Other facts show clearly that the fauna and flora of the present world find themselves in a period of recoil with regard to their modification. In the tertiary period the fauna and flora of the world were richer than to-day; many more older species have disappeared than new ones have arisen. This fundamental fact seems due to the extremely slow cooling of the earth, and appears to be indicated by the powerful growth in tropical climates, the fauna and flora of which resemble those of the tertiary period, and, on the other hand by the relative poverty and slowness of growth in cold countries.
Conclusions.—What are the principal conclusions to which we are led by this short study of the ancestral history or phylogeny of man?
(1). The transformation or evolution of living beings is a demonstrated fact.
(2). The factors in evolution appear at first sight to be very diverse: selection, mutation, climatological, physical and chemical factors, etc.
We have seen that they may all be connected with the fundamental principle of mnemic engraphia, aided by natural selection. No doubt the nature of the mnemic engraphia of external agents in the living substance is still unknown. When we are able to connect the laws of life with the laws of inert nature, we shall only have before us a single great metaphysical mystery, that of the tendency of mundane energy to the differentiation of details and the production of complicated forms. What is important here is to know that engraphia and selection are capable of considerably modifying species in a positive or negative manner, for good or evil, improving them by good influence and good conjugations, or deteriorating them by bad selection or by blastophthoria, which causes them to degenerate. The combination of a bad selection with blastophthoric influences constitutes the great danger for humanity, and it is here that a rational sexual life should intervene.
(3). The mental faculties of animal species, as well as their physical characters, depend on their ancestral hereditary mneme. They simply represent the internal or introspective side of central activity, and the brain obeys the natural laws of the mneme in the same way as the other organs.
(4). It follows from all this that phylogeny and selection, the same as heredity properly understood, have the right to a fundamental place in the sexual question, for the germs which, after each conception, reproduce an individual are, on the one hand, bearers of the inherited energy of our ancestors, and on the other hand, that of future generations. According to the care or neglect of civilized humanity they may be transformed for good or evil, progress or recede. Unfortunately, owing to religious and other prejudices, the question of evolution is not discussed in schools. Hence, the majority of men only hear of these things by hearsay in a rough and inexact manner; so that a series of phenomena familiar to naturalists and medical men, are still dead letters for the rest of the public. This obliges me to speak further on some points of detail.
The so-called historical times, that is the times of the Chinese, Egyptians and Assyrians, which appear to us extremely remote, are from the point of view of evolution very near to us. These ancient peoples, at any rate those who were our direct ancestors, or who were closely related to them, are thus, in the language of evolution, which takes no count of time or of the number of generations, our very near relations. The generations which separate them from us and the few hundred generations between them and those of their direct ancestors, who were at the same time ours, represent a limited period from the point of view of the ethnological history of mankind.
On the other hand, if we examine the savage peoples of America, Asia, Africa and Australia, which have been specially studied since the discovery of America and some of which are actually living, and compare them with ourselves and with our ancestors of four thousand years ago, we find that they differ infinitely more from us than we differ from our ancestors, as their ethnographical and historical remains are sufficient to prove.
Among the savage peoples we find races such as the pigmies of Stanley (Akkaas), the Weddas of Ceylon, even Australians and negroes, whose whole bodily structure differs profoundly from our European race and its varieties. The profoundness and constancy of these differences clearly show that the relationship of such races to ours must be very remote. We are concerned here with veritable races or sub-species, or at least with very constant and accentuated varieties. It is true that it is difficult to unravel the almost inextricable confusion of human races; but we may be certain that the savage races and varieties remote from ours, and even certain less-remote races such as the Mongols and Malays, are, phylogenetically speaking, infinitely less related to us than the ancient Assyrians. This indicates that the ancestors which were common to us and these races must probably be looked for several thousands of generations back, even when their descendants are still living on other continents at the present day.