Average Animal Size vs Time

Discussion in 'Biology & Genetics' started by EndLightEnd, Nov 8, 2008.

  1. DaveC426913 Valued Senior Member

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    Sorry, isn't the theory predicated on the Earth shrinking?
     
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  3. Scott Myers Newbie Registered Senior Member

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    You mean the one from the guy I was sharing? Of course not. He eliminates it in his possibilities, though all bodies will compress and settle won't they? Rough gathering of rocks and ruble piled up till there is enough to create a molten core, taking out all the air gaps etc. That is what we say happens. But no, to be direct, the idea of having higher pressures has nothing to do with that idea, or an increased gravity idea. The idea is that there was just more atmosphere. There is no reason at all this is unreasonable.
     
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  5. DaveC426913 Valued Senior Member

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    No one doubts that the proto-body that coalesced into Earth was once a diffuse mass of dust, rocks and gas. But it would be quite a stretch posit that the Earth changed size much after the end of the first era*.
    Those are two very different stages.

    *excluding atmospheric loss and bombardment, of course.

    Anyway, I'm not really motivated to read all the chapters at the link. Not really the way we do things here. Normally, you would pick an assertion or two and argue it here, using your reference material.
     
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  7. Scott Myers Newbie Registered Senior Member

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    I offered a link to anyone interested in following my ideas to the fullest argument, mostly because I learned that his ideas are more fully developed. You would not need to read "all the chapters at the link", to have read that I already explained that a changing gravity is NOT really in consideration by myself, or the author of the website I cited. It would be prudent to follow along with the thread, so that you know what has been posited and why I shared the link in the first place, let alone have me repeat that a shrinking planet and extra gravity is NOT likely. Chapter 4 is the only relevant chapter anyhow, but then you didn't read where I stated that either I suppose. I could care less what you are motivated to read since you have decided to go ahead and fix my wayward ways here on the SciForums. lol

    What you are saying is the proper way to "do things here", is pretty much exactly what I have done. Why don't you go back and read what the idea is so you understand it and can join in and then make some kind of comment related to the subject of what I introduced, instead of criticizing how I am presenting my arguments. It kind of evolved slightly along the way here since I first posted, but my initial idea has not changed and is only one or two points just as you have assigned.

    Q) The only truly gargantuan vertebrates under our current environment remain in the ocean. What was so different, or changed to make this no longer possible? Along with the potential plant loss during a major impact event like Chicxulub causing world wide food shortages; what else might have been different to support such massive creatures?


    A-1) Higher O2 levels likely helped insects and dinosaurs grow bigger.
    A-2) Higher atmospheric pressure, however, is more likely to have a greater effect on both insect size and dino size. 200 Atmospheres seems to be what is required to have the desired effect to the degree it is needed.

    A-3) Other factors, or all of the above and then some others? Probably also true
     
  8. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    Why do you assume it is no longer possible?
    15000 years ago mammals were much larger than today, do you assume that the atmospheric pressure was much higher?
    African elephants are about the same weight as hadrosaurs. There existed mammals that were as large as Trex.
    It seems the only truly unusually large dinosaurs were sauropods. The largest whales are more than twice as heavy as the heaviest sauropods. I don't think there is any reason to come up with absurd ideas to explain dinosaur sizes.

    Probably.

    Uh, no. Are you seriously proposing that the atmospheric pressure was higher than the pressure found on the ocean floor 1 mile down?

    I recommended putting down the bong and picking up a book.
     
  9. Scott Myers Newbie Registered Senior Member

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    "Why do you assume it is no longer possible?"

    I assume nothing. There are none. There's a clue. What happened to make them go away? There are reasons what are all of the reasons? There are major problems supporting the size of some of the large creatures we have found under current atmospheric pressures. With a considerable increase in pressures, this becomes much easier. Are you familiar with the Square-Cube law and what that means to creature size, muscle mass & blood flow requirements? It's a serious problem with making creatures larger. There are other issues, but most blaring is, there aren't any land dwellers larger than elephants and they need help standing up.

    "It seems the only truly unusually large dinosaurs were sauropods. The largest whales are more than twice as heavy as the heaviest sauropods. I don't think there is any reason to come up with absurd ideas to explain dinosaur sizes."


    Correct, and whales collapse on shore obviously. You can't use ocean creature size to associate that with land dwellers. The extreme size of ocean creatures obviously is what lead me, and a few other folks in the world, to look at pressure as a potential mechanism to explain.

    A-1 O2 levels helping grow insects and dinos bigger. Yes it can help, but to what degree. Did you read back to where I found a fruit fly study where they added the extra pressure that would have been there due to O2 being heavier with higher percentage of O2? Well, in a few generations the fruit flies almost doubled. O2 is good, but not enough to deal with the physiological questions of size vs volume, blood flow supply and weakening muscular strength with size. Rabbits, small mammals, etc can jump several times their body weight. Rhinos can run and gallop. Elephants? They can't have more than two feet off the ground. There are limits to size and there must have been reasons beyond running out of green food. I say.

    "Uh, no. Are you seriously proposing that the atmospheric pressure was higher than the pressure found on the ocean floor 1 mile down?

    I recommended putting down the bong and picking up a book."

    I'm proposing this as a possibility. Please find in your books (because I don't know how to read, only puff puff) why this is an issue. O2 does not liquefy at ambient Earth temperatures, Venus holds over 90 atmospheres at ground elevations, Just as an example locally. Liquid and gas dynamics are a bit different, so you can't imagine that the same pressure in either is equal for one thing.

    What are your physical/chemical or otherwise reasons that this could not have been?
     
  10. Write4U Valued Senior Member

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    I believe this establishes a size and weight limit of surviving species after the K-T extinction.
    https://en.wikipedia.org/wiki/Cretaceous–Paleogene_extinction_event
     
  11. Scott Myers Newbie Registered Senior Member

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    As such, this certainly explains that the entire ecosystem went through as reset, and oddly enough, dinosaurs of all sizes died out and lost to the mammal kingdom it would seem. What is odd is how even the small dinos also disappeared almost completely. Surely environmental stresses and lack of food (plant life) played a huge part in resetting the playing field. Always wondered what else might be contributing to the relative smallness of even similar species from 65 million years ago to now.
     
  12. Write4U Valued Senior Member

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    You may be too pessimistic about this.
    There is an abundance of descendants from small dinosaurs all around us. Lack of fossil remains does not prove lack of existence.

    Here is an example of a species that survived the extinction event.

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    Living fossil
    The coelacanths were thought to have gone extinct 66 million years ago, until a living specimen belonging to the order was discovered in 1938.

    But it seems that all birds are also descendant from dinos.
    Which yields an interesting perspective on evolution.
    IMO, most evolutionary changes do not become readily apparent until we find a modern species 60 million years later which is genetically very closely related to now extinct precursors.

    That birds are descendants from dinos is obviously related to the ability to fly and travel long distances in relatively short times, a trick the insect had already discovered a few hundred million years earlier.

    It affords a clear survival advantage as is evident of small flying reptiles surviving today as well as an incredible variety of insects
    https://askabiologist.asu.edu/questions/birds-dinosaurs-reptiles

    We still have a part of the human brain that is reptilian in origin........

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    Last edited: Jan 2, 2019
  13. Write4U Valued Senior Member

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    The K-T extinction event is reported to have killed all animal life over 25 kg. I am sure this is an educated guess, but may be used as a baseline.
    https://www.amnh.org/exhibitions/di...ls-new-discoveries/extinction/mass-extinction

    However, long before that.
    About; The Paleozoic Periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian

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    The Cambrian truly is an astonishing period in evolution of life on earth.
    http://www.fossilmuseum.net/Paleobiology/Paleozoic_paleobiology.htm

    Permian Period (286 to 245 mya)

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    Note size of skeleton.

    http://www.fossilmuseum.net/Paleobiology/Paleozoic_paleobiology.htm#PermianPeriod
     
    Last edited: Jan 3, 2019
  14. Scott Myers Newbie Registered Senior Member

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    Write4U,

    Thanks for all the good info. I appreciate it. I have done some little bits of homework for the antithesis, and well, there are much larger mammals since the Chicxulub event that were around mush more recently. I would think the next step logically would be to further study what might be the current physical limitations in size (scale) and why. I think the limit lies somewhere between the giganatosaurusesesesese, and the giant tusked and trunked beasts that walked the Earth tens of thousands of years ago instead of tens of millions of years ago. Certainly this is a combination of physiological limitations, environment (which includes atmosphere and food supply) and also evolutionary competition. IMO. First thing is to determine the size limit under current circumstances and then make some experimental or genetic data eligible for application between species. Something like that. At any rate; thanks all for the discussion and please bring your ideas to the table by all means.
     
  15. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    It seems like you are searching for a solution to a problem that doesn't exist.
     
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  16. iceaura Valued Senior Member

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    Sometimes overlooked:
    At least some dinosaurs had birdlike lungs - more efficient than mammalian design.
    Oxygen levels were higher.
    The productive (warm weather, flatter landscape) contiguous land areas available to dinos were larger - larger contiguous available land area correlates with larger body size.
     
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  17. Scott Myers Newbie Registered Senior Member

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    Well, it's at the very least a problem in the minds of some; myself included. Like I said; there has to be some basic limit to size in any environment. What these limits are is my interest and why. It's just a thought experiment and a reason to study something I knew little about.
     
  18. Scott Myers Newbie Registered Senior Member

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    Additionally;

    The problem is certainly a real problem for the sauropods. Even if the landscape was completely reset, and food supplies became difficult, it would have been difficult for any of the classes. Small sauropods should have been able to make it to some count if there were a limit to what could survive after the crater. Given an even playing field, perhaps the mammals were just superior. I would lean toward believing there were additional factors that included major atmospheric changes. After all, we know the climate had some drastic changes. We know the climate was more evenly distributed and less extreme due to location on the globe. The atmosphere being heavier might have contributed to all of these things we sort of know to be true. I am convinced this also contributed to what, or who, survived and propagated after the mass extinction event. Why not? What would lead us to believe this could NOT have also contributed to the outcome we see around us today in the great lottery?
     

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