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| delsydebothom |
 Posted: Mon Mar 08, 2010 9:11 am Post subject: 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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| KALSTER |
| Posted: Mon Mar 08, 2010 9:22 am Post subject: Re: Might Chimps and Gorillas be the descendants of a biped |
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| delsydebothom wrote: |
| 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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| delsydebothom |
| Posted: Mon Mar 08, 2010 9:50 am Post subject: Re: Might Chimps and Gorillas be the descendants of a biped |
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| KALSTER wrote: |
| delsydebothom wrote: |
| 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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| dupont |
| Posted: Mon Mar 08, 2010 10:41 am Post subject: |
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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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| Pong |
| Posted: Tue Mar 09, 2010 2:51 am Post subject: |
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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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| marnixR |
| Posted: Tue Mar 09, 2010 5:27 am Post subject: |
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why yes for the chimp but no for the gorilla ?
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| SkinWalker |
| Posted: Tue Mar 09, 2010 7:31 am Post subject: |
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| Pong wrote: |
| 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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| marnixR |
| Posted: Tue Mar 09, 2010 9:50 am Post subject: |
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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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| Pong |
| Posted: Tue Mar 09, 2010 2:59 pm Post subject: |
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| marnixR wrote: |
| 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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| SkinWalker |
| Posted: Tue Mar 09, 2010 9:34 pm Post subject: |
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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.
| Quote: |
| 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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| Pong |
| Posted: Wed Mar 10, 2010 1:23 am Post subject: |
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| SkinWalker wrote: |
| 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.
| SkinWalker wrote: |
| Quote: |
| 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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| Golkarian |
| Posted: Wed Mar 10, 2010 11:00 pm Post subject: |
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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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| Pong |
| Posted: Wed Mar 10, 2010 11:14 pm Post subject: |
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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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| marnixR |
| Posted: Thu Mar 11, 2010 12:18 am Post subject: |
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what's wrong with saying "shared a common ancestor" ?
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| SkinWalker |
| Posted: Thu Mar 11, 2010 12:49 am Post subject: |
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| Golkarian wrote: |
| 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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