L.--SPECIES AND VARIETAL FORMS WITH REFERENCE TO THE UNITY OF MAN.
In the concluding chapters of "Archaia" the nature of species, as distinguished from varieties, was discussed, and specially applied to the varieties and races of man. This discussion has been omitted from the text of the present work; but, in an abridged form, is introduced here, with especial reference to those more recent views of this subject now prevalent in consequence of the growth of the philosophy of evolution; but which I feel convinced must, with the progress of science, return nearer to the opinions held by me in 1860, and summarized below.
We can determine species only by the comparison of individuals. If all these agree in all their characters except those appertaining to s.e.x, age, and other conditions of the individual merely, we say that they belong to the same species. If all species were invariable to this extent, there could be no practical difficulty, except that of obtaining specimens for comparison. But in the case of very many species there are minor differences, not sufficient to establish specific diversity, but to suggest its possibility; and in such cases there is often great liability to error. In cases of this kind we have princ.i.p.ally two criteria: first, the nature and amount of the differences; secondly, their shading gradually into each other, or the contrary. Under the first of these we inquire--Are they no greater in amount than those which may be observed in individuals of the same parentage? Are they no greater than those which occur in other species of similar structure or habits? Do they occur in points known in other species to be readily variable, or in points that usually remain unchanged? Are none of them constant in the one supposed species, and constantly absent in the other? Under the second we ask--Are the individuals presenting these differences connected together by others showing a series of gradations uniting the extremes by minute degrees of difference? If we can answer these questions--or such of them as we have the means of answering--in the affirmative, we have no hesitation in referring all to the same species. If obliged to answer all or many in the negative, we must at least hesitate in the identification; and if the material is abundant, and the distinguishing characters clear and well defined, we conclude that there is a specific difference.
Species determined in this way must possess certain general properties in common:
1. Their individuals must fall within a certain range of uniform characters, wider or narrower in the case of different species.
2. The intervals between species must be distinctly marked, and not slurred over by intermediate gradations.
3. The specific characters must be invariably transmitted from generation to generation, so that they remain equally distinct in their limits if traced backward or forward in time, in so far as our observation may extend.
4. Within the limits of the species there is more or less liability to variation; and this, though perhaps developed by external circ.u.mstances, is really inherent in the species, and must necessarily form a part of its proper description.
5. There is also a physiological distinction between species, namely, that the individuals are sterile with one another, whereas this does not apply to varieties; and though Darwin has labored to break down this distinction by insisting on rare exceptional cases, and suggesting many supposed ways by which varieties of the same species might possibly attain to this kind of distinctness, the difference still remains as a fact in nature; though one not readily available in practically distinguishing species.
These general properties of species will, I think, be admitted by all naturalists as based on nature, and absolutely necessary to the existence of natural history as a science, independently of any hypotheses as to the possible changes of specific forms in the lapse of time. I now proceed to give a similar summary of the laws of the varieties which may exist--always be it observed, within the limits of the species.
1. The limits of variation are very different in different species.
There are many in which no well-marked variations have been observed.
There are others in which the variations are so marked that they have been divided, even by skilful naturalists, into distinct species or even genera. I do not here refer to differences of age and s.e.x. These in many animals are so great that nothing but actual knowledge of the relation that subsists would prevent the individuals from being entirely separated from one another. I refer merely to the varieties that exist in adults of the same s.e.x, including, however, those that depend on arrest of development, and thus make the adult of one variety resemble in some respects the young of another; as, for instance, in the hornless oxen, and beardless individuals among men.
If we inquire as to the causes on which the greater or less disposition to vary depends, we must, in the first place, confess our ignorance, by saying that it appears to be in a great measure const.i.tutional, or dependent on minute and as yet not distinctly appreciable structural, physiological, and psychical characters.
Darwin states that Pallas long ago suggested, from the known facts that the seeds of hybrid plants and grafted trees are very variable, the theory that mixture of breeds tends to produce variability; but Darwin does not seem to attach much importance to this, and admits our inability to explain the origin of these differences.[161] We know, however, certain properties of species that are always or usually connected with great liability to variation. The princ.i.p.al of these are the following: 1. The liability to vary is, in many cases, not merely a specific peculiarity; it is often general in the members of a genus or family. Thus the cats, as a family, are little p.r.o.ne to vary; the wolves and foxes very much so. 2. Species that are very widely distributed over the earth"s surface are usually very variable. In this case the capacity to vary probably adapts the creature to a great variety of circ.u.mstances, and so enables it to be widely distributed.
It must be observed here that hardiness and variability of const.i.tution are more important to extensive distribution than mere locomotive powers, for matters have evidently been so arranged in nature that, where the habitat is suitable, colonists will find their way to it, even in the face of difficulties almost insurmountable. 3.
Const.i.tutional liability to vary is sometimes connected with or dependent on extreme simplicity of structure, in other cases on a high degree of intelligence and consequent adaptation to various modes of subsistence. Those minute, simply organized, and very variable creatures, the Foraminifera, exemplify the first of these apparent causes; the crafty wolves furnish examples of the second. 4.
Susceptibility to variation is farther modified by the greater or less adaptability of the digestive and locomotive organs to varied kinds of food and habitat. The monkeys, intelligent, imitative, and active, are nevertheless very limited in range and variability, because they can comfortably subsist only in forests, and in the warmer regions of the earth. The hog, more sluggish and less intelligent, has an omnivorous appet.i.te, and no very special requirements of habitat, and so can vary greatly and extend over a large portion of the earth. Farther, in connection with this subject it may be observed that the conditions favorable to variation are also in the case of the higher animals favorable to domestication, while it may also be affirmed that, other things being equal, animals in a domesticated state are much more liable to vary than those in a wild state, and this independent of intentional selection. Darwin admits this, and gives many examples of it.
2. Varieties may originate in two different ways. In the case of wild animals it is generally supposed that they are gradually induced by the slow operation of external influences; but it is certain that in domesticated animals they often appear suddenly and unexpectedly, and are not on that account at all less permanent. A large proportion of our breeds of domestic animals appear to originate in this way. A very remarkable instance is that of the "Niata" cattle of the Banda Orientale, described by Darwin in his "Voyage of a Naturalist." These cattle are believed to have originated about a century ago among the Indians to the south of the La Plata, and the breed propagates itself with great constancy. "They appear," says Darwin, "externally to hold nearly the same relation to other cattle which bull-dogs hold to other dogs. Their forehead is very short and broad, with the nasal end turned up, and the upper lip much drawn back; their lower jaws project outward; when walking they carry their heads low on a short neck, and their hinder legs are rather longer compared with the front legs than is usual." It is farther remarkable in respect to this breed that it is, from its conformation of head, less adapted to the severe droughts of those regions than the ordinary cattle, and can not, therefore, be regarded as an adaptation to circ.u.mstances. In his later work on animals under domestication, Darwin gives many other instances of the origination of breeds of cattle and other animals in this abrupt and mysterious manner, and without any selection, though he strongly leans to the conclusion that slow and gradual changes are the most frequent causes of variation. It is to be observed, however, that very slow changes are in more danger of being accidentally diverted or obliterated by crossing, and that the first stages of an incipient change may be too unimportant to be permanent.
Many writers on the subject of the Unity of Man a.s.sume that any marked variety must require a long time for its production. Our experience in the case of the domestic animals teaches the reverse of this view; a very important point too often overlooked.
3. The duration or permanence of varieties is very different. Some return at once to the normal type when the causes of change are removed. Others perpetuate themselves nearly as invariably as species, and are named races. It is these races only that we are likely to mistake for true species, since here we have that permanent reproduction which is one of the characteristics of the species. The race, however, wants the other characteristics of species as above stated; and it differs essentially in having branched from a primitive species, and in not having an independent origin. It is quite evident that in the absence of historical evidence we must be very likely to err by supposing races to have really originated in distinct "primordial forms." Such error is especially likely to arise if we overlook the fact of the sudden origination of such races, and their great permanency if kept distinct. There are two facts which deserve especial notice, as removing some of the difficulty in such cases. One is that well-marked races usually originate only in domesticated animals, or in wild animals which, owing to accidental circ.u.mstances, are placed in abnormal circ.u.mstances. Another is, that there always remains a tendency to return, in favorable circ.u.mstances, to the original type. This tendency to reversion is much underrated by Darwin and his followers; yet they constantly recur to it as a means of proving possible derivation, and their writings abound in examples of it. Perhaps the most remarkable of these reversions are those which occur when varieties dest.i.tute of all the markings of the original stock are crossed and reproduce those markings, which Darwin shows to occur in pigeons and domestic fowls. The domesticated races usually require a certain amount of care to preserve them in a state of purity, both on this account and on account of the readiness with which they intermix with other varieties of the same species. Many very interesting facts in ill.u.s.tration of these points might be adduced. The domesticated hog differs in many important characters from the wild boar. In South America and the West Indies it has returned, in three centuries or less, to its original form.[162] The horse is probably not known in a state originally wild, but it has run wild in America and in Siberia. In the prairies of North America, according to Catlin[163] they still show great varieties of color. The same is the case in Sable Island, off the coast of Nova Scotia[164]
where herds of wild horses have existed since an early period in the settlement of America. In South America and Siberia they have a.s.sumed a uniform chestnut or bay color. In the plains of Western America they retain the dimensions and vigor of the better breeds of domesticated horses. In Sable Island they have already degenerated to the level of Highland ponies; but in all countries where they have run wild, the elongated and arched head, high shoulders, straight back, and other structural characters probably of the original wild horse, have appeared. We also learn from such instances that, while races among domesticated animals may appear suddenly, they revert to the original type, when unmixed, comparatively slowly; and this especially when the variation is in the nature of degeneracy.
4. Some characters are more subject to variation than others. In the higher animals variation takes place very readily in the color and texture of the skin and its appendages. This, from its direct relation to the external world, and ready sympathy with the condition of the digestive organs, might be expected to take the lead. In those domesticated animals which are little liable to vary in other respects, as the cat and duck, the color very readily changes. Next may be placed the stature and external proportions, and the form of such appendages as the external ear and tail. All these characters are very variable in domestic animals. Next we may place the form of the skull, which, though little variable in the wild state, is nearly always changed by domestication. Psychological functions, as the so-called instincts of animals, are also very liable to change, and to have these changes perpetuated in races. Very remarkable instances of this have been collected by Sir C. Lyell[165] and Dr. Prichard.
Lastly, important physiological characters, as the period of gestation, etc., and the structure of the internal organs connected with the functions of nutrition, respiration, etc., are little liable to change, and remain unaffected by the most extreme variations in other points; and it is, no doubt, in these more essential and internal parts that the tendency survives to return under favorable circ.u.mstances to the original type.
5. Varieties or races of the same species are fully reproductive with each other, which is not the case with true species. Mutual sterility of varieties of the same species is an exceptional peculiarity, if it ever truly exist; and, on the other hand, the cross-fertilization of varieties of the same species, whether in animals or plants, tends to vigorous life, and also to return to the primitive or average type. On the other hand, intermixture of distinct species rarely, if ever, occurs freely in nature. It is generally a result of artificial contrivance. Again, hybrids produced from species known to be distinct are either wholly barren, or barren _inter se_, reproducing only with one of the original stocks, and rapidly returning to it; or if ever fertile _inter se_, which is somewhat doubtful, rapidly run out. It has been maintained by Pallas and others, and Darwin leans to this idea, that there is still another possibility, namely, that of the perfect and continued fertility of such mixed races, especially after long domestication; but their proofs are derived princ.i.p.ally from the intermixture of the races of dogs and of poultry, which are cases actually in dispute at present, as to the original unity or diversity of the so-called species.
If we apply these considerations to man, our conclusion must be that, even in his bodily frame, he is not merely specifically but ordinally distinct from other animals, and that the differences between races of men are varietal rather than specific. This view is confirmed by the following facts:
1. The case of man is not that of a wild animal; and it presents many points of difference even from the case of the domesticated lower animals. According to the Bible history, man was originally fitted to subsist on fruits, to inhabit a temperate climate, and to be exempt from the necessity of destroying or contending with other animals.
This view unquestionably accords very well with his organization. He still subsists princ.i.p.ally on vegetable food, is most numerous in the warmer regions of the earth; and, when so subsisting in these regions, is naturally peaceful and timid. On the whole, however, his habits of life are artificial--more so than those of any domesticated animal. He is, therefore, in the conditions most favorable to variation. Again, man possesses more than merely animal instincts. His mental powers permit him to devise means of locomotion, of protection, of subsistence, far superior to those of any mere animal; and his dominant will, insatiable in its desires, bends the bodily frame to uses and exposes it to external influences more various than any inferior animal can dream of. Man is also more educable and plastic in his const.i.tution than other animals, owing both to his being less hemmed in by unchanging instincts, and to his physical frame being less restricted in its adaptations. If a single species, he is also more widely distributed than any other; and there are even single races which exceed in their extent of distribution nearly all the inferior animals. Nor is there anything in his structure specially to limit him to plains, or hills, or forests, or coasts, or inland regions. All the causes which we can suppose likely to produce variation thus meet in man, who is himself the producer of most of the distinct races that we observe in the lower animals. If, therefore, we condescend to compare man with these creatures, it must be under protest that what we learn from them must be understood with reference to his greater capabilities.
2. The races of men are deficient in some of the essential characters of species. It is true that they are reproduced with considerable permanency; though a great many cases of spontaneous change, of atavism, or return to the character of progenitors, and of slow variation under changed conditions, have been recorded. But the most manifest deficiency in true specific characters is in the invariable shading-off of one race into another, and in the entire failure of those who maintain the distinction of species in the attempt accurately to define their number and limits. The characters run into each other in such a manner that no natural arrangement based on the whole can apparently be arrived at; and when one particular ground is taken, as color, or shape of skull, the so-called species have still no distinct limits; and all the arrangements formed differ from each other, and from the deductions of philology and history. Thus, from the division of Virey into two species, on the entirely arbitrary ground of facial angle, to that of Bory de St. Vincent into fifteen, we have a great number and variety of distinctions, all incapable of zoological definition; or, if capable of definition, eminently unnatural. There are, in short, no missing links between the varieties of men corresponding to that which obtains between man and lower animals.
3. The races of men differ in those points in which the higher animals usually vary with the greatest facility. The physical characters chiefly relied on have been color, character of hair, and form of skull, together with diversities in stature and general proportion.
These are precisely the points in which our domestic races are most p.r.o.ne to vary. The manner in which these characters differ in the races of men may be aptly ill.u.s.trated by a few examples of the arrangements to which they lead.
Dr. Pickering, of the U. S. Exploring Expedition[166]--who does not, however, commit himself to any specific distinctions--has arranged the various races of men on the very simple and obvious ground of color.
He obtains in this way four races--the White, the Brown, the Blackish-brown, the Black. The distinction is easy; but it divides races historically, philologically, and structurally alike; and unites those which, on other grounds, would be separated. The white race includes the Hamite Abyssinian, the Semitic Arabian, the j.a.phetic Greek. The Ethiopian or Berber is separated from the cognate Abyssinian, and the dark Hindoo from the paler races speaking like him tongues allied to the Sanscrit. The Papuan, on the other hand, takes his place with the Hindoo; while the allied Australian must be content to rank with the Negro; and the Hottentot is promoted to a place beside the Malay. It is unnecessary to pursue any farther the arrangement of this painstaking and conscientious inquirer. It conclusively demonstrates that the color of the varieties of the human race must be arbitrary and accidental, and altogether independent of unity or diversity of origin.
Some use has been made, by the advocates of diversity of species, of the quality of the hair in the different races. That of the Negro is said to be flat in its cross section--in this respect approaching to wool; that of the European is oval; and that of the Mongolian and American round.[167] The subject has as yet been very imperfectly investigated; but its indications point to no greater variety than that which occurs in many domesticated animals--as, for instance, the hog and sheep. Nay, Dr. Carpenter states[168]--and the writer has satisfied himself of the fact by his own observation--that it does not exceed the differences in the hair from different parts of the body of the same individual. The human hair, like that of mammals in general, consists of three tissues: an outer cortical layer, marked by transverse striae, having in man the aspect of delicate lines, but in many other animals a.s.suming the character of distinct joints or prominent serrations; a layer of elongated, fibrous cells, to which the hair owes most of its tenacity; and an inner cylinder of rounded cells. In the proportionate development of these several parts, in the quant.i.ty of coloring matter present, and in the transverse section, the human hair differs very considerably in different parts of the body. It also differs very markedly in individuals of different complexions. Similar but not greater differences obtain in the hair of the scalp in different races; but the flatness of the Negro"s hair connects itself inseparably with the oval of the hair of the ordinary European, and this with the round observed in some other races. It generally holds that curled and frizzled hair is flatter than that which is lank and straight; but this is not constant, for I have found that the waved or frizzled hair of the New Hebrideans, intermediate apparently between the Polynesians and Papuans, is nearly circular in outline, and differs from European hair mainly in the greater development of the fibrous structure and the intensity of the color.
Large series of comparisons are required; but those already made point to variation rather than specific difference. Some facts also appear to indicate very marked differences as occurring in the same race from constant exposure or habitual covering; and also the occasional appearance of the most abnormal forms, without apparent cause, in individuals. The differences depending on greater or less abundance or vigor of growth of the hair are obviously altogether trivial, when compared with such examples as the hairless dogs of Chili and hairless cattle of Brazil, or even with the differences in this respect observed in individuals of the same race of men.
Confessedly the most important differences of the races of men are those of the skeleton, in all parts of which variations of proportion occur, and are of course more or less communicated to the muscular investments. Of these, as they exist in the pelvis, limbs, etc., I need say nothing; for, manifest though they are, they all fall far within the limits of variation in familiar domestic animals, and also of hereditary malformation or defect of development occurring in the European nations, and only requiring isolation for its perpetuation as a race. The differences in the skull merit more attention, for it is in this and in its enclosed brain that man most markedly differs from the lower animals, as well as race from race. It is in the form rather than in the mere dimensions of the skull that we should look for specific differences; and here, adopting the vertical method of Blumenbach as the most characteristic and valuable, we find a greater or less antero-posterior diameter--a greater or less development of the jaws and bones of the face. The skull of the normal European, or Caucasian of Cuvier, is round oval; and the jaws and cheek-bones project little beyond its anterior margin, when viewed from above. The skull of the Mongolian of Cuvier is nearly round, and the cheek-bones and jaws project much more strongly in front and at the sides. The Negro skull is lengthened from back to front; the jaws project strongly, or are prognathous; but the cheek-bones are little prominent. For the extremes of these varieties, Retzius proposed the names of brachy-kephalic or short-headed, and dolicho-kephalic or long-headed, which have come into general use. The differences indicated by these terms are of great interest, as distinctive marks of many of the unmixed races of men; but, when pushed to extremes, lead to very incorrect generalizations--as Professor D. Wilson has well shown in his paper on the supposed uniformity of type in the American races--a doctrine which he fully refutes by showing that within a very narrow geographical range this primitive and unmixed race presents very great differences of cranial form.[169] Exclusive of idiots, artificially compressed heads, and deformities, the differences between the brachy-kephalic and dolicho-kephalic heads range from equality in the parietal and longitudinal diameter to the proportion of about 14 to 24. As stated by some ethnologists, these differences appear quite characteristic and distinct; but, so soon as we attempt any minute discrimination, all confidence in them as specific characters disappears. In our ordinary European races similar differences, and nearly as extensive, occur. The dolicho-kephalic head is really only an immature form perpetuated; and appears not only in the Negro, but in the Esquimau, and in certain ancient and modern Celtic races. The brachy-kephalic head, in like manner, is characteristic of certain tribes and portions of tribes of Americans, but not of all; of many northern Asiatic nations; of certain Celtic and Scandinavian tribes; and often appears in the modern European races as an occasional character. Farther, as Retzius has well shown, the long heads and prominent jaws are not always a.s.sociated with each other; and his cla.s.sification is really the testimony of an able observer against the value of these characters. He shows that the Celtic and Germanic races (in part) have long heads and straight jaws; while the Negroes, Australians, Oceanians, Caribs, Greenlanders, etc., have long heads and prominent jaws. The Laplanders, Finns, Turks, Sclaves, Persians, etc., have short heads and straight jaws; while the Tartars, Mongolians, Incas, Malays, Papuans, etc., have short heads and prominent jaws.
Another defect in the argument often based on the diverse forms of heads is its want of acknowledgment of the ascertained and popularly known fact that these forms in different tribes or individuals of the same race are markedly influenced by culture and habits of life. In all races ignorance and debas.e.m.e.nt tend to induce a prognathous form, while culture tends to the elevation of the nasal bones, to an orthognathous condition of the jaws, and to an elevation and expansion of the cranium.[170]
Again, no adequate allowance has been made in the case of these forms of skull for the influence of modes of nurture in infancy. Dr. Morton, observing that the brachy-kephalic American skull was often unequal sided, and the occiput much flattened, suggests that this is "an exaggeration of the natural form produced by the pressure of the cradle-board in common use among the American natives." Dr. Wilson has noticed the same unsymmetrical character in brachy-kephalic skulls in British barrows, and has suspected some artificial agency in infancy; and says, in reference to the American instances, "I think it extremely probable that further investigation will tend to the conclusion that the vertical or flattened occiput, instead of being a typical characteristic, pertains entirely to the cla.s.s of artificial modifications of the natural cranium familiar to the American ethnologist."
While the points in which the races of men vary are those in which lower animals are most liable to undergo change, the several races display a remarkable constancy in those which are usually less variable. Prichard and Carpenter have well shown this in relation to physiological points, as, for instance, the age of arriving at maturity, the average and extreme duration of life, and the several periods connected with reproduction. The coincidence in these points alone is by many eminent physiologists justly regarded as sufficient evidence of the unity of the species.
4. It may also be affirmed, in relation to the varieties of man, that they do not exceed in amount or extent those observed in the lower animals. If with Frederick Cuvier, Dr. Carpenter, and many other naturalists, we regard the dog as a single species, descended in all probability from the wolf, we can have no hesitation in concluding that this animal far exceeds man in variability.[171] But this is denied by many, not without some show of reason; and we may, therefore, select some animal respecting which little doubt can be entertained. Perhaps the best example is the common hog (_Sus scrofa_), an undoubted descendant of the wild boar, and a creature especially suitable for comparison with man, inasmuch as its possible range of food is very much the same with his, which is not the case with any other of our domesticated animals; and as its headquarters as a species are in the same regions which have supported the greatest and oldest known communities of men. We may exclude from our comparison the Chinese hog, by some regarded as a distinct species (_Sus Indicus_), though no wild original is known, and it breeds freely with the common hog. The color of the domestic hog varies, like that of man, from white to black; and in the black hog the skin as well as the hair partakes of the dark color. The abundance and quality of the hair vary extremely; the stature and form are equally variable, much more so than in man. Blumenbach long ago remarked that the difference between the skull of the ordinary domestic hog and that of the wild boar is quite equal to that observed between the Negro and European skulls. Darwin shows that it is much greater, and ill.u.s.trates this by an amusing pair of portraits. The breeds of swine even differ in directions altogether unparalleled in man. For instance, both in America and Europe solid-hoofed swine have originated and become a permanent variety; and there is said to be another variety with five toes.[172] These are the more remarkable, because, in the American instances, there can be no doubt that it is the common hog which has a.s.sumed these abnormal forms.
5. All varieties or races of men intermix freely, in a manner which strongly indicates specific unity. We hold here, as already stated, that no good case of a permanent race arising from intermixture of distinct species of the lower animals has been adduced; but there is another fact in relation to this subject which the advocates of specific diversity would do well to study. Even in varieties of those domestic animals which are certainly specifically identical, as the hog, the sheep, the ox--although crosses between the varieties may easily be produced--they are not readily maintained, and sometimes tend to die out. What are called good crosses lead to improved energy, and continual breeding in and in of the same variety leads to degeneracy and decay; but, on the other hand, crosses of certain varieties are proved by experience to be of weakly and unproductive quality; and every practical book on cattle contains remarks on the difficulty of keeping up crosses without intermixture with one of the pure breeds. It would thus appear that very unlike varieties of the same species display in this respect, in an imperfect manner, the peculiarities of distinct species. It is on this principle that I would in part account for some of the exceptional facts which occur in mixed races of men.
What, then, are the facts in the case of man? In producing crosses of distinct species, as in the case of the horse and a.s.s, 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 const.i.tution, 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 circ.u.mstance 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 princ.i.p.ally 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 circ.u.mstances. 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 coa.r.s.e 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 ill.u.s.trate 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 const.i.tuting 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 circ.u.mstances 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 const.i.tuted 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 const.i.tution 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 impa.s.sable 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 pa.s.s 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 ill.u.s.trated in the "Reliquiae Aquitanicae" 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 a.s.sumption either of the extreme antiquity or of the unlimited variability of the human species.
FOOTNOTES
[Footnote 1: Argyll"s "Primeval Man."]
[Footnote 2: Essays on Theism, 1875.]
[Footnote 3: John i., 9.]
[Footnote 4: Hebrews xi., 3.]
[Footnote 5: I avail myself of the condensed translation in Bancroft"s "Native Races," vol. iii. The original French translation of Bra.s.seur du Bourbourg is more full.]