Look closely at the picture below - there are two pigeons who tend to roost outside my window, on a rooftop below. Note that rather than the dull grey of the common Istanbul (or London, or New York, or San Francisco) pigeon, these birds are rust-coloured, matching almost exactly with the colour of rooftop tiles in my neighbourhood. Clearly, this a phenotypic expression of an adaptation that has been selected for by the pigeons' environment. What is interesting to me is the evolutionary time-scale: I'm reasonably certain that these tiles have been used in our area for a mere few hundred (as opposed to thousands) of years. Within this relatively short time period, over generations, a random mutation which conferred a marginal reproductory advantage was successfully selected.

The evidence for Darwin's theory is literally right outside one's window.