Sociology and Modern Social Problems | Page 9

of animals nearest man. This is only one of the many bearings which Darwin's theory has upon the study of social problems; but it is evident even from this that it revolutionizes sociology. So long as it was possible to look upon human society as a distinct creation, as something isolated, by itself in nature, it was possible to hold to intellectualistic views of the origin of human institutions.
But some one may ask: Why should the sociologist accept Darwin's theory? What proofs does it rest upon? What warrant has a student of sociology for accepting a doctrine of such far-reaching consequences? The reply is, that biologists, generally, during the last fifty years, after a careful study of Darwin's arguments and after a careful examination of all other evidence, have come substantially to agree with him. There is no great biologist now living who does not accept the essentials of the doctrine of descent. Five lines of proof may be offered in support of Darwin's theories, and it may be well for us, as students of sociology, briefly to review these.
(1) The homologies or similarities of structure of different animals. There are very striking similarities of structure between all the higher animals. Between the ape and man, for example, there are over one hundred and fifty such anatomical homologies; that is, in the ape we find bone for bone, and muscle for muscle, corresponding to the structure of the human body. Even an animal so remotely related to man as the cat has many more resemblances to man in anatomical structure than dissimilarities. Now, the meaning of these anatomical homologies, biologists say, is that these animals are genetically related, that is, they had a common ancestry at some remote period in the past.
(2) The presence of vestigial organs in the higher animals supplies another argument for the belief in common descent. In man, for example, there exist over one hundred of these vestigial or rudimentary organs, as the vermiform appendix, the pineal gland, and the like. Many of these vestigal organs, which are now functionless in man, perform functions in lower animals, and this is held to show that at some remote period in the past they also functioned in man's ancestors.
(3) The facts of embryology seem to point to the descent of the higher types of animals from the lower types. The embryo or fetus in its development seems to recapitulate the various stages through which the species has passed. Thus the human embryo at one stage of its development resembles the fish; at another stage, the embryo of a dog; and for a long time it is impossible to distinguish between the human embryo and that of one of the larger apes. These embryological facts, biologists say, indicate genetic relation between the various animal forms which the embryo in its different stages simulates.
(4) The fossil remains of extinct species of animals are found in the earth's crust which are evidently ancestors of existing species. Until the doctrine of descent was accepted there was no way of explaining the presence of these fossil remains of extinct animals in the earth's crust. It was supposed by some that the earth had passed through a series of cataclysms in which all forms of life upon the earth had been many times destroyed and many times re-created. It is now demonstrated, however, that these fossils are related to existing species, and sometimes it is possible to trace back the evolution of existing forms to very primitive forms in this way. For example, it is possible to trace the horse, which is now an animal with a single hoof, walking on a single toe, back to an animal that walked upon four toes and had four hoofs and was not much larger than a fox. It is not so generally known that it is also possible to trace man back through fossil human remains that have been discovered in the earth's crust to the time when he is apparently just emerging from some apelike form. The latest discovery of the fossil remains of man made by Dr. Dubois in Java in 1894 shows a creature with about half the brain capacity of the existing civilized man and with many apelike characteristics. Thus we cannot except even man from the theory of evolution and suppose that he was especially created, as Alfred Russel Wallace, Darwin's contemporary and colaborer, and others, have supposed.
(5) The last line of argument in favor of the belief that all existing species have descended from a few simple primitive forms is found in the fact of the variation of animals through artificial selection under domestication. For generations breeders have known that by carefully selecting the type of animal or plant which they have desired, it is possible to produce approximately that