Darwin and evolution

Charles Darwin was born in Shrewsbury in 1809 and died in Bromley, Kent, in 1882, one hundred years ago. Darwin’s great contribution to human knowledge is contained in his book, The Origin of Species, which sets out a theory of organic evolution by natural selection.

Darwin had arrived at the theory of evolution as early as 1837 but proceeded no further with it until he found an explanation for the fact of adaptation. The solution occurred to Darwin when he read Malthus’s essay, The Principles of Population. It is a curious fact that Malthus’s mistaken view of population, which was to become the basis of Social Darwinism, prompted Darwin to develop his own theory. Indeed, we might say that Social Darwinism existed before Darwinism.

The theory of natural selection contends that all living things show a tendency to vary and that heritable variations (each of which may originate from one or more mutation) are transmitted from one generation to another. Those individuals affected by heritable variations, which give them a definite advantage over their fellows, will be more likely to survive in the struggle for existence and more likely to reproduce their kind. The less favoured individuals will tend to die out. Thus, in the course of many generations the species will tend to show a gradual change in the direction of a more favourable adaptation to its environment and a new species will emerge which is distinct from the original one.

With the knowledge and development of Mendelian genetics, the discovery of DNA, the development of molecular biology, and the formulation of the genetic code, the theory of natural selection has become sophisticated and is often termed as Neo-Darwinism. This theory has been subjected to a number of modern criticisms. For example, it has been argued that once species come into existence they persist for millions of years with little or no change (homeostasis). It has also been argued that when evolutionary changes do occur they are concentrated into relatively brief periods. The most recent criticisms of Neo-Darwinism have constituted a revival of Lamarckism: the theory that certain characteristics acquired during a parent’s lifetime can be passed on to the offspring. Darwin himself accepted this theory. It was the German biologist, August Weismann, who demonstrated the invalidity of Lamarckism. He showed that the hereditary substance—germ plasm—is transmitted from generation to generation without being influenced by bodily cells acquired during the individual’s lifetime. Modern research work by geneticists supports Weismann’s thesis. Claims have been made for cytoplasmic inheritance a non-molecular genetic mechanism in the cytoplasm (all the protoplasm excluding the nucleus). But it is now known that organells (specialised parts) of the cytoplasm (chloroplasto and mitochonaria) not only contain DNA, but also the machinery for transforming DNA into protein. Nevertheless, a number of experiments have been made, the success of which do not rule out the possibility of genetic mechanisms not dependent on the replication nucleic acids. Yet. as John Maynard Smith points out:

“It seems unlikely that they have been of major importance in evolution. The vast majority of inherited differences between organisms which have been analysed have turned out to be caused by differences between nuclear genes . . . The inheritance of acquired characters would lead to deterioration rather than evolution. On the other hand, homeostatic genes, resembling the self-correcting codes used for programming computers which always reverted to their original form after mutating, would make evolution impossible.” (The Theory of Evolution, p. 73)

None of the critics of Neo-Darwinism is arguing that evolution has not happened, but some of them are questioning the course it has followed. What is significant is not the way in which evolution has occurred, but the fact that it has occurred. We have only to refer to the fossil record to confirm its reality.

The most important qualitative event in the evolutionary process was the emergence of humanity. When physical evolution brought Homo Sapiens into being it gave rise to a unique organism. Humanity set in motion a new kind of evolution, which is not biological and established by inherited physical variations, but is social, cultural and technological. In social evolution, humanity makes itself by developing culture through successive stages. Nature transcended itself, so to speak, and created a being which is more than just a Naked Ape. Homo Sapiens is not merely an animal repeated, but is qualitatively something higher, something which has never existed before. Humans have an ability to think conceptually and this enables us to determine our own mode of existence.

H. WALTERS