Humans, unlike most animals (except the gorilla, monkey, etc.) have opposable thumbs. A lot of animals don't have that characteristic. Since, humans have five fingers, they can do a lot of things like holding and building stuff. That's how we naturally survive. It is what makes us different from most animals. Also, humans walk on two legs and don't really have any natural feature that could protect them from harm ( like claws, sharp teeth, venom).
