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  1. Petter is offline

    12th level logic wielder

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    Posted On:
    5/25/2011 6:33pm


     Style: BJJ, judo, rapier

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    Hell yeah! Hell no!
    Quote Originally Posted by DCS View Post
    “The results of this study are consistent with the hypothesis that our ancestors adopted bipedal posture so that males would be better at beating and killing each other when competing for females,”

    And females went bipedal for?
    …The same reason males have nipples: A trait selected for in one sex may be carried across to the other, unless there’s positive selection to create sexual dimorphism (or a gene vital for the trait just happens to be carried on a sex chromosome). I think the article is rather silly, but this isn’t one of the good reasons against it.

    Human evolution is a sexy topic that attracts boatloads more speculation than there’s evidence to support, and it’s always easy to come up with Just So Stories. It’s not quite as bad a field for it as evolutionary psychology, but it’s pretty close. Aquatic Apes, anyone?
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  2. DCS is offline
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    Posted On:
    5/25/2011 6:49pm

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    Quote Originally Posted by Petter View Post
    …The same reason males have nipples: A trait selected for in one sex may be carried across to the other, unless there’s positive selection to create sexual dimorphism (or a gene vital for the trait just happens to be carried on a sex chromosome). I think the article is rather silly, but this isn’t one of the good reasons against it.
    Lots of male mammals (not sure about some australian things) have nipples, but male deers have big horns while females haven't.

    Females should not have to went bipedal if bipedalism had its origins in the kind of mating behaviour the article assumes was the norm. Bipedal posture complicated things a lot for females. They should have stayed in 20 nails while the males facepunched each other.
    Last edited by DCS; 5/25/2011 6:53pm at .
  3. TaeBo_Master is offline
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    Posted On:
    5/25/2011 9:51pm

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     Style: Judo, Jujitsu

    --
    Hell yeah! Hell no!
    The better-cooling hypothesis is one that I've heard from a number of sources that makes a lot of sense. Another is to gain a better sight line. As we came out of the trees onto savannah covered in moderately high grass, standing upright gave the advantage of spotting predators from a greater distance. Being above the grass gives you a better view than being in it. I've also heard it speculated that it was for energy efficiency in travel. As the species began to acquire a greater range and migrated further, it cost less energy to do so walking on 2 legs than 4.

    The last hypothesis would obviously have occurred slowly over the course of many species of ancient hominids. Perhaps it's why as the proto-species progress, they gradually become more bipedal and have larger ranges. This doesn't explain, however, the prevalence of quadrupeds with large ranges.

    The real question is why bipedalism is still so limited in the animal world. Bipedalism has evolved several times in history, beginning as far back as the predecessors to the dinosaurs. It's been around a long time, and you'd think if it was evolutionarily so advantageous, you'd see it very commonly. But you only see it in a small handful of animals, such as macropods (the group including kangaroos) and primates. I'm excluding birds, because their unique evolutionary track has given them quasi-bipedalism (quasi because walking on the legs is not really their main mode of transport) because they have to have wings. Among these bipedal groups, humans are virtually the only ones that are exclusively bipedal in the fashion we consider normal (i.e. walking, running). Macropods use their two legs simultaneously to hop, and are virtually incapable of walking or running. Most primates that are bipedal alternate between bipedalism and quadrupedalism, or are tree-dwellers. Humans can crawl on hands and knees, but this is typically a specialty posture (meaning it's used to perform a specific task), and is generally not used for actual transportation. 'Tis a bizarre question.
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  4. P Marsh is offline

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    Posted On:
    5/26/2011 1:39am


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    Bipedalism might just be a unique trait of the great apes similar to serpents having no legs at all, it simply became what worked better for our species. Complex hunting weapons like bows and spears most likely did not factor into the decision due to their appearance of about 2.5 million years ago (the Achelian hand-axe, sic. my archeology notes) 1.5 million years after the transition to an upright stance.

    Seeing above the grass is also one explanation that doesn't really fit well with me. Looking above tall grass for something that might be under the grass line doesn't do much considering that the reason both our eyes are front facing is so we can see past object that are close to our faces such as foliage and not for depth perception as most people would remark. Most land carnivores have evolved this trait while herbivores did not.

    If I were to hazard a guess based on nothing I'd think it would have occurred when humanity started hunting herbivores on the savanna supporting the efficiency argument. Early humans hunted by chasing animals slowly but continuously to exhaust them and then kill them for food.
  5. Petter is offline

    12th level logic wielder

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    Posted On:
    5/26/2011 1:56am


     Style: BJJ, judo, rapier

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    Quote Originally Posted by P Marsh View Post
    Complex hunting weapons like bows and spears most likely did not factor into the decision due to their appearance of about 2.5 million years ago (the Achelian hand-axe, sic. my archeology notes) 1.5 million years after the transition to an upright stance.
    The Achelian hand-axe is, I presume, a prepared tool—a hand-axe that has been deliberately chipped and shaped? When talking about tool use, it may be well to mention and consider tools that either were not specially fashioned (like a plain unshaped rock for bashing) or do not fossilise, like wood spears. It’s also interesting to note that chimpanzees use both of these (anvil stones to chop up food, and sharp sticks to stab bushbabies hiding in hollow trees).
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  6. P Marsh is offline

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    Posted On:
    5/26/2011 2:35am


     Style: Boxing

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    Quote Originally Posted by Petter View Post
    The Achelian hand-axe is, I presume, a prepared tool—a hand-axe that has been deliberately chipped and shaped? When talking about tool use, it may be well to mention and consider tools that either were not specially fashioned (like a plain unshaped rock for bashing) or do not fossilise, like wood spears. It’s also interesting to note that chimpanzees use both of these (anvil stones to chop up food, and sharp sticks to stab bushbabies hiding in hollow trees).
    Its a single sculpted stone in the shape of a tear drop. Might have misread my notes as the Achealian hand-axe was the first discovered but the first tools did appear at 2.5 million years ago.

    Yep misread and jumped the gun.

    First tools were used similar to chimp as means to prepare or access food such as pounding stones to break open bones for the marrow. The Achealian hand-axe didn't come later but it was used as sort of a multipurpose tool for cutting and crushing, maybe even killing animals when caught, I don't know I wasn't around then.

    My point is that they weren't complex and they didn't require an upright position to utilize to their utmost effectiveness. Actual weapons didn't exist unless rocks used to throw at lions or what have you from the safety of a tree count as a weapon (don't really think they do). Bladed items didn't arrive until the upper paleolithic period which was about 40,000 years ago.
  7. Snake Plissken is offline
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    Posted On:
    5/26/2011 7:50am

    supporting member
     

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    Quote Originally Posted by DCS View Post
    And females went bipedal for?
    to get away from the bipedal males
  8. cufaol is offline

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    Posted On:
    5/26/2011 8:11am


     Style: Boxing/Judo/BJJ

    --
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    Quote Originally Posted by TaeBo_Master View Post
    The better-cooling hypothesis is one that I've heard from a number of sources that makes a lot of sense. Another is to gain a better sight line. As we came out of the trees onto savannah covered in moderately high grass, standing upright gave the advantage of spotting predators from a greater distance. Being above the grass gives you a better view than being in it. I've also heard it speculated that it was for energy efficiency in travel. As the species began to acquire a greater range and migrated further, it cost less energy to do so walking on 2 legs than 4.

    The last hypothesis would obviously have occurred slowly over the course of many species of ancient hominids. Perhaps it's why as the proto-species progress, they gradually become more bipedal and have larger ranges. This doesn't explain, however, the prevalence of quadrupeds with large ranges.

    The real question is why bipedalism is still so limited in the animal world. Bipedalism has evolved several times in history, beginning as far back as the predecessors to the dinosaurs. It's been around a long time, and you'd think if it was evolutionarily so advantageous, you'd see it very commonly. But you only see it in a small handful of animals, such as macropods (the group including kangaroos) and primates. I'm excluding birds, because their unique evolutionary track has given them quasi-bipedalism (quasi because walking on the legs is not really their main mode of transport) because they have to have wings. Among these bipedal groups, humans are virtually the only ones that are exclusively bipedal in the fashion we consider normal (i.e. walking, running). Macropods use their two legs simultaneously to hop, and are virtually incapable of walking or running. Most primates that are bipedal alternate between bipedalism and quadrupedalism, or are tree-dwellers. Humans can crawl on hands and knees, but this is typically a specialty posture (meaning it's used to perform a specific task), and is generally not used for actual transportation. 'Tis a bizarre question.
    Isn't it likely that the solution lies in a number of reasons combined rather than just one reason? I mean, the cooling-hypothesis sounds good and the better line of sight may have been a contributing or encouraging bonus. Either way, i am glad we learned to walk on two legs so that now I have my hands free to hit things. :)
  9. Matt Phillips is offline
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    Posted On:
    5/26/2011 9:43am

    supporting member
     Style: Novice Sub Grappler

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    In order for this theory to work, the extra power would have to be used to kill. Either that or females were making their mate selection based on who was the better... oh, wait.
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  10. tao.jonez is offline
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    Posted On:
    5/26/2011 9:51am


     Style: JKD, Jiu Jitsu

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    Hell yeah! Hell no!
    I think it's so we could carry stuff. The "stuff acquisition" gene is a powerful motivator.

    Hoarders and fat people are winning at evolution.
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