The antagonism of conscious as opposed to natural selection[2] has now been in existence for many thousands of years, but it is only within the last century or less that the effect upon man’s constitution has become so marked that the danger of deterioration or decay has been thrust upon the attention, not only of scientific observers, but of the average, intelligent individual. No examination of history is necessary in this place to set out a reason for this comparatively sudden realisation of physical unfitness. Briefly, the civilisation of the past hundred years has been unlike the many that have preceded it, in that it has not been confined to any single nation or empire. In the past history of the world an intellectual civilisation such as that of Egypt, of Persia, of Greece, or of Rome, perished from internal causes, of which the chief was a certain moral and physical deterioration which rendered the nation unequal to a struggle with younger, more vigorous and—this is important—wilder, more natural peoples. Thus we have good cause for believing that the danger we have indicated, though as yet incipient only, was a determining cause in the downfall of past civilisations. But we must not overlook the fact that destructive wars and devastating plagues held sway in the earlier history of mankind, and whilst the latter acted as an instrument of evolution in destroying the unfit, the former, by decreasing the population, threw a burden of initiative and energy on the remnant, necessitating the use of active physical qualities in the business of all kinds of production. Now the conditions have altered. Greater scientific attainments in every direction than have ever been known have combated, and will probably in the future overcome the devastating diseases which have decimated the populations of cities, whilst a higher ethical ideal constantly tends to oppose the horrible and repugnant barbarism of war which, with the spread of civilisation even to the peoples of the Orient, becomes to our senses more and more fratricidal, a fight of brother against brother.