To nearly everybody it seems perfectly natural to assume that snakes have always looked much like the slender, tubular animals they are today, although in fact the members of this most recently evolved of the reptile groups achieved their current form only after an elaborate physical restructuring. For nearly 60 million years their predecessors ran around as four-legged terrestrial animals similar to contemporary monitor lizards, until, early in the Cretaceous Period, they gradually abandoned their limbs in favor of an attenuated physical form suited to a radically different way of life . . .

In the darkness of their subterranean burrows, the [proto-snakes] came to depend mostly on smell and taste – senses combined in the specialized forked tongues they had already evolved . . . Since wriggling worked better than walking in narrow underground tunnels, their limbs shrank into fetuslike stubs, and as their bodies gradually extruded into the serpentine form of modern snakes, little by little they ceased to be lizards at all. [2187]