Charles Darwin never thought he could witness evolutionary change. He relied instead on indirect clues. He looked at its effects after millions of years — in the fossil record and in the similarities and differences among living species. He got clues to the workings of evolution from the work of pigeon breeders, who consciously chose which birds could reproduce and thus created birds with extravagant plumage. But that was artificial selection — not natural selection that had been operating long before humans came on the scene. Darwin was pretty sure that natural selection worked too slowly for him or anyone else to witness.
Evolution in a Petri Dish