Evolution.

Society for Experimental Biology

Date:: 1953

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

Credit: Evolution. Source: Wellcome Collection.

14/484 (page X)

$X FOREWORD tion and in the population from which they are drawn, and the selective advance or change in this average from one generation to another, which is usually a fraction of the differential, are important. Having thus defended my own rear, I pass on to summarize the contributions, Pringle boldly and appropriately opened with a discussion of the origin of life. His idea that the precursors of living organisms were systems of large volume in stagnant parts of the deep sea seems to me improbable. Some of my own speculations on this topic have achieved the stamp of orthodoxy in the Soviet Union, thanks to Oparin, and in the United States, thanks to Horovitz. I can assure Pringle that I am quite as sceptical about my own theory as about his. I hope, not only that he will develop it further, but that his example will induce others to 'stick their necks out'. When we have as many theories to choose from about the origin of life as we have about the origin of the planets, we shall be in a better position to choose one of them, or items from several. There is, however, a much more exciting possibility. Recent work on bacteria and viruses shows that one simple organism can incorporate and reproduce indefinitely constituents of another by processes which cannot be called sexual. It is therefore not inconceivable that two or more different sorts of life began independently, perhaps by Pringle's method and the Haldane-Oparin method, and that later organisms are derived from their concrescence. Baldwin and Medawar dealt with different aspects of biochemical evolution. Biochemical taxonomy goes back to Aristotle who, not having noticed Tubifex or Chironomus, defined what we now call vertebrates as red-blooded animals. We have not got much further than Aristotle because most simple kinds of organic molecule which occur in one species occur in many other species, and some in all species; while the larger molecules, which are specific to species, or even to genotypes within a species, have not been fully characterized. The universality of some biochemical con¬ stituents and processes is just as strong a support for the theory of evolu¬ tion as the universality of cellular and nuclear organization. Baldwin was lucky, or perhaps cunning, in finding a small molecule, creatine phosphate, which is present in all vertebrates and most chordates yet investigated and in some echinoderms, but is replaced by other compounds in other inverte¬ brates. But the reported finding of arginine phosphate in mammalian spermatozoa suggests that phosphagen may yet prove as inadequate a taxonomic label as haemoglobin. Medawar described the remarkable diversity of the antigens found in different members of one mammalian species, and the ways in which its$

Evolution.

Licence and re-use

Contents