then we can know if speed is adaptive or not.

    Then we take a bunch of peacocks, give them some mini barbells, so how many curls each can do, then compare how many kids they have as well.

    Then we take some llamas, hide some food behind a series of mazes, and locked door puzzles, and see which llamas can figure out how to get the doors open. Then compare the results with how many offspring the smart and the dumb llamas get. Bingo we got our answer. Is smart adaptive or not.

    I just have one question. When we give the peacocks the barbells, do we measure how many reps, or who can curl the biggest one? Because, one might be able to do ten curls with a three pound dumbbell, but is useless with the five pound one, while another maxes out his reps really quick, but can still do one with the five.

    I sure hope these tests have already been done, because I really want to know if strength is an adaptive trait or not.

  9. phoodoo: I sure hope these tests have already been done, because I really want to know if strength is an adaptive trait or not.

    Certainly is in chimps. Chimps show much more sexual dimorphism than bonobos.

  10. Alan Fox: phoodoo: I sure hope these tests have already been done, because I really want to know if strength is an adaptive trait or not.

    Certainly is in chimps. Chimps show much more sexual dimorphism than bonobos.

    How would you know? By intuition?

    And can it be an adaptive trait in some animals and not in others, if they are related? First it was non-adaptive, like say in the small mammal line, then became adaptive later, than became non-adaptive again?

    And if I want to know who the strongest females are, all I have to do is measure how many babies they have, and the ones who had the most babies are of course going to be the strongest. And likewise, speed must not be adaptive, unless, it just so happens, that the strongest ones are also the fastest. And the smartest?

  11. phoodoo: How would you know?By intuition?

    No, by observation. Although bonobos have not been as extensively studied in the field as chimps, morphological and behavioural differnces are pretty clear – and might even be so to you, if you’d care to glance at some of the material available on line. Here is something for you to scoff at, you incurious person, you!

    And can it be an adaptive trait in some animals and not in others, if they are related? First it was non-adaptive, like say in the small mammal line, then became adaptive later, than became non-adaptive again?

    How many times! Adaptation involves populations, not individuals. Individuals do not evolve, though they develop from a single egg that may grow into sexually reproducing adults and leave offspring.

    And if I want to know who the strongest females are, all I have to do is measure how many babies they have, and the ones who had the most babies are of course going to be the strongest. And likewise, speed must not be adaptive, unless, it just so happens, that the strongest ones are also the fastest. And the smartest?

    Life is diverse. There are many ways of making a living. In chimp society, being a weak male is not a recipe for success. In bonobo society, aggression is dealt with by female solidarity, sexy males do better than aggressive ones. I may have mentioned the niche before. There is feedback between a population of organisms and the niche they occupy.

    Swimming ability is not much use to naked mole rats.

  12. Alan Fox,

    By observation huh? I see.

    Well, I have observed that luck is the biggest factor in what organisms mate. So I guess, we can conclude that its not smarts, its not strength, its not speed, its luck. So if luck is the most important factor, there is no way strength could be adaptive.

  13. Here is an intersesting paper on the human nasolacrimal ducts.

    From the OP:

    Designer realized that eyewash could be reused to moisten the nostrils. And that was when She invented the lacrimal and naso-lacrimal ducts. What initially was supposed to be an aesthetic feature turned out to serve a useful function.

    A more detailed study shows that this witty story belies a superficial (mis)understanding of the nasolacrimal system. This system has always served a useful function. It allows for the contents of tears to be reabsorbed and it provides a feedback system to ensure that the eyes are constantly bathed in a protective film. These ducts allow for recycling and regulation.

    Also from the abstract:

    The wall of the lacrimal sac and the nasolacrimal duct are made up of a helical system of different connective tissue fibres. Wide luminal vascular plexus are embedded in this helical system, which is comparable to a cavernous body. Caudally, the vascular system is connected to the cavernous body of the inferior turbinate. With distension the system may be “wrung out” due to its medial attachment and helically arranged fibrillar structures. Thereby, tear fluid is drained distally. The embedded blood vessels underlie vegetative control. By means of this innervation, the specialised blood vessels permit regulation of blood flow by opening and closing the lumen of the lacrimal passage as effected by the engorgement and subsidence of the cavernous body, at the same time regulating tear outflow.

    Notice the similarity to the heart which also employs a similar ‘wringing out’ due to the helically arranged muscle fibres. The whole reflected in the parts.

    I know that the OP did not intended for this to be taken too seriously. But if it prompts us to have a closer look at the system then we can learn a lot about the wisdom inherent in living systems.

  14. phoodoo: I just have one question. When we give the peacocks the barbells, do we measure how many reps, or who can curl the biggest one? Because, one might be able to do ten curls with a three pound dumbbell, but is useless with the five pound one, while another maxes out his reps really quick, but can still do one with the five.

    I sure hope these tests have already been done, because I really want to know if strength is an adaptive trait or not.

    There is a whole industry

    “WOD Toys Barbell Mini – Promotes safe, playful fitness participation and so much fun, and the ability to test adaptive traits!

    Now your kids and peacocks can join in the fun of overhead squats, cleans, & all those lifts you love to do ,all the while testing their adaptive traits.

    Includes 1 Mini Barbell, 4 Mini Bumper Plates and 2 Mini Collars
    2.2 pounds, 3 feet long, 7 inches high. For 3+ years of age.

    Optional wing adapters for peacocks available.”

  15. newton,

    Have you ever watched peacock bowling? What a hoot.

    Even though they can never hit the pins, their ineptitude is a sexually selected for advantage. The thinking is, being that uncoordinated, they must be good at other things, like raising peacocks.

  16. CharlieM: closing the lumen of the lacrimal passage

    Another accident, that just so happen to cause an advantage and increase in re-productivity!

    In their niche this was important.

    If you were to actually count the number of things in our ancestors which were an advantage and increased reproductivity, well, let’s just say its a good thing the amount of counting number is infinite.

  17. phoodoo: If you were to actually count the number of things in our ancestors which were an advantage and increased reproductivity, well, let’s just say its a good thing the amount of counting number is infinite.

    And of course it is not just the evolution of eye itself in isolation that has to be taken into account. As we have seen the tear system is vital for the functioning of vision in land vertebrates, the eye and nervous system have to be coordinated, the living parts of the eye have to have an adequate blood supply, two eyes are needed for binocular vision and all the muscles needed for eye movement, lens focussing and pupil dilation and constriction have to be attached in the appropriate positions. I’m sure there are more requirements that I haven’t thought of.

  18. Allan Miller:
    CharlieM,

    … and yet …

    Good point. Originally I did write, “the tear system is vital for the functioning of vision in all land vertebrates”, but I deleted the ‘all’ because I didn’t know if what I was saying was true or not.

    But anyway, from your link:

    No matter how many carrots a rabbit eats, he’s always going to be prone to eye problems. A rabbit’s lack of tear ducts makes him high-risk for bacterial infections, eye abnormalities, dry eyes and eye traumas, such as cornea scratches.

    Although from here

    As rabbits have only one tear duct — located very close to the tooth and gums — the duct can be easily blocked due to oral disease (longtooth impaction is also very common in rabbits). Epiphora may occur also due to longstanding respiratory disorders that block the nasal passages.

    So I think it needs further research before deciding which is true.

    Anyway, with or without tear ducts I still think that these animals produce tears. And I would have thought that if any type of animal was to have an advantage by having an efficient tear system it would be rabbits with their lifestyle which involves running through undergrowth and digging in dirt and dust.

    So if rabbits can get away with less efficient or no tear ducts, why can’t we? This is a lack of an adaptation that hasn’t stopped them being very successful at producing descendants. Even with the likes of myxomatosis, and if you have ever seen a rabbit with myxomatosis its eyes are not a pretty sight.

  19. CharlieM,

    Why does everything have to be universal? Why don’t we have long ears and a cotton tail, and eat our faeces? The main point is, your contention on essentiality is refuted. It’s also interesting that seals and whales lack them. Probably something to do with the aquatic lifestyle rendering them unnecessary, if I may be permitted a ‘just-so story’.

  20. Allan Miller:
    CharlieM,

    Why does everything have to be universal? Why don’t we have long ears and a cotton tail, and eat our faeces? The main point is, your contention on essentiality is refuted. It’s also interesting that seals and whales lack them. Probably something to do with the aquatic lifestyle rendering them unnecessary, if I may be permitted a ‘just-so story’.

    If you want me to answer you will have to provide a reference or quote from where I claimed everything has to be universal or essential.

  21. phoodoo: Have you ever watched peacock bowling? What a hoot.

    No

    Two questions:
    Aren’t the feathers an issue when you roll the peacock down the alley and where does the bowler put his fingers?

    Even though they can never hit the pins,

    I think that would be on the bowler not the peacock.

    their ineptitude is a sexually selected for advantage.

    After a few frames , I doubt the peacock would be able to reproduce no matter how sexually appealing it might be.

    The thinking is, being that uncoordinated, they must be good at other things, like raising peacocks.

    So I gather

    “Nowadays peacock farming is considered as a profitable poultry farming business. You can raise peacock commercially in both rural and urban areas. Peacock farming can play an important role for reducing unemployment problem and help to create a new way of earnings. And commercial peacock farming business can help to develop the socioeconomic condition of a country or nation.”

  22. CharlieM: If you want me to answer you will have to provide a reference or quote from where I claimed everything has to be universal or essential.

    ‘If rabbits can get away without tear ducts, why can’t we’. This implies that what holds for one species should hold for all.

  23. Allan Miller:

    CharlieM: If you want me to answer you will have to provide a reference or quote from where I claimed everything has to be universal or essential.

    ‘If rabbits can get away without tear ducts, why can’t we’. This implies that what holds for one species should hold for all.

    What I was getting at is that it is purported to be an adaptive feature that confers an advantage to humans, why has the same not happened in the case of rabbits?

    So what do you think I contended on essentiality?

  24. CharlieM: What I was getting at is that [having a tear duct] is purported to be an adaptive feature that confers an advantage to humans

    The reverse situation is at least mildly debilitating, resulting in sore eyes, increased likelihood of infection, blurred vision.

  25. Alan Fox: The reverse situation is at least mildly debilitating, resulting in sore eyes, increased likelihood of infection, blurred vision.

    The more I look into the tear system the smarter it is revealed to be. Here for example:

    Interestingly enough, different types of tears have very unique chemical compositions in humans: basal tears (the normal tear film) and reflex tears are full of anti-bacterial enzymes and anti-oxidants; whereas emotionally-triggered tears contain high levels of protein-based hormones, including the precursor to cortisol and one that functions as a natural painkiller.
    The liquid that covers the eye during the normal course of a day isn’t just a simple layer of basal tears, however. The human eye’s “tear film” is actually comprised of three different layers, each of which is produced by a unique gland in the eye area. The mucous layer sits directly on the surface of the eyeball and is made up of a gel-like proteins called mucins, which are secreted by little glands on the inside of the eyelids. Because it is hydrophillic (water-attracting) it helps promote even dispersal of the tear liquid across the eye.
    The aqueous layer sits on top of the mucous layer , in the middle of the tear film, and is comprised of the basal tears discussed earlier. On the outer-most surface of the tear film is the lipid layer, which is made up of oils secreted by glands on the rim of the eyelids. The hydro-phobic secretions of the lipid layer, called meibum, coat the aqueous layer and keeps it from evaporating or spilling out before it reaches the drainage channels in the inner corner of the eye.

    Very clever stuff.

  26. Alan Fox:
    Are we sure rabbits don’t have tear ducts?

    I think there has been a bit of confusion between nasolacrimal ducts and the ducts from the lacrimal glands feeding the eyeball.

  27. Allan Miller:
    CharlieM:

    “As we have seen the tear system is vital … [etc] ”

    I wrote

    As we have seen the tear system is vital for the functioning of vision in land vertebrates

    Can you explain why this is not a correct statement?

  28. CharlieM: You must be Googling the the stuff that I am

    Haha yep. Interesting snippet on the preorbital gland, a scent gland of deer considered homologous to the lacrimal gland. Deer have numerous scent glands. I bet most or all are homologous with other structures having somewhat different functions. Evolutionarily, this would seem an example of co-option. But ID seems to have to force fit itself in here, usually by way of some poor analogy or other. Why not just have tear glands and scent glands?

  29. Allan Miller: Haha yep. Interesting snippet on the preorbital gland, a scent gland of deer considered homologous to the lacrimal gland. Deer have numerous scent glands. I bet most or all are homologous with other structures having somewhat different functions. Evolutionarily, this would seem an example of co-option. But ID seems to have to force fit itself in here, usually by way of some poor analogy or other. Why not just have tear glands and scent glands?

    Here we have an example of a general system being adapted for a specialist use. Just as animals such as whales use the general form of the pentadactyl limb for a specialist purpose.

  30. CharlieM: Here we have an example of a general system being adapted for a specialist use.

    And why can’t evolution do that?

  31. Allan Miller: And why can’t evolution do that?

    I can and it does. Animals evolve in a one-sided specialist way according to their nature and habits. Of course the more specialised they become the less likely they are to evolve further.

  32. newton:

    CharlieM: Accidentally on purpose 🙂

    Whose purpose and why?

    It was a light-hearted remark. But I was just contemplating the fact that lacrimal glands, ducts, composition of the films over the eyes and the associated blood vessels, nerves and muscles all work together for the purpose of keeping the eyes in good condition.

    Speculating about some external designer building organisms in way similar to human designers is not something that I would contemplate.

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