Elizabeth Cary Agassiz, Louis Agassiz: his life and correspondence, third edition

[596] theory of the unity of mankind it is assumed that the different races have become what they are in consequence of their settlement in different parts of the world, and that the whole globe is everywhere a fit abode for human beings who adapt themselves to the conditions under which they live. According to the theory of a multiple origin of mankind the different races have first appeared in various parts of the globe, each with the peculiarities best suited to their primitive home. Aside from these theoretical views the fact is, that some races inhabit very extensive tracts of the earth's surface, and are now found upon separate continents, while others are very limited in their range. This distribution is such that there is no reason for supposing that the negro is less fitted permanently to occupy at least the warmer parts of North and South America, than is the white race to retain possession of their more temperate portions. Assuming our pure black race to be only two millions, it is yet larger than the whole number of several races that have held uninterrupted possession of different parts of the globe ever since they have been known to the white race. Thus the Hottentots and the Abyssinians have maintained themselves in