In his masterwork Ecological Genetics, Ford (1964) wrote: ‘One of the most far-reaching results of recent work on ecological genetics is the discovery that unexpectedly great selective forces are normally operating to maintain or to adjust the adaptations of organisms in natural conditions ... That consideration forces us completely to readjust our thoughts on evolution and to recognize that a population may adapt itself very rapidly to changed conditions.’ Indeed, the readjustment is a radical one: whereas the pioneers of evolutionism were concerned to prove by indirect evidence that evolution did in fact happen, we are facing the challenge to observe it actually happening, to investigate the causes that bring particular evolutionary events about, and even to reproduce or deliberately alter their course experimentally.