Being Human

Why do human beings so often see themselves as being radically separate from the rest of the "natural" world? I've seen this among both religious and secular people. Are the simple tools of primates or birds or raccoons or beavers less "natural" because they used natural materials for secondary goods? If all of that is still is considered "natural", why isn't all of human behavior likewise considered natural? What's at work here? I suspect this may have more to do with psychology than with theology or science.