Unfortunately, modern science has as yet found no clue to this maze of opinions. No admissible theory has been advanced which affords the least light upon the subject, and, in all probability, the various types differ as much from their common progenitor--if they possess one--as they do among themselves. The causes of these deviations are exceedingly difficult to ascertain. The believers in the unity of origin pretend to find them, as I remarked before, in various local circumstances, such as climate, habits, &c. It is impossible to coincide with such an opinion, for, although these circumstances have always existed, they have not, within historical times, produced such alterations in the races which were exposed to their influence as to make it even probable that they were the causes of so vast and radical a dissimilarity as we now see before us. Suppose two tribes, not yet departed from the primitive type, to inhabit, one an alpine region in the interior of a continent, the other some isolated isle in the immensity of the ocean. Their atmospheric and alimentary conditions would, of course, be totally different. If we further suppose one of these tribes to be abundantly provided with nourishment, and the other possessing but precarious means of subsistence; one to inhabit a cold latitude, and the other to be exposed to the action of a tropical sun; it seems to me that we have accumulated the most essential local contrasts. Allowing these physical causes to operate a sufficient lapse of time, the two groups would, no doubt, ultimately assume certain peculiar characteristics, by which they might be distinguished from each other. But no imaginable length of time could bring about any essential, organic change of conformation; and as a proof of this assertion, I would point to the populations of opposite portions of the globe, living under physical conditions the most widely different, who, nevertheless, present a perfect resemblance of type. The Hottentots so strongly resemble the inhabitants of the Celestial Empire, that it has even been supposed, though without good reasons, that they were originally a Chinese colony. A great similarity exists between the ancient Etruscans, whose portraits have come down to us, and the Araucanians of South America. The features and outlines of the Cherokees seem to be perfectly identical with those of several Italian populations, the Calabrians, for instance. The inhabitants of Auvergne, especially the female portion, much more nearly resemble in physiognomy several Indian tribes of North America than any European nation. Thus we see that in very different climes, and under conditions of life so very dissimilar, nature can reproduce the same forms. The peculiar characteristics which now distinguish the different types cannot, therefore, be the effects of local circumstances such as now exist.[143]