this post was submitted on 14 Nov 2023
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Yep, it's kinda fascinating. From what I've been told, human feet are actually pretty fucked up compared to the rest of mammals including other apes. Iirc, our feet first evolved to walk on tip-toes, like other mammals; then they evolved the ability to grab things, like apes, which came at the expense of our "back-knee" (which became our ankles). Then, as we started walking upright, our "hind-fingers" began merging and became toes, while the bones between the ankles and toes began lengthening again to give us a larger platform to stand on; and eventually we lost the opposable thumb-toes.
Tbh I kinda speculate that our arms are similar to our legs (tibia/fibula>humerus, femur>clavicle, scapula>pelvic girdle, shoulders>knees, elbows>ankles, etc). However, that suggests the ulna/radius should be somewhere in our feet, and I don't really see anything similar there.
Nah elbows correspond to knees. Shoulders correspond to the ball-and-socket part of the hip, humerus corresponds to femur, then ulna/radius correspond to fibia/tibula (yes you have two bones in your calves). There's no real correspondence to the flexibility of the scapula/clavicle in the hip (though the muscle groups are still pretty much the same if you ask any internal martial artist, it's just all fused and serves control of load distribution instead of "actual" movement).
Side note: Did you know that the five-way split (roughly) at ankle and wrist is evolutionarily very new? When you send orders like "stretch the index, curl the middle finger" that's not the orders travelling down the neural pathways, but "retract limb, index ignore that order" and "extend limb, middle (and others) ignore that order". That's kinda precisely the difference between gross and fine motor control and 99.9% of what you're doing in Taiji and the like is freeing the former from the tyranny of the latter. Also (albeit in a less holistic scale) when you learn to knit without cramping up, watch a capable grandma they're hardly moving their fingers at all.
Just different morphology to do different things.