Can natural selection explain all known adaptations?
Complex adaptations The question is important historically, and it often still arises in popular discussions of evolution. The case against selection would run something like this: There is no doubt that natural selection explains some adaptations, such as camouflage. However, the adaptation in this case, as well as in other famous examples of natural selection, is simple. In the peppered moth it is simply a matter of adjusting external color to the background. The problem arises in complex characters, which are adapted to the environment in many interdependent respects. Darwins explanation for complex adaptations is that they evolve in many small steps; that is what Darwin meant when he called evolution gradual. Evolution has to be gradual because it would take a miracle for a complex organ, requiring mutations in many parts, to evolve in one sudden step. If each mutation arose separately, in different organisms at different times, the whole process is more probable. Darwins gradualis
