Page:Popular Science Monthly Volume 3.djvu/618

602, is undeniable. Chinese are recognizable as Chinese in whatever part of the globe we see them; every one assumes a black ancestry for any negro he meets; and no one doubts that the less-marked racial varieties have great degrees of persistence. On the other hand, it is unquestionable that the likenesses which the members of one human stock preserve, generation after generation, where the conditions of life remain constant, give place to unlikenesses that slowly increase in the course of centuries and thousands of years, if the members of that stock, spreading into different habitats, fall under different sets of conditions. If we assume the original unity of the human race, we have no alternative but to admit such divergences consequent on such causes; and, even if we do not assume this original unity, we have still, among the races classed by the community of their languages as Aryan, abundant proofs that the subjection to different modes of life produces, in course of ages, permanent bodily and mental differences: the Hindoo and the Englishman, the Greek and the Dutchman, have acquired undeniable contrasts of nature, physical and psychical, which can be ascribed to nothing but the continuous effects of circumstances, material, moral, social, on the activities, and therefore on the constitution. So that, as above said, one might have expected that biological training would scarcely be needed to impress men with these cardinal truths, all-important as elements in sociological conclusions.

As it is, however, we see that a deliberate study of Biology cannot be dispensed with. It is requisite that these scattered evidences, which but few citizens put together and think about, should be set before them in an orderly way; and that they should recognize in them the universal truths which living things at large exhibit. There requires a multiplicity of illustrations, many in their kinds, often repeated and dwelt upon. Only thus can there be produced an adequately-strong conviction that all organic beings are modifiable, that modifications are inheritable, and that therefore the remote issues of any new influence brought to bear on the members of a community must be serious.

To give a more definite and effective shape to this general inference, let me here comment on certain courses pursued by philanthropists and legislators, eager for immediate good results, but pursued without regard of these biological truths which, if borne in mind, would make them hesitate, if not desist.

Every species of creature goes on multiplying till it reaches the limit at which its mortality from all causes balances its fertility. Diminish its mortality, by removing or mitigating any one of these causes, and inevitably its numbers increase until mortality and fertility are again in equilibrium. However many injurious influences are taken away, the same thing holds, for the reason that the remaining injurious influences grow more intense. Either the pressure on the