We shall discuss only European populations and, as said, shall not deal with exotic and alien races scattered among them nor with those quarters of the globe where the races of man are such that other physical characters must be called upon to provide clear definitions.
A fascinating subject would open up if we were to dwell upon the effect of racial combinations and disharmonies, as, for instance, where the mixed Nordic and Alpine populations of Lombardy usually retain the skull shape, hair color and stature of the Alpine race, with the light eye color of the Nordic race, or where the mountain populations along the east coast of the Adriatic from the Tyrol to Albania have the stature of the Nordic race and an Alpine skull and coloration.
III
RACE AND HABITAT
The laws which govern the distribution of the various races of man and their evolution through selection are substantially the same as those controlling the evolution and distribution of the larger mammals.
Man, however, with his superior mentality has freed himself from many of the conditions which impose restraint upon the expansion of animals. In his case selection through disease and social and economic competition has largely replaced selection through adjustment to the limitations of food supply.
Man is the most cosmopolitan of animals and in one form or another thrives in the tropics and in the arctics, at sea level and on high plateaux, in the desert and in the reeking forests of the equator. Nevertheless, the various races of Europe have each a certain natural habitat in which it achieves its highest development.
The Nordic Habitat
The Nordics appear in their present centre of distribution, the basin of the Baltic, at the close of the Paleolithic, as soon as the retreating glaciers left habitable land. This race was probably at that time in possession of its fundamental characters, and its extension from the plains of Russia to Scandinavia was not in the nature of a radical change of environment. The race in consequence is now, always has been and probably always will be, adjusted to certain environmental conditions, chief of which is protection from a tropical sun. The actinic rays of the sun at the same latitude are uniform in strength the world over and continuous sunlight affects adversely the delicate nervous organization of the Nordics. The fogs and long winter nights of the North serve as a protection from too much sun and from its too direct rays.
Scarcely less important is the presence of a large amount of moisture but above all a constant variety of temperature is needed. Sharp contrast between night and day temperature and between summer and winter are necessary to maintain the vigor of the Nordic race at a high pitch. Uniform weather, if long continued, lessens its energy. Too great extremes as in midwinter or midsummer in parts of New England are injurious. Limited but constant alternations of heat and cold, of moisture and dryness, of sun and clouds, of calm and cyclonic storms offer the ideal surroundings.
Where the environment is too soft and luxurious and no strife is required for survival, not only are weak strains and individuals allowed to survive and encouraged to breed but the strong types also grow fat mentally and physically, like overfed Indians on reservations or wingless birds on oceanic islands, which have lost the power of flight as a result of prolonged protective conditions.