Human selection has achieved visible changes in the outward appearance of domesticated animals in far less than a 100-year time span. Darwin pointed that out in his book. The Origin of Species postulated natural selection as an extension of HUMAN SELECTION, which was the introductory basis of his theory. He then went for several hundred pages, presenting a ream of evidence in wild animals and plants indicating they are subjected to the same process by the forces of nature, hence the term 'natural selection'. But as I said, human selection (selective breeding) was where he got the idea, and the word usage.