It is generally accepted that evolutionary changes are slow. This concept was crucial for Darwin’s ideas about natural selection (the idea that vast amounts of time were required was advocated by Charles Lyell in his ‘Principles of Geology’, which Darwin read during his voyage on the Beagle). If our conception of evolution is correct, the same kinds of processes that drove evolution in the past should be going on in our own time, just as the geological forces of erosion, volcanic eruptions, and tectonic changes continue. The rates of these processes may vary from one organism to another and in different locations. We are usually unable to detect these changes, either for lack of suitable markers or because they are too slow relative to our lifetime. But some such changes are fast enough to be detectable, and may help us to understand those that are not.