What, then, are the facts in the case of man? In producing crosses of distinct species, as in the case of the horse and ass, breeders are obliged to resort to expedients to overcome the natural repugnance to such intermixture. In the case of even the most extreme varieties of man, if such repugnance exists, it is voluntarily overcome, as the slave population of America testifies abundantly. By far the greater part of the intermixtures of races of men tend to increase of vital energy and vigor, as in the case of judicious crosses of some domestic animals. Where a different result occurs, we usually find sufficient secondary causes to account for it. I shall refer to but one such case—that of the half-breed American Indian. In so far as I have had opportunities of observation or inquiry, these people are prolific, much more so than the unmixed Indian. They are also energetic, and often highly intellectual; but they are of delicate constitution, especially liable to scrofulous diseases, and therefore not long-lived. Now this is precisely the result which often occurs in domestic animals, where a highly cultivated race is bred with one that is of ruder character and training; and it very probably results from the circumstance that the progeny may inherit too much of the delicacy of the one parent to endure the hardships congenial to the other; or, on the other hand, too much of the wild nature of the ruder parent to subsist under the more delicate nurture of the more cultivated. This difficulty does not apply to the intermixture of the Negro and the European, though between the pure races this is a cross too abrupt to be likely to be in the first instance successful.
6. The races of man may have originated in the same manner with the breeds of our domesticated animals. There are many facts which render it probable that they did originate in this way. Take color, for instance. The fair varieties of man occur only in the northern temperate zone, and chiefly in the equable climates of that zone. In extreme climates, even when cold, dusky and yellow colors appear. The black and blackish-brown colors are confined to the inter-tropical regions, and appear in such portions of all the great races of mankind as have been long domiciled there. Diet and degree of exposure have also evidently very much to do with form, stature, and color. The deer-eating Chippewayan of certain districts of North America is a better developed man than his compatriots who subsist principally on rabbits and such meaner fare; and excess of carbonaceous food, and deficiency of perspiration or of combustion in the lungs, appear everywhere to darken the skin. [173] The Negro type in its extreme form is peculiar to low and humid river valleys of tropical Africa. In Australasia similar characters appear in men of a very different race in similar circumstances. The Mongolian type reappears in South Africa. The Esquimau is like the Fuegian. The American Indian, both of South and North America, resembles the Mongol; but in several of the middle regions of the American continent men appear who approximate to the Malay. Everywhere and in all races coarse features and deviations from the oval form of skull are observed in rude populations. Where men have sunk into a child-like simplicity, the elongated forms prevail. Where they have become carnivorous, aggressive, and actively barbarous, the brachy-kephalic forms abound. These and many other considerations tend to the conclusion that these varieties are inseparably connected with external conditions. It may still be asked—Were not the races created as they are, with especial reference to these conditions? I answer no—because the differences are of a character in every respect like those that appear in other true species as the results of influences from without.
Farther, not only have we varieties of man resulting from the slow operation of climatal and other conditions, but we have the sudden development of races. One remarkable instance may illustrate my meaning. It is the hairy family of Siam, described by Mr. Crawford and Mr. Yule. [174] The peculiarities here consisted of a fine silky coat of hair covering the face and less thickly the whole body, with at the same time the entire absence of the canine and molar teeth. The person in whom these characters originated was sent to Ava as a curiosity when five years old. He married at twenty-two, his wife being an ordinary Burmese woman. One of two children who survived infancy had all the characters of the father. This was a girl; and on her marriage the same characters reappeared in one of two boys constituting her family when seen by Mr. Yule. Here was a variety of a most extreme character, originating without apparent cause, and capable of propagation for three generations, even when crossed with the ordinary type. Had it originated in circumstances favorable to the preservation of its purity, it might have produced a tribe or nation of hairy men, with no teeth except incisors. Such a tribe would, with some ethnologists, have constituted a new and very distinct species; and any one who had suggested the possibility of its having originated within a few generations as a variety would have been laughed at for his credulity. It is unnecessary to cite any further instances. I merely wish to insist on the necessity of a rigid comparison of the variations which appear in man, either suddenly or in a slow or secular manner, with the characters of the so-called races or species.
7. If we turn from the merely physical constitution of man, and inquire as to his psychical and spiritual endowments, it would be easy to show, as Dr. Carpenter and others have done, in opposition to Darwin, that on the one hand an impassable barrier separates man from the lower animals, and that on the other there is an essential unity among the races of men. But this subject I have discussed fully in the concluding chapters of my "Story of the Earth."
If man is thus so very variable, and if many of his leading varieties have existed for a very long time, does not the fact that we have but one species afford very strong evidence that species change only within fixed limits, and do not pass over into new specific types. Viewed in this way, variability within the specific limits becomes in itself one of the strongest arguments against the doctrine of descent with modification as a mode of origination of new species.
Let us now add to all this the farther consideration, so well illustrated in the "Reliquiæ Aquitanicæ" of Christy and Lartet, that the oldest-known men of the caves and gravels may be placed in one of the varieties, and this the most widely distributed, of modern man, and we have a further argument which tells most strongly against the assumption either of the extreme antiquity or of the unlimited variability of the human species.
FOOTNOTES
[1] Argyll's "Primeval Man."