Irreducible Complexity.

[Darwinian]

All back boned animals are directly evolved from very early fish, including of course, todays fish. The lungfish, or rather something like it, would have preceded snakes as a snake is basically a lizard that has lost it's limbs.

We can trace our ancestry back through mammals, mammal like reptiles, reptiles, fish and so on.. The snake took the same route as us until it got to reptiles and that's when we went out different ways.