Another and much more plausible argument has been advanced: In the wild state living species do perfect themselves by means of natural selection. Human society by caring for the imperfect and defective individual has eliminated natural selection. Therefore further mutations will not improve mankind. It is very hard to discuss this question for the simple reason that the argument involves the interaction of two processes extremely different in magnitude and in fact different in kind. On the one hand it concerns itself with evolution which proceeds in the slow deliberate way of a glacier. On the other hand it focuses attention upon the process of human civilization with its technical and social changes which has gained momentum like an avalanche. The momentum is still there and it is still increasing and where we shall land we do not know. To consider the motion of the glacier while being carried along by the avalanche puts things completely out of proportion. Long before the present rates of mutation could have any effect upon the human species we shall live in a very different world and we shall have started to influence our own behavior including those of selection, natural or otherwise, in ways which today we cannot foresee. If we discuss the question how civilization will influence natural selection, we shall not do it with the hope of arriving at a firm answer. We shall do it rather in order to illustrate how doubtful all the arguments are which concern the interplay of two processes which cannot be measured in the same scale. It is true that we can and do preserve the lives of children who, because of inherited weaknesses, would perish under natural conditions. It is true too that we do this for reasons and for feelings concerning the individual and we do it without regard to the consequences to the race. However, under our present condition of civilization a disease which can be corrected by administering chemicals or using the surgeon’s knife is no longer effectively a disease. In our present condition such a life can be as valuable to society and to the race as a life which does not have these superficial shortcomings. That we can and do preserve more life in this manner only emphasizes that under present conditions biological differences which used to be important no longer matter.