I have said above that the discoveries of M. l’Abbé Bourgeois testify, in my opinion, to the existence of a _tertiary man_. But everything seems to show that as yet his representatives were but few in number. The Quaternary populations, on the contrary, were, at least in distribution, quite as numerous as the life of the hunter permitted. Are we justified in imagining that during the Tertiary period man lived in polar Asia side by side with those species which I have just mentioned, and that he supported himself by hunting them as he afterwards did in France? The fall of temperature compelled the animals to migrate southwards; man must have followed them to find a milder climate, and to be within reach of his customary game. Their simultaneous arrival in our climates and the apparently sudden multiplication of man would thus be easily explained. The centre of human appearance might then be carried considerably to the north of the region I have just been discussing. Perhaps prehistoric archæology or palæontology will some day confirm or confute this conjecture. However this may be, no facts have as yet been discovered which authorise us to place the cradle of the human race elsewhere than in Asia. There are none which lead us to seek the origin of man in hot regions either of existing continents, or of one which has disappeared. This view, which has been frequently expressed, rests entirely upon the belief that the climate of the globe was the same at the time of the appearance of man as it is now. Modern science has taught us that this is an error. From that time there is nothing against our first ancestors having found favourable conditions of existence in northern Asia, which is indicated by so many facts borrowed from the history of man, and from that of animals and plants. BOOK V. PEOPLING OF THE GLOBE. CHAPTER XVI. MIGRATIONS BY LAND.—EXODUS OF THE KALMUCKS FROM THE VOLGA. I. At the point which we have now reached, the connection of facts and of their consequences proposes a fresh problem. Physiology has proved that there exists but _one species_ of man, of which the human groups are races. Zoological geography has taught us that this species was originally localised in a relatively very limited space. It is now met with everywhere, because it has spread by irradiation in every direction from this centre. The _peopling of the globe by migrations_, is the necessary consequence of the preceding facts. Polygenists, and the partisans of the autochthony of nations have declared that these migrations are _impossible_ in a certain number of cases, and have brought forward this pretended impossibility as an objection to the doctrine which I uphold. Here, again, I turn to facts for my answer.