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The evolution of bipedalism

Discussion in 'Podiatry Trivia' started by scotfoot, Oct 27, 2017.

  1. CEngelbrecht

    CEngelbrecht Active Member

    It has never been an issue.

    https://en.wikipedia.org/wiki/Gathering_seafood_by_hand

    We don't exactly look like gibbons today, do we? Some pressure must have been going on to shape us the way we are.
    [​IMG]
    [​IMG]
    Just add water, it all adds up, like nothing else can. It's not rocket science.

    I'm sorry, did you just say, that the human foot is more flexible than the chimpanzee one? Seriously?
    [​IMG] [​IMG]
    It's getting more and more Magic Bullet Theory in here. Why is it such a problem, if our unique features amongst the apes are related to water? So what, if we're an old beach ape?

    Yes, we descend from brachiating apes as old as 35mya, and as young as ~10mya. That's the gibbon like stage in our evolution you're talking about. That's the mutual origin of all simians. And that is likely a big part of why all simian species become predictably bipedal in shallow water, and thus why it became habitual in human beings. As an exaptation to their forelimbs originally being adapted to dynamic interaction with the surroundings and not constant contact with the ground.
    [​IMG]
    [​IMG]
     
  2. scotfoot

    scotfoot Active Member

    Last edited: Nov 11, 2017
  3. CEngelbrecht

    CEngelbrecht Active Member

    They're rubbish for climbing, that's for sure. What exactly is your point, that our foot is closer to the gibbons' than to the chimp's?

    [​IMG]
    [​IMG]

    For whatever reason and in whatever substrate, human habitual bipedalism on a vertical spine shaped the human foot towards its unique form amongst the apes. And if you don't add water and selection for increased hydrodynamics, you have no selective reason for hominins to evolve that. Climbing doesn't explain it, 'cause then we would see the same principle in e.g. gibbons. Moving about on open grasslands doesn't explain it, 'cause then we would see it in e.g. baboons. There's no convergent evolution to find for these unique traits... unless you add water. Why is this such a problem?

    Other mammal taxa have semiaquatic ancestry. Elephants, rhinos, tapirs, suids, shrews. No problem what so ever for anthropologists. Why all this hysteria because an ape likely went in and out of the water over the eons as well? Is it only because it's ourselves and we always love to delude ourselves into thinking, that we can make up our own rules in the tree of life?

     
  4. scotfoot

    scotfoot Active Member

    Imagine the following hypothetical situation .
    First imagine a small lake about the size of a football pitch and about 10 feet deep in the middle . Now put a boat in the center of the lake and place a man ,with no experience of swimming in water, in said boat . Now add in an adult of each of the following species and all of which have no experience of swimming . Hedgehog ,cat , dog , mouse ,sheep ,pig ,emu, badger,squirrel, goat,horse,hamster,and an aardvark .
    Now let's say the boat sinks and all these animals are tipped into the water alongside our man . What happens ?
    All the animals can swim instinctively and make it to shore. And the man drowns .

    Aquatic ape theory !
     
  5. Rob Kidd

    Rob Kidd Well-Known Member

    In partial reply and comment to the feet above, Christian and others please note the attached plot. This is a canonical variates plot of variates (AKA Axes) one against two of a series of function dimensions that have been indexed to emphasise functionally important features. In doing so it does de-emphasise raw size (that is another ball park, let's not go there to play today!).

    Ignore "8". Now look at the positions of the African apes, H. Sapiens and Pongo. They occupy corners of a triangle that could be interpreted as representing the three known locomotor patterns in extant apes: bipedalism, Knuckle-walking, and some variety of arborealism.

    However: beware the false trichotomy; do not assume that these are the only possible locomotor behaviours.

    8 is the talus of OH8 - Olduvai hominid 8 from the Olduvai gorge. The closer it fits to another species the more similar in form and therefore function it is to that species. OH8 clearly had an arboreal aspect to its lifestyle. While there is no evidence what-so-ever (whatever you have been told) that OH8 is a direct ancestor of ours (ancestor yes, direct, who knows?) this tells us that an ancestor of H. sapiens does have an arboreal aspect to its locomotion.

    Thus, it is not surprising that one is picking up gibbon-like functional affinities. However please note the HUGE difference in overall proportions.

    There no evidence at all for a knuckle walking intermediary between an arboreal and bipedal-type locomotion. The question really is whether the early bipedal locomotion was equatic or terrestrial.............

    Rob
     

    Attached Files:

  6. CEngelbrecht

    CEngelbrecht Active Member

    Uhuh.

    Crash survivors swam for six hours | The Independent
     
  7. scotfoot

    scotfoot Active Member

    Rob ,the foot of an extant gibbon is indeed very different from the Homo Sapien foot which is closer to that of other extant apes such as the chimpanzee .
    It is also true that there is no proof that the last common ancestor (LCA) of Homo and Pan was close to Pan in phenotype although some think this to be the case .
    What strikes me as possible is that the last common ancestor was similar to Pan and this animal gave rise to a gibbon like animal which ,through brachiation , developed a pelvis better adapted to walking bipedally than the original LCA .
    Loss of habitat may have later forced this animal to the ground where ,through atavism , if may quickly have reacquired a more pan like foot but which may have retained some gibbon like qualities .

    Gerry
     
  8. CEngelbrecht

    CEngelbrecht Active Member

    One big problem with that suggested scenario: Homo would then have no selective reason for losing the thumb-like big toe still present on all other apes and instead evolve one, that is parallel to the other toes. Then the conditions would've been exactly the same for both Homo and Pan.

    [​IMG] [​IMG] [​IMG]
    Any particular reason why the human big toe couldn't possibly have been selected for increased hydrodynamics? Then and only then it all adds up.

     
    Last edited: Nov 13, 2017
  9. scotfoot

    scotfoot Active Member

    Christian , in thread 37 you wrote -

    " If the human foot should have evolved completely dry e.g. for bipedal running, it's then peculiar, that the foot didn't keep the outward big toe as in all other apes, since that would otherwise create better "tri-pod" stability for each running step. "

    Does anyone else think the same way about this "tri-pod" as you do ? Anyone at all ?
     
  10. CEngelbrecht

    CEngelbrecht Active Member

    We don't have the outward big toe, as the only hominoid. Latest fossil hominoid to have it is Ardipithecus. Why would losing it be an energy benefit for bipedal running?

    Exactly, it isn't. Conversely, it would be an energy benefit for gliding through water through less drag.
     
    Last edited: Nov 13, 2017
  11. Rob Kidd

    Rob Kidd Well-Known Member

    Gerry, in reply #47 you said:

    Rob ,the foot of an extant gibbon is indeed very different from the Homo Sapien foot which is closer to that of other extant apes such as the chimpanzee .
    It is also true that there is no proof that the last common ancestor (LCA) of Homo and Pan was close to Pan in phenotype although some think this to be the case .
    What strikes me as possible is that the last common ancestor was similar to Pan and this animal gave rise to a gibbon like animal which ,through brachiation , developed a pelvis better adapted to walking bipedally than the original LCA .
    Loss of habitat may have later forced this animal to the ground where ,through atavism , if may quickly have reacquired a more pan like foot but which may have retained some gibbon like qualities .


    Those (pitifully sparce) remains that we have of prehuman fossil foot bones would not agree with this. All the available evidence (which is three parts of bugger all), suggests that the first ray had become non-divergent before leaving the tree. While at the same time, the hindfoot was still of an arboreal type. This is typified by Australopithecus sediba, which to my knowledge, has the one complete calcaneus of the era.

    You use the term "atavism" in an odd manner - an evolutionary throw back. You seem to be suggesting that Homo, upon landing on the ground acquired a chimp-like foot, including its first ray.

    Christian, in your thread #37 post, the comments re: Big toe:

    If the human foot should have evolved completely dry e.g. for bipedal running, it's then peculiar, that the foot didn't keep the outward big toe as in all other apes, since that would otherwise create better "tri-pod" stability for each running step.

    I find this totally at odds with what we know about a) human evolution, and 2) the biomechanics of bipedal gait. While I am no expert in biomechanics, I would suggest that the presence of a divergent first ray would be a disaster for the development of an efficient bipedal locomotion. Start off with the windlass and the support of the arch during (in particular), the propulsive phase of gait.

    Rob



     
  12. scotfoot

    scotfoot Active Member

    I am really just trying to explore ways in which a viable biped could come about . If an species starts out with a certain phenotype and then this alters due to a new phenotype due to environmental factors , then can some of the original characteristics randomly re-emerge and be selected for , if the environment reverts back to the original state .( Over many thousands of years )
     
  13. CEngelbrecht

    CEngelbrecht Active Member

    By doing this for a couple of hundred thousand years.
    [​IMG] [​IMG]

    Even if the above should somehow not illustrate the origin of human bipedalism, you can't say it's not a reasonable thought. Considering that ... every ... single ... ape and monkey species on planet Earth becomes vertically bipedal in shallow water.

    Like the elephant group, you mean? All elephants, living or extinct, descend from semiaquatic creatures ~35mya. While some elephantidea species migrated to arctic regions and reevolved fur, their ancestors had previously lost in the water, as mammoths and mastodonts. Humans are not the only mammal taxa to wade into the water and leave it again, 'cause water bodies come and go across the geological calendar. Often you'd have to adapt to drier conditions or die out, though you keep traits evolved from the eras of being in the water.



    It's not at all controversial or insane to talk about swimming elephants in paleontology. Why is it such rot to talk about swimming apes in paleoanthropology, when you have all the scars of evolution on the body of those apes to show for it?

    [​IMG]

    It's only because it's ourselves, isn't it? We can't study ourselves without breaking out the pitchforks. Here we have answers to a host of questions left over from Darwin and Wallace about how we came to be, and all we do is trying to burn the discoverer.
     
  14. scotfoot

    scotfoot Active Member

    "Christian, in your thread #37 post, the comments re: Big toe:

    If the human foot should have evolved completely dry e.g. for bipedal running, it's then peculiar, that the foot didn't keep the outward big toe as in all other apes, since that would otherwise create better "tri-pod" stability for each running step.

    I find this totally at odds with what we know about a) human evolution, and 2) the biomechanics of bipedal gait. While I am no expert in biomechanics, I would suggest that the presence of a divergent first ray would be a disaster for the development of an efficient bipedal locomotion. Start off with the windlass and the support of the arch during (in particular), the propulsive phase of gait.

    Rob"

    Any chance you could respond directly to this rebuttal of your tri-pod theory ?
     
  15. CEngelbrecht

    CEngelbrecht Active Member

    Why haven't we seen an inkling of this in e.g. grassland baboons? No bipedalism, no inward big-toe.

    [​IMG]

    The savannah hypothesis has been dead for decades, it cannot be supported by the standing evidence. So somehow, our ancestors evolved vertical bipedalism remaining in a woodland scenario, the same scenario chimps and gorillas evolved knuckle-walking in.

    [​IMG]

    If we don't add the bloody water, which is already supported by all (all) simians being bipedal in water (AND loss of fur, AND the big brain, AND the chubby infants, AND the hooded nose, AND exceptional diving ability, AND ...), then we have no selective reason what so ever for Homo to evolve in a completely different direction than Pan and Gorilla. Considering convergent evolution, then we would've been knuckle-walkers too. Which we ain't. There's only water left to explain it.
     
  16. scotfoot

    scotfoot Active Member

    And so ,to conclude my involvement in this thread , the gibbon like hominin I have been speaking about might quickly have achieved larger size (over generations of course ) once freed from the constraints of brachiation in the forest canopy, and gone on to evolve into me ,Christian and other stick wielding homosapiens .Most of whom can't swim at all !

    Cheers

    Gerry
     
  17. CEngelbrecht

    CEngelbrecht Active Member

    Which is why gorillas are the largest extant hominoid, I gather? Only eclipsed by extinct Indian gigantopithecus, ancestor to extant orangutans.

    [​IMG]

    Why is it such a problem with water having affected our unique evolution? Don't you take regular showers?
     
  18. SingaPod

    SingaPod Member

    Isn't it more likely that the development of bipedalism is multi-factorial.

    For example tool use, our simian relatives utilize tools for various purposes, however due to their method of locomotion it is difficult for them to transport tools so they tend to use simple tools that can be whipped up rapidly. Once you are bipedal even to a limited extent you gain the ability to carry things with you. This allows you to modify tools to improve them which in turn allows you to increase your efficiency in whatever task the tool is used for, this in turn makes you better at the task which increases your chances of survival. This results in a cyclical pressure on both bipedalism and tool use/improvement, as tool use aids survival so is selected for but as bipedalism allows for you to have free hands to carry and use those tools that would also be selected for at the same time.

    The aquatic or rather semi-aquatic ape theory (which to my knowledge is generally related to living alongside sea coasts) has the advantage that it fills some of the problems of the older savannah ape theory. One of these problems is that the resources needed to build the large complex brain that hominids developed are rare in a savannah environment while being abundant along the coastline. As seafood often requires more sophisticated methods to gather this may also have been a spur to tool use which as outlined above could have also spurred bipedalism. The advantages of bipedalism are evident in a situation where wading in the water to gather food.

    One other factor to consider is a hunting method used by many hunter-gathering societies, and no doubt used by earlier varieties of hominid as well, which is exhaustion hunting. This is where animals are either kept from water until they collapse from dehydration or where they are caused to run until such a point that they overheat/collapse from exhaustion. Humans are remarkably good at heat management, hairlessness helps with this, if improved locomotion allows our ancestors to take advantage of this fact then it would be a major driving force in improving bipedal locomotion.

    Remember it doesn't have to be the same thing all the way through driving this process. Certain elements of bipedalism may also not at the time been advantageous they may have just not been so deleterious that they would prevent genes being passed on.
     
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