These facts, to which many more might be added, should be sufficient to convince every philosophic naturalist, who duly estimates what is required for the establishment of spe cific distinctions, that none such can be laid down among the different races of mankind, upon the foundation of cranial conformation alone. Those ethnologists who hold the doctrine of originally distinct stocks, which (they maintain) have continued to preserve their characteristic features through succes sive generations, have been obliged to admit, not three or five varieties of cranial conform ation, but twenty or thirty ; and as we in crease our acquaintance with the physical characters of tribes at present little known. the number requires continual enlargement. And whether the types selected be few or many, they are always found to be con nected by such a gradation of intermediate or transitional forms, that the well-marked boundary-lines which are necessary for the limitation of species, cannot be drawn with the slightest show of justification. It is not meant to be here asserted, that the absence of any such definite peculiarities of cranial con formation is of itself a sufficient reason for regarding the several races of mankind as specifically identical. On the contrary, as we have already seen, the genus Felis contains species as unmistakeably distinct as the lion and the tiger, between which there is no appreciable difference in cranial conformation Ail that we have a right to affirm is (I.), that the most extreme differences in the configura tion of the skull, existing among the several races of men, are not greater than those which present themselves among races of domesti cated mammals known to have had a common origin (e. g. those of the hog), and are not nearly so great as those existing among other races of mammals (as the various breeds of dog,) which are generally believed to have had a common origin; and (2.) that, as in the case of the domesticated races, the distinctive characters are by no means clearly marked out, but that those of the typical forms are softened down in intermediate gradations, so as to present a continuous series from one type to another, in which no such hiatus is left, as would justf& the assumption of the specific distinctness of those types. This last fact of itself invalidates that supposition of the uniform transmission of physical cha racters from parent to offspring, on which the presumption of original distinctness mainly rests. For, on the theory of specific distinct ness, all the descendants of the same parentage should repeat the characters of their ances tors without essential modification ; whereas we find, as a matter of fact, that the distinc tive characters are perpetuated in their full intensity in only a small proportion of each race, and that in the great masses they are so shaded off as gradually to disappear. And this must be admitted, whatever types we may select as those representing the original species ; unless we go to the extreme length of selecting a distinct type for every distin guishable modification in the conformation of the skull, which would be a sort of reductio ad absurdunz of the hypothesis.
We are thus led to the second branch of the inquiry, namely, whether there is ade quate evidence that the cranial characters of the several races are really thus transmitted, with little or no modification, from generation to generation, or whether an actual passage may be effected in time from one type to another. Now, every one who has been accustomed to discriminate the varieties of cranial conformation which present them selves within his own range of observation, must have noticed that not only between the parents and their offspring, but also among the different children of the same parentage, a considerable diversity not unfrequently exists. Further, on looking at the various individuals composing the ramifications of a particular family, it is frequently observable that they agree among themselves in some peculiarity of cranial configuration, which seems (from the evidence of portraits, busts, &c.) to have been transmitted downwards
for centuries; and by this very character it may be separated from other families, which are in like manner distinguished for their re spective peculiarities. Now, there can be no reasonable doubt that many such families had originally a common ancestry, so that there must have been a time when each of these peculiarities first manifested itself in its own branch of the common stock ; for, if this be not admitted, we must suppose each of them to have descended from a distinct pair of " protoplasts." It is obvious, then, that the question of possible modification is only one of degree ; and judging by the analogy of the domesticated races, by the amount of varia tion exhibited under circumstances not very dissimilar, and by the considerations already advanced (p.1303. et seq.) respecting the pro bable sources of such variations, we should be prepared to expect that even the widest diver sities which have been described, might have been occasioned by the sufficiently-prolonged influence of external causes acting upon a succession of generations. That such has been the case to a considerable extent, would appear in some instances from the direct evi dence of history ; in other instances it would seem a necessary inference from the facts of philology; whilst in others, again, the two classes of evidentiary facts, neither of them sufficient in themselves, tend to confirm each other.
One of the most striking examples of this kind is afforded by the change in cranial conformation from the pyramidal to the ellip tical, as well as in other characters, especially the length and abundance of the beard, which has taken place among the Turks of Europe and Western Asia. These so closely accord in physical characters with the great bulk of European nations, and depart so widely from the Turks of Central Asia, that many writers have referred the former to the (so-called) Caucasian, rather than to the Mongolian stock. Yet historical and philo logical evidence sufficiently proves, that the Western Turks originally belonged to the Central Asiatic group of with which the eastern portion of their nation still re mains associated, not only in its geographical position, but in its language, physical charac ters, and habits of life ; and that it is in the western branch, not in the eastern, that the change has taken place. Some writers have supposed that this change might he explained as the result of an intermixture of the Turkish race with the inhabitants of the countries they have conquered, or by the introduction of Georgian or Circassian slaves into their harems. But the cause suggested is plainly inadequate to the effect. For we know that in the Christian countries subjugated by the Turks, the conquering and the conquered races have been kept from properly domestic intermixture by mutual hatred, fostered by their difference in religion and manners ; and although Greek, Georgian, and Circassian females have been introduced into the harems of those who could afford to purchase them, yet any other modification which has been effected by their means must have had but an insignificant effect upon the mass of the population, since the pure Turkish descent of the poorer classes must have been but little interrupted, and universal experience shows that if the " cross-breeding" be not kept up, any new element introduced into a race speedily disappears. Even admitting that some modification may have been thus engen dered, we cannot fairly attribute to it more than a very trifling share in the result ; since the effect of intermixture would simply have been to produce a hybrid or intermediate race, instead of the entire substitution of the elliptical type, which now manifests itself among the comparatively civilised Western Turks, whilst those which inhabit Central Asia, and retain the nomadic habits of their ancestors, have retained also their cranial conformation.