Why do animals have four legs and humans have two?

Most animals from reptiles to mammals have 4 legs or limbs (even people). It's just that our front legs and front feet (our arms and hands) are specialized. Birds have very specialized front legs too (wings) as do bats (again, wings). Even though many animals have four legs and no hands doesn't necessarily mean they are worse off than us. Almost all four legged animals of about human size can run much faster and for a longer distance than we can. Ever try to catch a dog that doesn't want to be caught? If the dog is in reasonable shape, you won't be able to. Four legged animals have a longer stride than two legged people. The longer stride translates into a faster run than we can accomplish. On the plains of Africa, being able to outrun the lions or hyenas is pretty important, so most animals there run on 4 legs.