Whether the “Caucasian” race is to be divided into two or three main subdivisions depends upon the classificatory value to be attached to certain differences in the skeleton and particularly to the shape of the skull. The student in his further reading will meet with constant references to round-skulled (Brachycephalic) and long-skulled peoples (Dolichocephalic). No skull looked at from above is completely round, but some skulls (the dolichocephalic) are much more oblong than others; when the width of a skull is four-fifths or more of its length from back to front, that skull is called brachycephalic; when the width is less than four-fifths of the length, the skull is dolichocephalic. While some ethnologists regard the difference between brachycephaly and dolichocephaly as a difference of quite primary importance, another school—which the writer must confess has entirely captured his convictions—dismisses this as a mere secondary distinction. It seems probable that the skull shapes of a people may under special circumstances vary in comparatively few generations.[73]
We do not know what influences alter the shape of the skull, just as we do not know why people of British descent in the Darling region of Australia (“Cornstalks”) grow exceptionally tall, or why in New England their jaw-bones seem to become slighter and their teeth in consequence rather crowded. Even in Neolithic times dolichocephalic and brachycephalic skulls are found in the same group of remains and often buried together, and that is true of most peoples to-day. Some peoples, such as the mountain people of central Europe, have more brachycephalic individuals per cent. than others; some, as the Scandinavians, are more prevalently dolichocephalic. In Neolithic Britain and in Scandinavia the earliest barrows (= tomb mounds) are long grave-shaped barrows and the late ones round, and the skulls found in the former are usually dolichocephalic and in the latter most frequently brachycephalic. This points perhaps to a succession of races in western Europe in the Neolithic Period (see Chapter XLV), but it may also point to changes of diet, habit, or climate.