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Thread: What prompted primitive man to become bipedal?

  1. #1 What prompted primitive man to become bipedal? 
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    What prompted primitive man to become bipedal? I mean, what were the environmental pressures that made it necessary to stop swinging from trees and start walking upright? Note I'm not asking what advantage it gave us (freeing our hands to use tools), I'm asking what prompted it.


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    But using tools could well have come first, and thus prompted it.


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    That's a good question. To which there are many viable answers, none of which have been completely supported at this point.

    http://en.wikipedia.org/wiki/Biped

    Go to the Evolution - Human section for a review of the various, most prevalent theories.
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    Quote Originally Posted by free radical
    But using tools could well have come first, and thus prompted it.
    that is contradicted by the fossil record : oldest recognisable tools 2.5MYA, oldest signs of bipedalism at least 4MYA

    i'd say hominids became bipedal (at least to some degree) prior to leaving the forests, otherwise they would have been forced to retreat with the forests like the chimps had to do
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    I think they became bipedal so they could wear pants.

    (except for the women of course. They preferred skirts. But then again, the original question was on primitive man).
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    you know spurious, that's a really pants idea 8)
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    I know, I know.

    Apparently the pants were invented to facilitate horse riding. Although not all horse-riding people managed to think of the obvious idea of pants.
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    Africa, the area where our ancestors lived, was once very fertile and completely full of vegetation. Then desertification took control. The vegetation started dieing and the trees where scarce. Our ancestors needed to live in caves and such instead of living amongst the trees.
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    so they lost their eyesight and pigmentation? :?
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    WYSIWYG Moderator marnixR's Avatar
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    although bones HAVE been found in caves, there's preciously little evidence that australopithecines actually LIVED in caves
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    When did fire pits appear in caves?
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    Quote Originally Posted by marnixR
    although bones HAVE been found in caves, there's preciously little evidence that australopithecines actually LIVED in caves
    Caves, dens, whatever they use to live in it wasn't in trees due to desertification. They had to find elsewhere to spend the majority of their time. It is well known that during this time desertification took place in that region.

    As to them losing their eyesight and pigmentation. Where do you get that they lost their eyesight? And they most likely lost their pigmentation when they moved out of Africa northward. Due to the more intense radiation and the non ability to take in the right amounts of vitamin D from the sun with dark skin is when they lost thier pigmentation.
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    Quote Originally Posted by marnixR
    Quote Originally Posted by free radical
    But using tools could well have come first, and thus prompted it.
    that is contradicted by the fossil record : oldest recognisable tools 2.5MYA, oldest signs of bipedalism at least 4MYA
    You mean crafted tools. But any nice stick or stone picked up can be a tool.


    We carry objects to bring them from one place to another. So, I think our spacial memory must be tied to this. One must connect a problem in one location with the objects in another. "Now where did I leave that hammer..."
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    Other apes use tools and are not fully bipedal. It is curious to consider how one influences the other.
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    Quote Originally Posted by paralith
    That's a good question. To which there are many viable answers, none of which have been completely supported at this point.

    http://en.wikipedia.org/wiki/Biped

    Go to the Evolution - Human section for a review of the various, most prevalent theories.
    Ok I change my mind as to how it occured. As given by your link I agree with teh following:

    "And it has even been suggested (e.g. Tanner 1981:165) that male phallic display could have been the initial incentive."
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    Sigh...

    These things occur just as it occurs for other things. Very rarely, if ever, is it a conscious decision by the species.

    The survival of upward walking primates ensured that their descendants would also be upward walking. The amount of offspring by the upward walking primates with less hair seemed to be better than the hairier ones, but I doubt the reason they started walking upright was purely to show off their phallus.
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    Quote Originally Posted by SuperNatendo
    Sigh...

    These things occur just as it occurs for other things. Very rarely, if ever, is it a conscious decision by the species.

    The survival of upward walking primates ensured that their descendants would also be upward walking. The amount of offspring by the upward walking primates with less hair seemed to be better than the hairier ones, but I doubt the reason they started walking upright was purely to show off their phallus.
    Maybe you misunderstand. Phallic display could be a means of competing for mates, and that most certainly has a significant effect on reproductive success. It wouldn't be the weirdest thing accomplished in the name of sexual selection, that's for sure.

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    I'm just saying, considering the fact that most human females claim the visual stimulation just doesn't exist when they see an erect penis, primates walking on two legs for the sole purpose of showing off the phallus would probably attract more homosexual monkeys than those of the opposite sex. The only thing I can see is that it might be possible they compared penis size as a sort of competition (since that still happens today!), But I doubt it had anything to do with females choosing a mate based on the appearance of the phallus considering how most females react to them visually.

    It is quite possible however, that this WAS used as a way to attract a mate, and social and cultural influences have influenced the way modern females say they base their sexual choices when it comes to finding a mate in modern times.

    Yet again, what would prompt females to start walking upright? Just because the "Guys" are doing it?

    I still somehow tend to think that it was more of a convenience thing from switching from trees to the ground. Either way I think it would be good to see what primates do, including the reasons why some walk for miles upright such as the bonobo.
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    Maybe penis size (display) was more influential before monogamy, and clothing.
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    Quote Originally Posted by SuperNatendo
    I'm just saying, considering the fact that most human females claim the visual stimulation just doesn't exist when they see an erect penis, primates walking on two legs for the sole purpose of showing off the phallus would probably attract more homosexual monkeys than those of the opposite sex. The only thing I can see is that it might be possible they compared penis size as a sort of competition (since that still happens today!), But I doubt it had anything to do with females choosing a mate based on the appearance of the phallus considering how most females react to them visually.

    It is quite possible however, that this WAS used as a way to attract a mate, and social and cultural influences have influenced the way modern females say they base their sexual choices when it comes to finding a mate in modern times.
    Well, you provided most of the answer I was going to give. The theory of phallic display only says that it was an initial impetus towards bipedalism, which was then favored for its other advantages.

    Yet again, what would prompt females to start walking upright? Just because the "Guys" are doing it?
    We are assuming that bipedalism is genetic, and a complex behavioral trait such as that is probably not going to be sex-specific. Gorillas are a good example of such intersexual conflict - it is advantageous for males to have large body sizes, but it is not advantageous for females to be so big. However, genes determining body size are not all limited to males, so there is a conflict of fitness for the same genes between males and females of the same species. Assuming this model is correct, something similar probably occurred with bipedalism.

    I'm not saying I think this model is the most likely - it probably isn't. But it has validity enough that it's not completely ridiculous to propose it.
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    unfortunately most of the theories attempting to explain hominid bipedalism fall in the category of just-so-stories : many are plausible one way or another, but for most of them it's darned hard to find conclusive evidence
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    reminds me of a talk I attended not too long ago on the nature of the very first primates.

    It was suggested that they had a distinct set of characteristics that moved towards the more modern ones by a uniform selective pressure.

    But during the talk I kept thinking that the selective pressure could have switched directions many times during the lineage and that then the data would look totally different.

    Similarly, the introduction of bipedalism could have had many causes and could have been the result of what seems conflicting evolutionary pressures.

    In other words, everybody could well be correct, or wrong. Or something in the middle.

    And I doubt we will ever know exactly, although we might be able to get a better idea eventually with a larger and more detailed dataset.

    Or not.

    Anyway,

    did bipedalism make primitive man non-primitive.
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    Quote Originally Posted by spuriousmonkey
    did bipedalism make primitive man non-primitive.
    Non-primitive, I dunno. Rather, WTF haxor, I think. Bipedalism hacks the game engine.

    I think it made us totally intimidate and dominate other species including predators. We know that many animals get up on hind legs to threaten or fight. So, our normal posture is manifestly threatening... heh, not bad. We know that chimps (in groups, always in groups) don't hesitate to chase off predators like big cats. They typically grab sticks and rush the animal, swinging, throwing, waving their arms. It's very effective. So we got even better. Why not wield a walking stick all the time?

    And there's more. Because our bipedal stride - though not so good for speed - is most efficient in the long haul. So we can hunt by simply wearing our prey down. This works real good when every time the prey sees you coming it startles and wastes a lot of energy leaping and skittering to dash a mere 100 meters and think itself safe... for a minute. I see the promise of that predatory WTF hax in how chimps will pursue an animal well out of range, to make sure it's really dealt with. If those chimps were bipedal, they could pursue it 'till it died of exhaustion. Then eat.

    Tripedalism? I wonder if we'll find fossils with walking sticks clearly worn by use? Or maybe signs of asymmetric load in the joints. I wonder if handedness has anything to do with it - since other primates show only slight hand preference in throwing, eating, etc - ?
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    Quote Originally Posted by SuperNatendo
    I'm just saying, considering the fact that most human females claim the visual stimulation just doesn't exist when they see an erect penis...
    I don't know if I believe that. I remember learning about a study that showed females and males react physiologically to sexual stimuli equally. I think for women it depends a lot more on the situation and context, and they're certainly stimulated by a lot more than just physical things. Other than that, I think they lie.
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    Quote Originally Posted by Pong
    I think it made us totally intimidate and dominate other species including predators. We know that many animals get up on hind legs to threaten or fight.
    also, i think it's a lot easier to kick someone in the balls when they stand on their hind legs - but i suppose it's also easier to do the kicking (or throw the kitchen sink at the would-be predator)
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    I find it very hard to believe that bipedalism is a result of male members of the species attempting to show of their groinal regions. Evolution towards bipedalism would take quite a lot longer as to the alternative (which I will describe shortly) if this were the case.

    With my previous argument, despite what you all thought you read, I did not mean humans spent all their time in caves. What I meant was they lived in caves, they had their belongings and their homes in caves. However when they went hunting or foraging for food they came out of their 'houses'. I have since been made aware of another recent finding.

    Though I can't remember where I read this information current thought is that, due to desertification of Africa at this time, long patches of areas were deforested. Australopithecenes lived at the edge of this deforested area. When they went out foraging for food they needed to come out of the jungle. From there they filled their arms up with food and took it back into the jungle for protection. Bipedalism lead to them being able to hold more food in their arms and less of a chance of them getting killed by predators.
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    Quote Originally Posted by BumFluff
    ... What I meant was they lived in caves, they had their belongings and their homes in caves. ...
    i think living in caves came only at a later stage, with the only clear signs of habitation in caves coming from H.sapiens
    Australopithecus bones found in caves are thought to have been washed in, or as the result of leopard kills kept in trees near cave openings
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    Quote Originally Posted by marnixR
    Quote Originally Posted by BumFluff
    ... What I meant was they lived in caves, they had their belongings and their homes in caves. ...
    i think living in caves came only at a later stage, with the only clear signs of habitation in caves coming from H.sapiens
    Australopithecus bones found in caves are thought to have been washed in, or as the result of leopard kills kept in trees near cave openings
    Them living in caves was merely an example of where else they could have moved to once desertification started taking hold of the area. When did monkey start going a different path than man? My guess would be when one became bipedal which would then lead into the loss of body hair (due to cooling, a commonly held belief), to greater tool use and subsequently bigger brains. Giving the theory you gave before on possible evolutionary reason why one group would become bipedal while the other didn't one would reason that one was more sexually impressive than the other one which would give rise to them becoming bipedal for them 'showing off'? If not, what are the reasons why one group became bipedal and the other didn't?

    My reasoning would be the recent findings that Africa went through desertficiation at this time (in fact it still is) is that pockets of the area lost vegetation while pockets didn't. Bipedalism grew from the groups that were within one of these vast stretches of desert mixed with vegetation where human ancestors needed to scavenge and hunt for food on the open plains. This would lead to hunting, travelling and scavenging in packs for increased protection and, given time, the advancement of weapons from stick s and clubs to spears.
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    i seem to remember that there's a theory from some french paleo-anthropologist that goes a bit along those lines
    it's supposed to be caused by the rise of the ethiopian dome around 6 million years, thereby creating a rain shadow and dividing what was coast-to-coast rain forest into rain forest to the west and savannah to the east

    haven't been able to track the article though - i think there was one on the subject in Scientific American several years ago
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    I don't suppose you recall the name of the paleo-athropologist? I'd be interested in reading it.
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    Anybody gonna pick up my walking-stick hypothesis?

    It can be tested in so many ways.

    Gee, ever seen apes use leafy branches for umbrellas? That too: sunshade on the savannah.

    Meanwhile... My Walking Stick - Irving Berlin
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    Quote Originally Posted by BumFluff
    I don't suppose you recall the name of the paleo-athropologist? I'd be interested in reading it.
    i think it's called "East Side Story" and it's by Yves Coppens
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    Hmm i partially agree with the desertification, and sexual selection.

    I think its because of reaching things. Bears stand up to reach honey, or fruits, and so do apes. After this we see our legs growing, so we can reach higher. With these deformed legs, we can't walk anymore on 4 feet. Ah well, we can, but thats increddibly hard to crawl as fast as walking or running. It also costs les energy to stand up and walk, then to walk on 4 feet. If we lead a nomadic life in any way, we should have an advantage. Also, where there are less trees, we get more sun, and when your standing up right, you capture less sunlight on the hottest part of the day. This is a HUGE advantage while hunting. This makes it possible for a man, to outrun a gazelle, just because the gazelle is dehydrated, and the well dranken man is not.

    Probably the use of tools is not the reason for us to evolve, but to thrive.

    Where the sexual selection comes in. Some apes, stand upright to fight for a mate. And the one who is the best equipped gets the girl. So being able to stand better then the other is an advantage.

    Still, Because of the travelling of humans, they collected a huge number of invalid animal virusses, that have ajusted our entire gene structure. This might be the reason why we lost our hair. Our tail, and our feet changed. Because these are parst of other animals, like a catlike creature (feet), a bear (tail), but i have no idea where the bald thing comes from.

    I have no proof for all above.. so don't recite this anywhere if you want anything else then filosophy
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    When you live in caves it is better not to walk upright. You will bang your head on the ceiling quite often.
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  36. #35  
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    Quote Originally Posted by spuriousmonkey
    When you live in caves it is better not to walk upright. You will bang your head on the ceiling quite often.
    the clever caveman finds himself a cave with a high ceiling
    it's only the dunces that have to stoop

    and hey presto, another rough and ready just-so-story explanation for man's intelligence !
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  37. #36  
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    It's brilliant in its simplicity.
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  38. #37 Re: What prompted primitive man to become bipedal? 
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    Quote Originally Posted by gib65
    What prompted primitive man to become bipedal? I mean, what were the environmental pressures that made it necessary to stop swinging from trees and start walking upright? Note I'm not asking what advantage it gave us (freeing our hands to use tools), I'm asking what prompted it.
    Early man was prompted by the invention of the bar counter to stand more upright. Once in bipedal posture ordering a bourbon became much easier as the primative man was more visible to the monkey bartenders.
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