A natural selection

R.A. Fisher, in his 1929 book The Genetical Theory of Natural Selection, noted that Charles Darwin believed in the theory of blending inheritance, and that this conditioned his views on variation and therefore on theories for the possible causes of evolution. Darwin realized that blending, or fusion, inheritance reduces variation and that all variability must be continually at work, or else natural selection would have nothing to act upon. Thus, blending inheritance forced Darwin and others to attach great importance to hypothetical means of producing variability or, as we would see it now, there was a need for mutations to be arising all of the time, to defeat the inevitable regression to homogeneity. Darwin and his contemporaries were all Lamarckians. The arch-Lamarckian was, of course, Lamarck himself, who thought it was enough for animals to want to change and that the right mutations would be produced to satisfy these desires in their progeny. Darwin thought it was the adaptive changes themselves that triggered the mutations; others postulated evolutionary forces that acted from the outside, or intrinsic urges in organisms themselves. It was Mendel’s discoveries that dispelled all of this nonsense. Most people remember him for his laws of segregation, but it is his theory of particulate inheritance that provided the fundamental basis for evolution by natural selection, and that enabled natural selection to be studied, not as the junior partner in Darwin’s theory, but as the central agency working with particulate inheritance. As everybody knows, Mendel’s discoveries lay neglected and unknown until their rediscovery 100 years ago this year. I have gone into all of this because I become more and more conscious that most people do not understand evolution by natural selection. As direct evidence, I offer the following. A few months ago, an old friend, Jack Dunitz, reminded me that in 1994 I had signed a circular letter to do with journal publication, following which he had written to me under a pseudonym and that I still owed him a reply. I have no memory either of the circular or of receiving his letter. However, he was good enough to forward me a copy of his letter, and I reproduce it here together with my belated reply. R355