As for the other nations ranging from Lapland to the Mediterranean, classical history, although it does not go back a great distance in point of time, is a sufficient proof that crossings are the inevitable result of invasions, wars, and political and social events. Asia presents, as we know, the same spectacle; and, in the heart of Africa, the Jagas, playing the part of the hordes of Gengis-Khan, have mixed together the African tribes from one ocean to the other. XI. I need scarcely allude here to the general facts which follow from the detailed history of races. Short though it be, this appeal to the reader’s memory will, I hope, give a sufficient motive for the following conclusions. Conditions of life and heredity have fashioned the first human races, a certain number of which, on account of their isolation, have been able to preserve for an indefinite time this first characteristic. Perhaps it was during this very distant period that the three great types of the Negro, the Yellow, and the White were characterised. The migratory and conquering instincts of man have brought about a meeting between these primary races, and consequently a crossing between them. Since the appearance of mixed races, crossing itself has only acted under the domination of the conditions of life and heredity. The great movements of nations have only taken place at long intervals, and as it were form so many crises. In the interval between these crises, the races which have been formed by the crossing have had time to settle and become uniform. The consolidation of the mixed races, the relative uniformity of characters effected by the crossing, have taken place very slowly, in consequence of the absolute want of selection. Consequently every mixed race which has become uniform is also very ancient. Human instincts have produced the mixture of mixed races, just as they have produced that of the primary races. Every mixed race, when uniform and settled, has been able to play the part of a primary race in fresh crossings. Mankind, in its present state, has thus been formed, certainly for the greatest part, by the successive crossing of a number of races at present undetermined. The most ancient races which we know, the quaternary races, are still represented in our own days, either by populations generally small in number, or by isolated individuals, in whom atavism reproduces the characters of our remote ancestors. This is a fact which will be proved further on. CHAPTER XXIV. INFLUENCE OF CROSSING UPON MIXED HUMAN RACES. I. Has the crossing of human races been, or will it be, advantageous or detrimental to the species considered as a whole? The followers of Morton in America, and of MM. de Gobineau and Perrier in France, have stated that human crossing had, or would have in the future, disastrous consequences. Has this opinion any foundation? Let us study the facts.