730 THE AMERICAN JOURNAL OF SOCIOLOGY
of the skin and texture of the hair would seem to negative the possibility of a common origin. But a careful study of all the intermediate conditions shows that there are gradations between all such characters. These differences can all be accounted for by long exposure to different climatic conditions, by personal pref- erences and sexual selections arising therefrom, and by many other influences which are observed to act upon the physiological and biological elements entering into the problem. The one fundamental fact that all races, regardless of color, size, form, or any other differences, are perfectly fertile inter se, proves con- clusively that the races of men all belong to one animal species, and this, under modern conceptions of the meaning of species, implies common descent and genetic filiation. It is inconceivable that two animal forms should, under the spontaneous formative influences of nature, be molded by the " fortuitous con- course of atoms " into such a condition of external and internal identity that when they should chance to meet through an equally fortuitous conjuncture they would recognize each other as belonging to a common " kind," and, uniting according to the laws of nature, would be able to originate a new race of beings. The mathematical law of probabilities, as well as the observed course of natural events, in every department of knowledge dis- tinctly negatives such a violent assumption and supports the teachings of biology that man is everywhere the same.
But, as has already been remarked, the period of ethnic and social differentiation has now long passed, and that of ethnic and social integration has begun. Indeed, this latter process has been long going on. We are not sufficiently acquainted with any but the white races to be able to describe its effects, but they have doubtless been as marked in the yellow and even in the black races as in the white races. Here it has gone on through a long series of social assimilations until it has evolved a number of great amalgamated nationalities, such as the French, German, Italian, Spanish, Russian, and English peoples, all of which, though demonstrably composed of a great number of heterogeneous racial elements, are now compactly integrated into what may still be called distinct races. For under this view
