BIOLOGICAL FOUNDATIONS OF SOCIOLOGY 535
depends on the variations of the individual members of the species; that is, on changes in the germ-plasm. A race evolves when it piles variations on variations during successive genera- tions. It is in this way that species undergo change during a state of nature. It is in this way that we improve our domesticated plants and animals.
Several theories have been formulated to account for the occurrence of variation, but they may all be placed in one of two categories. On the one hand, it is supposed that the variations of offspring are caused by changes in the environments of the germ-cells whence the offspring arise; on the other hand, it is supposed that they are not so caused, but arise " spontaneously." The first theory is very popular with medical men. Thus it is believed by them that, if a man leads a healthy, active life, his children will be innately stronger and more vigorous than they would otherwise have been; whereas, if he falls into ill-health through want, hardship, disease, dissipation, or some such cause, his germ-cells will be injured, and his offspring will tend to be innately inferior. A natural corollary to this hypothesis is a belief that a race will grow strong and vigorous if placed under conditions that benefit its individuals ; whereas it will degenerate if placed under opposite conditions. This belief, of course, is fundamentally opposed to the doctrine of natural selection, which supposes that races evolve only when placed under influences which, because injurious to the individual, weed out the weak and the unfit, and leave the race to the strong and fit.
We can easily test these opposing doctrines by noting what has happened to various races of men. Negroes on the west coast of Africa, for example, have been exposed for hundreds, perhaps thousands, of generations to severe malaria. This disease is caused by a microbe which invades the body in great numbers and floods it with a virulent poison, in which, therefore, the germ- cells are literally soaked. Practically speaking, every negro suffers for a prolonged period from malaria, and many perish of it. If ever the environment of the germ-cell causes variations in offspring, it should do so in this instance. But what do we find ? Neither the negroes nor any other races exposed to malaria
