Since animals are more primitive than ancient humans, they don't possess useless organs or also referred to as vestigial organs. Each and every organ has its own important function. Instead, some of the organs are either poorly situated in the animal's body to perform specific tasks and therefore, considered as vestigial organs. For example, pythons and boa constrictors have tiny hind leg bones buried in their muscles toward their tail ends but snakes don't walk instead, they crawl.