Why do we walk upright?

Discussion in 'Biology & Genetics' started by Oniw17, Feb 21, 2007.

  1. valich Registered Senior Member

    Messages:
    3,501
    Yeah. And you're a slimy "troll" evading the question with nonsense as usual. Go ahead. Start instigating with your usual bullshit "little obnoxious invertedness" and I'll post a realistic photo of your photorealistic "inverted self," and then you can go cry to the administrators. You're an old grump : a useless obnoxious little shit instigator.
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. invert_nexus Ze do caixao Valued Senior Member

    Messages:
    9,686
    Hahaha!
    Man. You're like all sensitive and stuff now, aren't you?
    I didn't even have to ridicule you in the least little bit for you to react as if I had.
    Excellent.

    Anyway.
    The slippery slope you slid down was quite simple really.
    I'll explain seeing as how you are unable to fathom it.

    I mention the benefits of early upright humans being able to see further in their new savannah conditions.
    You then go the whole hog and assume that if it's such a benefit that we should all be giraffes.

    The problems with this are many.
    One, even though there are evolutionary advantages to walking upright in terms of vision across a wide open savannah, there are other factors that prevent such a drastic shift from taking place.
    Sexual selection being one of these factors.
    Time being another (the amount of time between then and now is hardly enough to evolve giraffes out of apes, eh?)
    Various other factors as well, I should imagine. There is likely a sweet spot of height and neck length where both a shorter and greater height are less evolutionary advantageous for whatever reasons.

    So, Mr. Valich, we are not giraffes because we are not under the same selective pressures which led to the formation of the giraffe. Nor are we dealing with the same time scale in which the giraffe neck appeared.

    Elementary stuff, really.
    Maybe you can now write a wikipedia article on it? Why humans aren't giraffes?

    (A fiurther point to note is that giraffe necks are not solely evolved for watch duty. In fact, it might well be said that this was an afterthought. Making it a form of spandrel in fact.)
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. invert_nexus Ze do caixao Valued Senior Member

    Messages:
    9,686
    Why don't you post the picture you just pm'd me you little weasel?
    Go ahead. I dare you.
    Ordinarily, I'd just give a little chuckle and go about my way, but since you're such a slimy little fuck I gave a chuckle and then forwarded it James and Plazma. I could have just given you an infraction outright as I am a moderator and this is well within my authority to do so, but I'll let them decide what to do with you.

    Your reaction is priceless though.
    You're really a fucked up dude. You do know that, don't you?

    I wonder if your broken brain recalls that I first used this line on you? You are really as unoriginal as a brick wall. Nothing inside of you but regurgitated nonsense, yes?

    Ha!
    That's you, you little turd.
    Care to take a vote on it?
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. valich Registered Senior Member

    Messages:
    3,501
    Because it is not appropriate content to post on a public domain, nor is it scientific, as I try to make this forum be. But it is very appropriate for just who and what you are and all the nonsense shit you've always given me. You're always putting people down, as you're doing right now, and as you did in the post before this. Then the entire forum drifts off into condescending ridicule, nonsense and garbage posts that brings the entire reputation of Sciforums down. As I'm sure you will do from here.

    Little Invertedness Nonsense: the Little Man with the Broken Brain. Come to my house and let's have a chat.

    Everytime I post now, you immediately see it and post a condescending reply. That's called "trolling." If the administrator(s) are consistent in their judgement, they will disapprove your "trolling" actions. What's it going to take to stop your condescending harassment in order to bring the reputation and scientific quality of Sciforums up to what it should be? You just don't learn.

    This forum is dead. Let's see what the following posts will be. Obviously downhill by you with nothing constructive to the subject or content.
     
    Last edited: Mar 1, 2007
  8. invert_nexus Ze do caixao Valued Senior Member

    Messages:
    9,686
    That's what's so funny, Valich.
    I didn't even ridicule you this time as you weren't being completely outrageously stupid as usual. Just a bit of a slippery slope. Then you act like I pissed on your mother or something.

    Anyway.
    Let's see here:

    More imitation. I used this one on you.

    That's your every post, Mr. Valich.
    Again. Care to take a vote on it?
    Everyone knows you're a moron. You know that, don't you?
    Who are you trying to kid?

    Why, if I didn't know any better, I'd think that this was a threat of physical violence... That could get you banned, Mr. Valich.
     
  9. invert_nexus Ze do caixao Valued Senior Member

    Messages:
    9,686
    Do you have any sort of proof of this behavior?
    I think not, since I haven't responded to a post of yours in quite some time.
    And, in fact, I first responded to this thread not to ridicule you, or even respond to you, but simply to interject a simple idea which had not yet been mentioned. The benefits of upright posture on vision in an open terrain.

    Then complain to the admin.

    Frankly, getting rid of you would be a good first step to raising the scientific bar of the forums. You're a complete crackpot and are well known for such.

    However, I've never tried to get you banned because Sciforums is open for a wide variety of discussions. Even crackpots such as yourself are welcome.

    Again. You speak of yourself.
     
  10. spuriousmonkey Banned Banned

    Messages:
    24,066
    Back to the topic:
    Why do we walk upright?
     
  11. invert_nexus Ze do caixao Valued Senior Member

    Messages:
    9,686
    Sorry, Spurious.
    You'll note that I didn't get mean until after Valich decided to send me a rather nasty pornographic pm.


    Anyway.
    An often overlooked aspect to the shift from all-fours to an upright posture is in the ligature holding the organs to the spine.
    The organs in a crawling animal hang down from the spine. And, if it tried to walk upright, the organs wouldn't hang properly and the animal would die because of this.
    Our organs hang down from the rib cage. A necessary pre-adaptation to upright posture.

    Of course, this adaptation occurred long before a fully upright stance, but is one of a multitude of adaptations or exaptations that needed to occur before an upright posture could be attained.


    On a somewhat related tangent, genetic evidence seems to suggest that the split between the human and chimpanzee lineages might have occurred as early as four million years ago.
    http://sciencenow.sciencemag.org/cgi/content/full/2007/227/2
     
  12. valich Registered Senior Member

    Messages:
    3,501
    We walk upright for heat dissipation in the hot climates that we evolved in.

    FYI: Giraffes have tall necks that are advantageous for butting competitions over a female, not to see farther or to forage in the treetops as was previously thought. The comment was meant to be a pun on your suggestion.
     
  13. Idle Mind What the hell, man? Valued Senior Member

    Messages:
    1,709
    What?!? Please tell me you're not serious about any of this...
     
  14. valich Registered Senior Member

    Messages:
    3,501
    Giraffes have butting competitions with their necks to fight over the female. The ones with the longer necks win. Research it. Have you ever seen a giraffe forage for food? Normally their necks are lowered so their heads can reach the lower vegetation.

    Research study by Robert Simmons and Lue Scheepers: "Analysis supports that long necks allow giraffes to use their heads as effective weapons for battering their opponents."

    As I said, I read the article about heat dissipation as being an evolutionary advantageous trait in a very detailed National Geographic article many years back. It was very persuasive and I haven't been persuaded by any other better theory since. I'm trying to locate this article because it had excellent heat radiation diagrams of the human body in various positions that offerred extremely compelling evidence. The person who did/does most of the research on this is P.E. Wheeler (1984, 1991):

    http://www.jqjacobs.net/anthro/paleo/bipedalism.html

    http://www.mc.maricopa.edu/dept/d10/asb/anthro2003/origins/bipedality.html

    Bipedalism raises most of the body above the ground, so that the skin contacts cooler and faster-moving air currents. This favors heat dissipation through convection. Allowing for variation in environmental conditions and vegetation, hominids lose about one-third more heat through convection by adopting a bipedal posture. Bipedalism at low speeds also uses less energy than does quadrupedalism or the knuckle walking used by African apes. This reduces both dietary requirement, by reducing the time and effort spent foraging, and the rate at which heat is generated internally as a byproduct of muscular activity.

    This also explains hair loss since hair, or fur, is a thermal insulator and inhibits heat dissipation:

    http://www.modernhumanorigins.net/anth501.html

    As hominids developed an upright posture and bipedalism, additional thermal regulators - circulatory system thermal "radiators" - developed in and around the brain that are absent in quadrapeds. There's a few research articles on this as well that can easily be found.
     
    Last edited: Mar 6, 2007
  15. iceaura Valued Senior Member

    Messages:
    24,041
    The advantages of bipedal walking that depend on the creature already being efficiently bipedal - thermoregulation, tool carrying, etc - cannot explain the evolution of bipedalism in the first place.

    The transitional forms have no such advantages. What has to be explained is the advantage a tree ape with no bipedal modifications would gain by walking on its short back legs for long distances or long times.

    Baboons, and several non-ape animals, came down out of trees unto savannahs onto four feet. They can spy predators, and get away from them at high speed into trees. They can cover long distances over dry ground much more swiftly and efficiently than a chimp on its hind legs, carrying a baby or food even.

    The evolutionary pressures on the humanoid precursors must have been very unusual, somehow.

    One possibility that actually makes sense is isolation on a relatively predator-free island or swamp area that gradually lost its trees. The bipedalism would then have evolved among wading apes, foraging in shallow water or traveling across tide-flooded landscape - the incremental advantages there would be obvious, and not require great efficiency in the transitional forms. A lot of the initial problems of upright stance - the organ displacement, the back strain, etc - would be taken care of by the support of the water.

    Shallow water offers a rich source of food almost ideal for human nutrition, most of which humans can (by amazing coincidence) process without tools and eat raw with enjoyment.

    This would also help account for the unusual throat morphology of humans, allowing very great breath control - more like a seal than a chimp - the extra layer of fat under the skin (not what an animal having cooling problems would want), the odd absence of actual water-efficient sweat glands for cooling (humans sweat with modified oil glands - again, not at all what one would specify for cooling a dry-land endurance runner, but of obvious use for a mammal in and out of water all day), etc etc.

    And of course humans really, really like to hang out at the beach, live overlooking water, etc. The environment suits us, physically and psychologically.

    But hey, it's only a possibility. The key is that the subsequent advantages don't explain the evolution. We didn't evolve to be endurance runners, or tool users.
     
  16. valich Registered Senior Member

    Messages:
    3,501
    There's no suggestion that they were morphologically "efficiently bipedal" before they initially became or tried to become bipedal. The efficiency and morphological fitness to becoming permanently bipedal would have evolved afterwards. Initially, bipedalism was an efficient thermoregulation, and an advantageous transitional form. Apes and chimps lived in the jungles and trees while hominids went into the open savannah. They were no longer able to scamper back up into trees. Thus another reason for the transition.

    This transition also explains hair loss, just like the ecohabitat of the Hairless Dog compared to the thick insulating fur of a Northern Grizzly.

    Sweating became extremely effective in the absence of heavy body hair, and is maladaptive in the presence of heavy fur. Effective sweating requires as little hair cover as possible, as it needs air contact - moving air - over the skin to remove the heated sweat. When hominids became bipedal, more moving air contacted their body. The number of sweat glands increased. There was also a transition to "eccrine" sweating glands with a very high secretory level that are found in humans that evolved simultaneously due to bipedalism and a smooth hairless skin.
     
    Last edited: Mar 10, 2007
  17. Athelwulf Rest in peace Kurt... Registered Senior Member

    Messages:
    5,060
    We most likely walk upright because it was somehow beneficial for us to do so. It offered an advantage over the more primitive forms of locomotion. Our bodies then gradually and incrementally evolved to better suit this new behavior. The end result is that those who did decide to walk had a further advantage over those who decided not to.

    I'm sure people have said this already, but fuck it.

    It's worth noting that I heard once that our spines are still largely built for quadrupedal movement. This is why back problems are common. Whether or not we're still evolving to better handle this novel form of locomotion is debatable. I'd say that due to our new, more civilized lifestyles, unprecedented among the animal kingdom or even among all of life on Earth, the question of whether or not we could survive better with a spine better built for upright, bipedal movement is now moot. Any advantages it could offer could be at best negligible.

    Thread Tools > Edit Thread, or something to that effect.
     
  18. spuriousmonkey Banned Banned

    Messages:
    24,066
    I suggest you read the entire thread before posting something superfluous or check the title instead.
     
  19. iceaura Valued Senior Member

    Messages:
    24,041
    The only problem with that is that bipedalism is not efficiently thermoregulatory until after the animal is efficiently bipedal - before that, it's hard work that overheats the suffering beastie. There are very few advantages to the transitional stages between quad and bipedalism - and consequently, despite the widespread need for such common abilities as thermoregulation, very few animals that have made that transition.
    Yes. So we need an environment in which inefficient and unfit bipedalism, for long times and long distances, by an ape covered with hair, is an advantage. The hot - or cold - savannah is not one of those environments.
    Loss of trees for safety would select powerfully for speed and agility on the ground - four legs, like every other savannah-adapted tree animal. You cannot be seriously suggesting that a transitional hairy ape, almost unable to walk, let alone run, "went out into the savannah" full of leopards on its short back legs.

    That isn't true. Horses, for example, sweat quite effectively - using sweat glands that don't waste oil and salt. Humans have an extra layer of insulating fat, and poorly designed sweat glands that waste oil and salt - these are strange adaptations, for an animal originally and fundamentally interested in cooling itself.

    So the need for cooling probably came later - after the hominids had invaded the savannah, and had the ability to cover long distances on the ground, they could find advantage in doing this under the noonday sun.

    (There are a lot more hairy humans than quadrupedal ones - hair loss is more recent by far than bipedalism, by that evidence. )
     
  20. valich Registered Senior Member

    Messages:
    3,501
    Nice observations and analyses. Suggest the occurence of a transitional habitat. I stand behind the last quote: I've never seen a horse dripping with sweat like a human, then easily and efficiently wiping the excess off. Humans evolved quite efficient "eccrine" sweating glands and evolved a much higher concentration of them. Perhaps we can compare a density concentration of sweating gland and eccrine glands. I suppose contemplating which came first, hair loss or bipedalism, is a chick-egg question. No fossil evidence available. But we can infer from existing species - example, Mexican Hairless Dog, etc., Double-Layered Fur in Northern Breeds, etc. - that hair loss was caused by heat, or hotter near-equatorial regions.

    Also, long legs evolved later for a running advantage, although I'm not saying that humans run faster, but primitive hominids were very short, aka. Lucy.
     
  21. MetaKron Registered Senior Member

    Messages:
    5,502
    It is not even physically possible to maintain health and life if you sweat without shedding salt and oil. The balance between water and salt has to be maintained.

    Horses can sweat so much salt that they can develop a visible crust.
     
  22. spuriousmonkey Banned Banned

    Messages:
    24,066
    The human sweat glands are brilliantly designed for keeping cool. That's why bushmen in Africa can hunt down prey by running after them till the prey succumbs to heat exhaustion. The human however manages to stay just a notch away from heat exhaustion because of his 'sweat' physiology.
     
  23. iceaura Valued Senior Member

    Messages:
    24,041
    That is an effect of inefficiency, not efficiency - the excess does not help cool. The most cooling would be from a very, very thin but quickly and exactly replaced film of almost pure water.

    Depends on design. Humans have to sweat salt and oil because they have some built in inefficiencies in their cooling system. So they have to seek out salt, in their diet, unless it is plentiful in their environment.

    Humans need a lot more salt in their diet than a normal savannah animal - a poor adaptation for that environment. It wouldn't matter, of course, near the ocean.

    AFAIK horses only lose salt when worked very hard, so that subsidiary glands kick in - their ordinary sweat glands don't leak that much salt. And even then, they don't lose as much proportionately by weight as a human does just walking around in the sun.
    In a sense, yes - but they do it the way a dragster gets horsepower: efficiency is secondary. They waste a lot of water, salt, and oil. Again, this only matters if water and salt are in short supply, such as on a savannah - on an ocean beach, no problem. And the oil would be a postive asset.
     

Share This Page