What use are paralyzed legs or uncontrollable stubs? How did legs get their start? Many animals don’t have legs. But if prototype legs worked well enough to confer a small advantage for an animal to get closer to food or to escape a predator, then it doesn't matter how small and un-leglike the first legs were. However slight an improvement can be, it can make the difference between life and death. Natural selection will then favour slightly better, prototype legs. When these inefficient legs have become the norm, then a slight further increase in leg functionality will make the difference between life and death. And so on, until we have proper legs. See Richard Dawkins, The Blind Watchmaker, pp. 89-90.