Charles Darwin was the first person to discover the most important mechanism of evolution, natural selection. One of his friends said "How extremely stupid not to have thought of that!"

Charles Darwin, the father of modern biology and the man who killed god.

Darwin got a lot of things right including the idea that the development of people (aka human apes) was not inevitable.

From Darwin and Natural Selection:

"Darwin did not believe that evolution follows a predetermined direction or that it has an inevitable goal.  His explanation that evolution occurs as a result of natural selection implied that chance plays a major role.  He understood that it is a matter of luck whether any individuals in a population have variations that will allow them to survive and reproduce.  If no such variations exist, the population rapidly goes extinct because it cannot adapt to a changing environment.  Unlike Lamarck, Darwin did not believe that evolution inevitably produces more complex life forms and that the ultimate result of this process is humans.  These were shocking, revolutionary ideas even for scientists who accepted evolution."

The variations (aka mutations) are "a matter of luck" but of course the natural selection of what works is not chance.

"Chance alone cannot explain the marvelous fit between individuals and their environment. And it doesn't. True, the raw materials for evolution--the variations between individuals--are indeed produced by chance mutations. These mutations occur willy-nilly, regardless of whether they are good or bad for the individual. But it is the filtering of that variation by natural selection that produces adaptations, and natural selection is manifestly not random. It is a powerful molding force, accumulating genes that have a greater chance of being passed on to others, and in so doing making individuals even better able to cope with their environment. It is, then, the unique combination of mutation and selection--chance and lawfulness--that tells us how organisms become adapted."
-- Jerry Coyne, University of Chicago biologist, author of Why Evolution is True