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Thread: Might Chimps and Gorillas be the descendants of a biped ape?

  1. #1 Might Chimps and Gorillas be the descendants of a biped ape? 
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    The reason I ask is because there seems to a large number of bipedal apes in the fossil record.


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  3. #2 Re: Might Chimps and Gorillas be the descendants of a biped  
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    Quote Originally Posted by delsydebothom
    The reason I ask is because there seems to a large number of bipedal apes in the fossil record.
    There is an even larger number of non-bipedal apes in the fossil record.


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  4. #3 Re: Might Chimps and Gorillas be the descendants of a biped 
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    Quote Originally Posted by KALSTER
    Quote Originally Posted by delsydebothom
    The reason I ask is because there seems to a large number of bipedal apes in the fossil record.
    There is an even larger number of non-bipedal apes in the fossil record.
    Ah...then I'd say that the bipeds are disproportionately represented in the media. You'd think the lines leading up to Gorillas, Chips, Orangutans, etc., would be interesting enough to warrant more popular attention.
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    No, no, and …no….Gorillas and chimpanzees are likely to be the closet relatives of humans in the animal kingdom—a recent controversial hypothesis puts the Sumatran Orang-utan as a closer relative to humans than the chimpanzee, but i wouldnt take it seriously.

    However, on the main issue, the Gorilla genus is part of the Homininae subfamily, itself part of the Hominidae family, which is itself as we know, part of the primate order. The Hominidae family is better known as the great apes, a family which embodies humans, chimpanzees, gorillas, orang-utans, and number of extinct primates.

    In response to the question: of all the species composing the Hominidae family, only humans developed bipedal locomotion. Additionally, no species within the homininae subfamily procured bipedal movement other than the more recent ancestor of humans. In short, gorillas are not descended by species possessing bipedal locomotion.

    Here is the rough tree layout: the Hominidae family gave rise to the homininae subfamily, which gave rise to two tribes: the Gorillini and the Hominini. The former gave rise to the genus gorilla, and the latter produced the genus Pan and Homo—of which chimpanzees and humans are derived respectively
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    I'm going to say likely to delsydebothom's question, but only for the homo/pan common ancestor. The femur suggests it was bipedal. This would fit a scenario where our successful ancestor challenged both deeper into jungle and farther into plains, thereby regionally speciating into chimps and humans, and further adapting to our respective environments.

    It's kinda hard to think losing bipedalism adaptive, but that's apparently the course chimps took. I'm unsure how to feel about our role in that, which is ongoing BTW for bonobos driven deeper into the jungle.
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    WYSIWYG Moderator marnixR's Avatar
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    why yes for the chimp but no for the gorilla ?
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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    Quote Originally Posted by Pong
    I'm going to say likely to delsydebothom's question, but only for the homo/pan common ancestor. The femur suggests it was bipedal.
    What homo/pan common ancestor might this be?

    It possible that the chimp/gorilla taxa had an ancestor that was either bipedal or at least more bipedal than now, but its unlikely. All evidence thus far points to a Last Common Ancestor (LCA) at a point of divergence that wasn't bipedal, with bipedal hominids evolving after the split (or perhaps because of the split) in taxa. The Ardipithecus find is an example of this, it's a species that is bipedal or semi-bipedal but genetically the clock for its emergence is after the LCA, but very close to that point.
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    there's really only 2 possible scenarios for the african apes : the ancestral mode of locomotion was knuckle walking and the branch leading to humans developed a bipedal locomotion, or the ancestral way was bipedal and the chimp and the gorilla underwent similar selection pressures to end up with knuckle walking

    the sample size of 3 is too small to compare the probabilities of each scenario, so that means we'll have to try and rely on the fossil record to elucidate the matter - future finds if the current ones are inconclusive
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    Quote Originally Posted by marnixR
    why yes for the chimp but no for the gorilla ?
    I'm sorry I can't answer that. Going by what seems the consensus. The (LCA?) fossils suggestive of bipedalism are about 6MY.

    We do know that chimps have evolved quite a bit in their own right. Comparing human and chimpanzee DNA, the chimps have more adaptive changes than humans, with neutral background changes as a baseline. When you put this in context of our different habitats, it is logical to think part of this adaptation was becoming more quadrupedal for the jungle terrain.

    So basically what I'm suggesting is a common ancestor bipedally comparable to the bonobo, spread and eventually divided by different habitats. I think that culture may have helped define the two populations and kept them from mating. Support that by showing for example that highlands humans more likely raided than intermarried with delta humans, and likewise highlands chimps vs. valley chimps. Presumably our common ancestor adapted incompatible localized cultures also.

    This is awfully speculative though. I'll go with more fossils any day.

    Perhaps the conditions of our common ancestor were in some way adverse to leaving fossils? That itself would be indirectly suggestive of how we evolved.
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    Pong, I'm having a hard time following most of your post, so I'm not entirely sure what you're saying. The LCA for humans and chimps was between 8 and 10 million years ago, which puts it 2 - 4 million years before Ardipithecus.

    Perhaps the conditions of our common ancestor were in some way adverse to leaving fossils? That itself would be indirectly suggestive of how we evolved.
    I would say this is very likely. The environment for the human / chimp LCA was very likely a forest one, which is, by far, the least conducive to creating a fossil record.
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    Quote Originally Posted by SkinWalker
    Pong, I'm having a hard time following most of your post, so I'm not entirely sure what you're saying. The LCA for humans and chimps was between 8 and 10 million years ago, which puts it 2 - 4 million years before Ardipithecus.
    That's the date determined through DNA? I'm not arguing... it's just that far as I know the fossils thought to represent LCA date 6 million.

    Quote Originally Posted by SkinWalker
    Perhaps the conditions of our common ancestor were in some way adverse to leaving fossils? That itself would be indirectly suggestive of how we evolved.
    I would say this is very likely. The environment for the human / chimp LCA was very likely a forest one, which is, by far, the least conducive to creating a fossil record.
    At least I got something right.



    So what do you think of the speciation scenario where some occupy jungle while others more open territory, and both rapidly adapt incompatible cultures which further isolate the populations? Speciation by mutual antagonism... kinda the original racism? By culture here I mean local foraging and survival know-how, early technologies, etc.
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    Isn't it unlikely? Since if chimpanzees and gorillas were descended from a biped ape they would have to gain that trait first, then lose it. Both processes requiring restructuring of the spine (curves to prevent shock) and the skull (movement of the neck entrance).
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    Chimpanzees are further evolved from the LCA than modern humans. In that light it is more telling to say chimps evolved from humans than humans evolved from chimps... although neither is strictly true.
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    WYSIWYG Moderator marnixR's Avatar
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    what's wrong with saying "shared a common ancestor" ?
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    Quote Originally Posted by Golkarian
    Isn't it unlikely? Since if chimpanzees and gorillas were descended from a biped ape they would have to gain that trait first, then lose it. Both processes requiring restructuring of the spine (curves to prevent shock) and the skull (movement of the neck entrance).

    Chimps and gorillas do not appear to be descended from a bipedal ape. All evidence points to the contrary.

    Moreover, chimp and gorilla anatomy is consistent with that of characters derived from earlier, non-bipedal ancestors. The chimp pelvis, for instance, is angled such that bipedalism is awkward (chimps do walk bipedally, just not naturally or easily). The angle of the illiac blade is what provides different muscle placement and center of gravity along with different rotation and flexion where the femur articulates with the pelvis.

    This sort of drastic evolution would be obvious in the fossil record. It isn't. It isn't present at all except in hominid lines going back through Ardipithecus (and so limited in this genus as to be debatable whether or not the hominid was truly bipedal).
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    Quote Originally Posted by SkinWalker
    This sort of drastic evolution
    I suggested "a common ancestor bipedally comparable to the bonobo".

    Anyway by their DNA common chimpanzees evolved more ...drastically... than humans, from last common. So what does that suggest? We are more like the last common than chimps are. That doesn't necessarily apply to skeleton. :?

    I dunno, sometimes I get the feeling people think the other modern great apes represent our ancestors.
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    i suspect you should find traces of a knuckle-walking past in fossils such as Ardipithecus or the early Australopithecus - i haven't followed this debate recently, but did people at some stage not think that such traces could be discerned ?
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    Quote Originally Posted by marnixR
    i suspect you should find traces of a knuckle-walking past in fossils such as Ardipithecus or the early Australopithecus - i haven't followed this debate recently, but did people at some stage not think that such traces could be discerned ?
    I would be surprised if this were true for Australopithecus. As far as I am aware all specimens show a foum magnum that indicates bipedal walking, which in turn would preclude significant knuckle walking.
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    my impression was that there was something in the build of the hand bones that was indicative of a history of knuckle walking, but i could be wrong

    + when i say Australopitchecus, i don't mean the later ones but species like A. anamensis and A. afarensis
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    Quote Originally Posted by SkinWalker
    Quote Originally Posted by Golkarian
    Isn't it unlikely? Since if chimpanzees and gorillas were descended from a biped ape they would have to gain that trait first, then lose it. Both processes requiring restructuring of the spine (curves to prevent shock) and the skull (movement of the neck entrance).

    Chimps and gorillas do not appear to be descended from a bipedal ape. All evidence points to the contrary.

    Moreover, chimp and gorilla anatomy is consistent with that of characters derived from earlier, non-bipedal ancestors. The chimp pelvis, for instance, is angled such that bipedalism is awkward (chimps do walk bipedally, just not naturally or easily). The angle of the illiac blade is what provides different muscle placement and center of gravity along with different rotation and flexion where the femur articulates with the pelvis.

    This sort of drastic evolution would be obvious in the fossil record. It isn't. It isn't present at all except in hominid lines going back through Ardipithecus (and so limited in this genus as to be debatable whether or not the hominid was truly bipedal).
    What are the names of the non-bipedal ancestors of chimps and gorillas? I need a link.

    Danke im Voraus (thanks in advance)
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    Quote Originally Posted by gottspieler
    Quote Originally Posted by SkinWalker
    Quote Originally Posted by Golkarian
    Isn't it unlikely? Since if chimpanzees and gorillas were descended from a biped ape they would have to gain that trait first, then lose it. Both processes requiring restructuring of the spine (curves to prevent shock) and the skull (movement of the neck entrance).

    Chimps and gorillas do not appear to be descended from a bipedal ape. All evidence points to the contrary.

    Moreover, chimp and gorilla anatomy is consistent with that of characters derived from earlier, non-bipedal ancestors. The chimp pelvis, for instance, is angled such that bipedalism is awkward (chimps do walk bipedally, just not naturally or easily). The angle of the illiac blade is what provides different muscle placement and center of gravity along with different rotation and flexion where the femur articulates with the pelvis.

    This sort of drastic evolution would be obvious in the fossil record. It isn't. It isn't present at all except in hominid lines going back through Ardipithecus (and so limited in this genus as to be debatable whether or not the hominid was truly bipedal).
    What are the names of the non-bipedal ancestors of chimps and gorillas? I need a link.

    Danke im Voraus (thanks in advance)
    I can tell you off the top of my head, but as far as "links" go, you may want to try talkorigins.org. I will, however, list a couple of texts that are excellent sources of information at the graduate and advanced undergraduate level of study.

    I would probably start with Proconsul, a quadrapedal primate of about 19 Ma. Some paleoanthropologists have a split after that with Sivapithecus giving rise to the orangutan line and Kenyapithecus giving rise to apes and humans.

    Others would follow this taxonomy: Proconsul --> Afropithecus --> Dryopithecus --> African apes / humans. With this taxonomy, Sivapithecus and Kenyapithecus split off from Dryopithecus at around 9 - 13 Ma and Kenyapithecus doesn't lead to the human line. The question then, is: does Kenyapithecus represent a species after the last common ancestor with hominids? That would put the LCA at Dryopithecus or, perhaps, some as yet undiscovered genus between them.

    What we have are a lot of fossils that can be dated with good accuracy, but there are many that are overlapping temporally and sometimes spatially, so it becomes the challenge for taxonomy to sort out the lineages. Sometimes this is very clear. Other times its very difficult, as it should be when looking at evolutionary splits, for the point of the split is necessarily blurred genetically and, therefore, the surviving fossils of skeletal remains look very similar. Taxonomy on skeletal remains is far more difficult than that of living animals since there are phylogenetic characters that simply will not preserve that will delineate species. There are many species of extant primates that cannot be differentiated from looking at skeletal remains alone, though we know that they are distinct, non-breeding populations of closely related species.

    Further Reading

    Klien, Robert (2009). The Human Career.

    Fleagle, John (1999). Primate Evolution and Adaptation.

    Koufos, George (2007). "Potential Hominoid Ancestors for Hominidae." In The Handbook of Paleoanthropology, Winfried Henke, Ian Tattersall, and Thorolf Hard (eds.).
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    Quote Originally Posted by Ophiolite
    As far as I am aware all specimens show a foum magnum that indicates bipedal walking, which in turn would preclude significant knuckle walking.
    What's a foum magnum?

    I want to learn the anatomy better as my pet theory depends on it. Pet is: we transitioned to bipedalism with aid of walking sticks. A staff or cane (literally) supports bipedalism where anatomy does not. That would show more as rapid changes in wrist and forearm, which could be mistaken for regression to branch-swinging or knuckle-walking.
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    I'm sure Ophi meant foramen magnum.

    http://en.wikipedia.org/wiki/Foramen_magnum
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    Much obliged.
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    foramen magnum
    One of the first cool anatomy terms I learned.
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    Quote Originally Posted by Pong
    Chimpanzees are further evolved from the LCA than modern humans. In that light it is more telling to say chimps evolved from humans than humans evolved from chimps... although neither is strictly true.
    What traits are 'more evolved'? I assume you mean have changed the most.
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    "More evolved" is a very loaded concept.

    One could say Pan troglodytes are "more evolved" than Ardipithecus, Sivapithecus, and contemporaries, from Proconsul. But this would be from the molecular clock scale.

    One couldn't say, for instance, that either Homo or Pan is more evolved than the other from the LCA since, by definition, they are equally evolved given equal amounts of time to allow for it.

    If, however, one were defining "more evolved" as the number of changes and adaptations that have occurred, then it would seem that the branch since the LCA which includes Homo would arguably be the winner of that hypothetical contest, but this is primarily due to the rich fossil record and the well-documented numbers of derived characters over the course of the last 4 to 10 million years, but particularly in the last 3 million years, that drive that conclusion. It could, however, very well be that there are just as many derivations in the Pan line that are simply not known since the common habitat for this clade is one that also doesn't provide good preservation (acidic soils of forest environs and such).
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    Quote Originally Posted by Golkarian
    Quote Originally Posted by Pong
    Chimpanzees are further evolved from the LCA than modern humans. In that light it is more telling to say chimps evolved from humans than humans evolved from chimps... although neither is strictly true.
    What traits are 'more evolved'? I assume you mean have changed the most.
    Apparently in comparing human and chimpanzee DNA there's a way to distinguish between adaptive mutations and background (neutral?) mutations, which I think are used as a baseline. Chimps have slightly more adaptive mutations than modern humans. I'm sorry I don't know more than that.

    So it doesn't point to specific traits. Chimps' DNA changes could have excluded walking anatomy, but that would be an assumption.



    Quote Originally Posted by Geo
    This is why I think the LCA speciation may involve cultural incompatibility. Plains tribes vs. forest tribes, etc. The forest guys became the chimpanzee. What assholes. Makes you want to club their brains out, don't it?
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    Quote Originally Posted by SkinWalker
    "More evolved" is a very loaded concept.
    a pity the cladistic terms plesiomorphy, synapomorphy and autapomorphy are such ugly words, because in fact they cover quite useful concepts, and are relatively free of the connotations that "more evolved" or "more advanced" carry
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    I believe that I happen to have been borne of a bicurious rape. My father was of the early Homo clan.
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    I like how pre-Darwinian Malay folk wisdom got a jump on science with "urang utan" literally "man of the forest".
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    I'm not sure what it means to have "the jump on science," but the orangutan, like all apes, has very familiar features to humans. It would be more surprising if they didn't see this species as something special.

    But they were clearly wrong. Orangutans aren't old men of the forest at all. They're very clever primates, but no closer to the human genus than chimps.
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    To name orangutan a kind of human would have been almost unthinkable before Darwin, I mean. Anyway I only said it to move the thread a notch. That's done.
    A pong by any other name is still a pong. -williampinn
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