Evolution.

Society for Experimental Biology

Date:: 1953

Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Evolution. Source: Wellcome Collection.

16/484 (page XII)

xii FOREWORD Kendall's paper dealt with the mathematics of mutation and selection in bacteria. Once again the time scale is so short that its relevance to evolution is problematical. But certainly the questions which he put, and partially answered, need an answer. Willmer's and S. Manton's contributions dealt with the evolution of two functions, vertebrate photoreception and arthropod locomotion. In each case it seems that a limited number of possibilities were open and that each has been exploited by several different groups. The evolutionary implica¬ tions of functional anatomy demand a vast amount of study, for which such papers as these lay a foundation. Chance and Mead dealt with an episode in the evolution of behaviour, and Spurway also devoted some space to this topic. It is bound to be speculative, because we can deduce less about the behaviour of extinct species than about their vision, and much less than about their locomotion. While I suspect that arboreal life was the main factor influencing the course of primate cerebral evolution. Chance and Mead show that their social structure cannot be neglected as an influence. A group of contributions, including those of Demerec, Mather, Ponte- corvo (unfortunately not printed) and Waddington, dealt with general problems of genetics. Demerec's paper is complementary to that of Hinshelwood. I at least am convinced that chemical substances, including very simple ones such as manganous chloride, induce heritable changes in bacteria which are not generally adaptive, and which we call mutations. If I were a dictator (which heaven forbid), I should force each of Demerec and Hinshelwood to work for three months under the other's direction, in the hope of effecting some kind of synthesis. I hope that this symposium will have had the effect of at least inducing them to exchange pupils. I fear that it has not. Demerec's paper is extremely interesting from the bio¬ chemical point of view, but it is not clear to me that a ten-thousand-fold increase in the rate of mutation at a locus, say from io~^ to io~®, will have much evolutionary effect on bacteria, though it might well have one on a metazoan or metaphytan species whose total number was less than a million. Mather's paper on the whole represents the views of the majority of geneticists on the structure of populations and on the evolutionary process. Just because it does so it is a particularly valuable and, if I may use the word, unselfish contribution to the discussion. The sections which deal with the effect of linkage, and the importance of heterochromatin, contain theories for which he is personally responsible and which are widely, but not universally, shared. The difficulty, which he points out, of distin¬ guishing between single genes and groups of closely linked genes acting