of variation. They do also give opportunity for the development of a new set of factors in evolution, the socio-psychical. It can not be too strongly emphasized, however, that these socio-psychic factors are conditioned by their' foundation in the innate qualities and capacities of human nature, that is, in the characters given to men by selection. It may be that the power of heredity is limited short of the powers of evolution and development. But this does not seem to be true for the higher moral qualities, nor for conspicuous intellectual power, though it is perhaps well to add the caution that heredity appears to be not yet thoroughly established for these qualities. But selection itself can make heredity more stable. It would be enough for the most Utopian sociologist if all human beings could be brought up and kept up, by the fixation of heredity, to the present highest level of intellectual power and moral character. So much progress selection may accomplish. Whether it does, depends on the adaptation of human institutions to such remote ends.
The question as to the applicability of natural selection to man can not be satisfactorily dealt with as one simple whole. Here as elsewhere analysis is the necessary instrument of science. By analysis we discover four distinct modes of selection: lethal, sexual, reproductive and group selection. We find, also, that these four forms have very different sorts of applicability in the explanation of man's evolution, past and present. Especially under present conditions it is reproductive selection that most calls for consideration.
In these days "race suicide" is a much talked of subject. There is plenty of occasion for the discussion. But the fact that attracts attention is not rightly called race suicide. Literally interpreted, race suicide is an absurdity. The actual fact that is attracting attention is a phase of reproductive selection. Its importance can hardly be exaggerated. But it can be truly evaluated only as seen in its setting as a phase of a form of selection. The fear of race suicide as a matter of quantity of population is no more valid or justifiable—it is rather far less justifiable—than the contrary and equally unanalytic fear of over-population awakened in Malthus and his followers a century ago. The question is not so much one of quantity, either by excess or deficiency, as of quality of reproduction and of population. It is therefore a question of selection. In this matter of selection in mankind it is doubtless true that "race suicide"—if the term means the self-elimination of certain classes of members of society—now plays the most significant part.
