Experience and observation lead to an entirely opposite conclusion. When we see the Anglo-Saxon of our days, although protected by all the resources of an advanced civilisation, subjected to the American conditions of life, and changed into a Yankee, we must admit that at each of his great stages, when man is submitted to new conditions of existence, he has had to harmonise himself with them, and in so doing undergo modification. Each of these principal stations has necessarily witnessed the formation of a corresponding race. The original characters, thus successively affected, have become more and more altered, by reason of the length of the journey, and the difference of conditions. When they have reached the end of their journey the grandchildren of the first emigrants would certainly only retain very few of the characters of their ancestors. The original human type has probably presented, for an indefinite time, its original characters in the tribes which remained fixed to the centre of appearance for our species. When the glacial epoch began, which, according to all appearance, made the earliest country of man uninhabitable, these tribes were forced to emigrate in their turn. Since that time the earth has no longer had _autochthones_, but has only been peopled by _colonists_. At the same time the modifying action of the conditions of life was felt by these last comers, who themselves were also transformed. From this moment, the original type of man has been lost; the _human species_ was only composed of _races_, all of which differed more or less from the first model. CHAPTER XXIII. FORMATION OF MIXED HUMAN RACES. I. The races which had been developed by the sole action of the conditions of life and of heredity, did not remain isolated. The earliest emigrants from the centre of appearance certainly did not pass at once to the extremity of the area determined by their first stages. They stopped on the way; they formed secondary centres, round which fresh emigrations spread. The history of the Lenni Lenapes, as of the Polynesians, proves that this must have been the case. Consequently, in many cases, the races first formed must frequently have come in contact. Then, as the waves of emigration followed each other, the last comers would meet on their way with those who preceded them. It will further on be proved that facts of this nature have occurred since Quaternary times. Whether peaceful or otherwise, these contacts would result in reciprocal penetrations, and consequently in _intercrossings_.