When you consider the overlap between the almost human animals we know, our pets and those which demonstrate great cleverness and self-reliance, and those who are considered undeniably human but lack some of the characteristics we associate with normal thinking, it's hard to conclude that there is a hard and fast dividing line between them.
Add to that, we are going to eventually realize or admit that some of our cetacean or simian friends are not only close enough, but actually in the same category with us, or we may discover evidence for intelligent life elsewhere in our perusal of the universe, and it becomes clear that such a story would have to include every possibility which would allow growth and progress.
Your assignment, Mr. Phelps, is to diagram the above sentences.
Boy, do I know how to bring a thread discussion to a screeching halt!