It depends on how rapidly a species reproduces. Bacterial evolution is quite visible in the lab. For other species where thousands of generations can take a long time, the evidence is in the fossil record -- as expected.
My complaint is with modern dogma. We must believe in evolution. We must not be racists.
You don't have to believe in evolution (or atoms, or relativity, or anything else that bothers you), and you can be a racist if you like.
One should reject racism for humanitarian reasons; it's just not nice to people. But it seems to me that a complete discussion of human evolution would include a discussion of race.
Darwin discusses the races of man extensively in The Descent of Man. And he concludes that we're all the same species. Interestingly, that wasn't a mainstream view in his generation.
Evolution today is a race between scientists striving to build a bigger, better, idiot-proof model of the history of life on Earth, and Nature trying to produce bigger and better idiots. So far, Nature is winning.