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I know how humans and flightless birds evolved bipedalism, but could life on land and so on evolve with bipedalism form the start? Try to think of something more than just two finned fish equivalents.

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closed as too broad by RonJohn, Ash, elemtilas, JBH, JohnWDailey Nov 11 '18 at 21:14

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  • $\begingroup$ What layout of two legs do you want, you can start with the mudskipper tripod, into something like an mexican mole lizard but this will likely never develop bipedalism. $\endgroup$ – John Nov 11 '18 at 15:06
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    $\begingroup$ The balance required for bipedalism is a heck of a lot harder than that required by quadrupedalism. Given that -- even now -- bipedal species are in the significant minority, "original bipedalism" is a non-starter. $\endgroup$ – RonJohn Nov 11 '18 at 15:07
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    $\begingroup$ "Try to think of something more than just two finned fish equivalents." Do my work for me. $\endgroup$ – RonJohn Nov 11 '18 at 15:08
  • $\begingroup$ The Anatomically Correct series would be an appropriate way to ask question - but it requires you to focus on a specific end-result (how do I rationalize X?). This is way too broad, especially since we don't completely understand evolution in the first place. Did bipedalism develop because some creatures wanted to live in trees all the time, or because some were inclined to tool building, or because they had to fight to fend off predators so often they started standing up? There's no way to justify one best answer. $\endgroup$ – JBH Nov 11 '18 at 16:53
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Perhaps a sea creature with forelimbs & tail starts elaborating its neck, such as did plesiosaurs. Gradually the animal moves into a mangrove environment and the limbs begin to function as grapplers thru tight spots, gradually lengthening, becoming weight-bearing, allowing the limbs to descend below the body cg.

You might then have something that could conceivably trundle about on the surface.

An unlikely scenario in the extreme, but its all I can come up with.

You might also think of some reason to inhibit quadrapediality from arising, since ergonomically that makes vastly more sense.

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The current scientific vision on the evolution of terrestrial animals it that they descend from a fish who first ventured on dry land ages ago. And a fish having generally four fins lead to all its descendants having four limbs.

evolution of land animals

If you want a bipedal ancestor to start from, you can tweak the story and, instead of having the Tiktaalik or the like, have a sort of seahorse move the first step on land.

Seahorses have already a vertical posture and can conveniently attempt to balance using their rear two fins and their tail. This may even lead to the atrophy of the two upper fins, resulting in no upper/front limbs for the descendants.

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    $\begingroup$ You'd probably need a longish period for the 'seahorses' (Aaffaffak? If you speak Inuktitut, please don't kill me :) to develop the right biomechanics. Legs positioned beneath the body's centre of mass, pelvis of the right shape, a balancing tail, a vertical spine supported by appropriate muscles. Perhaps a lifetime spent with fins>feet on the seafloor and the head just above the surface. What would be the incentive to live like that? $\endgroup$ – Tumbislav Nov 11 '18 at 10:11
  • $\begingroup$ I would say that a terrestrial Actinopterygian would be highly unlikely, simply due to their fins. $\endgroup$ – SealBoi Nov 11 '18 at 10:37
  • $\begingroup$ OK, a seahorse-like creature is a decent place to start. Thank you. $\endgroup$ – Joe Smith Nov 18 '18 at 4:06

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