退一步'地'阔天宽

The theory on the evolution of land animals goes like this: Some ancient fishes developed limbs to get out of water when predators are closing on them, an evloved trait as a way to evade their predators. These ancient fishes in turn found the land a whole new world to survive. Well, these losers running away from their dangerous water habitat are the so-claimed common ancestor of all land animals.