The spread of Western and Christian civilisation all over the world, during the last four hundred years, has been marked, on all continents, by the disappearance of large numbers of technically less advanced peoples, or by their numerical regression, which in turn was accompanied by the decadence and crumbling of their cultural inheritance. But such feats of extinction are not the prerogative of the white man of modern civilisation. Every point on the globe, at all times, has witnessed struggles for life, where victory went to the stronger. The extinction of Neanderthal man, some thirty thousand years ago, was probably due to the appearance of Cro-Magnon and Chancelade man, who entered Europe at that time and had attained a more advanced technical civilisation than their predecessors. In historic times, we know of several cases in which peoples were driven back and annihilated by neighbours whose civilisation was more advanced and who were endowed with a greater expansive force. The Negritos of South-east Asia had been ousted from a part of their original territory by the Malayans and Chinese long before the arrival of the Europeans. Several Melanesian tribes were exterminated in the course of the ancient Polynesian migrations. These examples could be multiplied. They are in fact so numerous that it has become customary to consider them almost as manifestations of a biological necessity, against which human will remains impotent.