By Whit Gibbons One answer to the question of why no animals have evolved true wheels is that nature provides no dependable roads.
Some animals make their own roads.
Deer in the woods, muskrats in a marsh, and leafcutter ants through a tropical forest all leave their trails. But most natural trails are temporary, disappearing within a few seasons of being made. Human-made roads, in contrast, may last for decades or even centuries, and their impacts on a habitat surpass that of any other animal species. Human highways unquestionably have major environmental impacts on plants, animals, and habitats. Roads can change the direction of natural water flow, affecting the way wetlands function.