To quote Mathew McConaughey from True Detective, " Nature created an aspect of nature separate from itself."

Starting with your last question - of course we are separate. Blind eyes can look at the world and see this. Humans can adapt to an environment and mold it to fit their needs. Goats cannot build a coal power plant any more than dolphins can create a nuclear submarine and defend themselves from hunters. Humanity is a part of nature but we are far different than wild animals. Please, let's not go down that road it is not productive.

"Eventually we will die off" - that is a view presented as fact, perhaps a good one to post here on CMV. I do think you are right in that many species have come and gone but that is given a natural cycle. Anthropomorphic intervention "skews" the rate of extinction too high, so there is not enough "replacement" species. As far as I know, there are no NEW species of rhino's or elephants being created to replace the ones that die off. Multiple countries are almost entirely devoid of wildlife, not even a deer to be seen.