Evolutionary Origin of Walking
It is theorized that "walking" among tetrapods originated underwater with air-breathing fish that could "walk" underwater, giving rise to the plethora of land-dwelling life that walk on four or two limbs. While terrestrial tetrapods are theorized to have a single origin, arthropods and their relatives are thought to have independently evolved walking several times, specifically in insects, myriapods, chelicerates, tardigrades, onychophorans, and crustaceans.
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