SACH-SAWCH

The idea is to get the center of mass on a flat uniform speed toward the goal. A===================================================== ======>B A=============================================>B /\_/\__/\_/\__/\_/\__/\_/\__/\_/\__/\_/\__/\_/\__/\_/\__/\_/\__/\_/\__/\_/\__ This is true even when A toward B is over bumpy ground. In a sense the big breakthrough was not the WHEEL but rather THE ROAD which allowed wheels to be worth the trouble to build. But the math – so to speak [control mechanism] needed to be quick. So, simplifying the movement of the center of mass over an irregular ground so that speed requirements would be effective needed a discard of the very flexible limb to body connections (slings of muscles as still exist in the fore limbs (arms) in trade for a connection which spatially does not move relative to the center of mass. The closer to that center the better. Tah-dah!!!! Nature invents articulated HIPS. No, not for 'walking'. No, not for speed either. Big nasty beasts were running all over the place, and plenty fast, eating everything slower moving or which pooped out while trying to escape from a fast hungry runner that didn't seem to tire. Hips simplification leg movement by giving up infinite this way & that way movement in trade for fixed center spherical action. This allows pendulum properties, the energy of one leg is more easily transferred to the other. The linkages below the hips adjust – on the fly – to inertial alterations – adapting to the irregularities of the ground. Wear & tear of impact is also reduced by having the last link (the foot) to be totally inertially adaptive working within a cone of expectation (of graded resistance). Deviations from expectation are SELF adjusted by [IMPORTANT] local (lower spinal cord) reflex arcs. For very big beasts the lower spinal cord was fat and were once called second brains as so many what-if immediate reaction patterns of correction were there – nearer to the needed circuits handling the hind foot details.