Something else that occurred to me this afternoon is the importance of processes. Species variation through genetic selection is a process, which has been known about for centuries, because it is used in selective breeding. Darwin’s (and Wallace’s) insight was to see how this could happen naturally through competition for resources. The greenhouse effect is a recognised process, the physical relationships by which the concentration of some gases in the atmosphere keeps the sun’s heat around the planet are also well understood. Once we understand the processes, we can make predictions which can be tested by observation.

There is a tendency among those trying to discredit scientific theories to start from observations and try to find alternative explanations for them. But if the processes which generate those observations are already understood, it is perverse to try to ignore those processes, unless there are very sound reasons to do so. Given that we know that inbreeding within groups will generate different characteristics when it comes to breeding dogs, why should we assume that this would not apply to the development of different characteristics in populations of finches on different islands? Given that we understand the greenhouse effect, why should we assume that the warming which has been predicted for decades and is now being observed has another explanation?