When a race slowly migrates south it undergoes an enormous evolution of new physical characters to fit it to the new climate, and it does this by the same law of selection. Hence, the present descendants may not resemble the original European ancestor at all, and they give us no certain knowledge of the successive stages of our own evolution. The two African anthropoids, chimpanzee and gorilla, for instance, have long heads and are evidently descended from the earliest emigrants, but may not resemble our common ancestor at all. Likewise, the lowest race in Africa, the monkey, like pygmies described recently by Sir Harry Johnston, are probably descendants of the earliest human arrivals in Africa, and, as Johnston correctly assumes, they were forced into the most inhospitable forests by brainier later arrivals. They, too, have been so changed physically to fit them to their life that they must be much different from their European ancestor. In the same way, selection has adjusted the broad-headed Asiatic invaders of Europe so that they have become white skinned, and as they have learned Aryan languages, they have until recently been considered to be Aryan invaders, and have been incorrectly named the Celto-Slavic race.
It might be added in explanation that the head preserves its general shape through all changes of environment, and it is the best test of racial relationships anthropologists have yet discovered. It survives for untold thousands of years, and this is why we are so sure that there is a common origin of such widely departed types as African pygmies and Baltic man. Perhaps, even, there is a connection between Australians at one extreme and the ancient long heads of the British Islands at the other.
The causes of the origin of the two-head types, long and broad, are not known, but it is surmised that it was due to some very early environment making it necessary for the prehuman Eastern species to have a broad body, neck, head, face, limbs, etc., while the Western type had long slender parts, the skull in each case partaking of the general form. Probably one was a meat eater and lived on the ground and needed a heavy body, while the other was a vegetarian and a tree dweller, needing a light, slender body for climbing - but it is all speculation. Body changes can occur later while not affecting the skull, whose actual shape is immaterial as far as existence is concerned. Thus, of the two broad-headed anthropoid offshoots of the Eastern type, gibbon and orang-outang, one is very slender and the other thick set. Likewise, we now have slender and thick-set long-headed races as well as both types of broad-headed races. Skin color is a secondary matter, as we will later explain. Recently there has been a reaction against the idea that head shape is the best test of racial affinities, Prof. Wm. Ridgeway* going so far as to assert that the environment may change the skull. Until we find the reasons for such shapes discussion is futile. The only thing we need know here, is the fact that by heredity, the shape is retained for immense periods.