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outboxtheside t1_iwpdmss wrote

From a study comparing the genus Pan (chimpanzees and bonobos) with the genus Gorilla: https://www.pnas.org/cms/10.1073/pnas.0901280106/asset/e2b630b0-6d75-4240-a8be-4638c59efab8/assets/graphic/zpq9990990910003.jpeg

If you're looking for a visual.

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bwyer t1_iwpyknb wrote

Thank you.

Of course, I was promptly forced to recreate the position with my own hands to really figure out what was going on. The diagrams were quite helpful.

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sticksnstone t1_iwq21z0 wrote

So the "arm" of the gorilla is stiff while that of the chimp is bent at a joint.

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mtx013 t1_iwqa2bs wrote

Thats not an arm, the image shows a profile picture of wrist/hand/fingers, but your point stands.

For reference, use your own anatomy: the bone they use to touch the ground is the middle bone of your fingers (thumb excluded) and the finger tip is curled up. From there we have the finger first bone (slightly bent), hand bone (big one), two wrist bones and just the end end of forearm bone.

The main difference between the two species is how the forearm-wrist, wrist-wrist and wrist-hand articulations are used. Chips bend them and gorillas use then in a straight line.

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