CHAPTER XIII

THE LAW OF SIMILARITY

A powerful instinct keeps animals from pairing with individuals belonging to another species than their own. “L’animal,” says M. Duvernoy, “a l’instinct de se rapprocher de son espèce et de s’éloigner des autres, comme il a celui de choisir ses aliments et d’éviter les poisons.”[1629] Among Birds, there are found a small number of wild hybrids, nearly all of which are in the order of Gallinae, and most of which belong to the genus Tetrao.[1630] But among Insects, Fishes, and Mammals, living in a state of nature, hybridism is unknown or almost so.[1631] And, even among domesticated mammals, some tricks are often required to deceive the male, and so to conquer its aversion to a female of a different species. The stallion, for instance, who is to cover a she-ass, is frequently first excited by the presence of a mare, for which, at the proper moment, the she-ass is substituted.[1632]

We may be sure that, were it not for this instinctive feeling, many more animal hybrids would be naturally produced than is the case. In the vegetable kingdom, where the play of instincts is altogether out of the question, bastards occur much more frequently;[1633] and in captivity a considerable number of animal hybrid forms are produced that are never met with in a state of nature.[1634] Yet, according to Mr. Darwin, there are good grounds for the doctrine of Pallas, that the conditions to which domesticated animals and cultivated plants have been subjected, generally eliminate the tendency towards mutual sterility, so that the domesticated descendants of species which in their natural state would have been in some degree sterile when crossed, become perfectly fertile.[1635]

The origin of this instinct, which helps to keep even closely allied species in a state of nature distinct, seems to be sufficiently clear. The number of species which have proved fertile together are very limited, and the fertility of the hybrid offspring is almost constantly diminished, often even to a very great extent. Of course, no one now talks of the sterility of hybrids as a moral necessity—hybrids being _animalia adulterina_,—or as the result of a special divine decree, that new species should not be multiplied indefinitely.[1636] M. Isidore Geoffroy has shown not only that hybrids may be fertile, but that “infertile” hybrids are, properly speaking, merely the hybrids which are most rarely fertile, their sterility never being absolute.[1637] Moreover, as has been pointed out by Mr. Wallace, in almost all the experiments that have hitherto been made in crossing distinct species, no care has been taken to avoid close interbreeding; hence these experiments cannot be held to prove that hybrids are in all cases infertile _inter se_.[1638] But looking to all the ascertained facts on the intercrossing of plants and animals, we may with Mr. Darwin conclude that some degree of sterility in hybrids is an extremely general result.[1639] This being the case with the hybrids of our domesticated animals, it must be so all the more with animals in a state of nature, which generally live under conditions less favourable to mutual fertility. It is easy to understand, then, that instincts leading to intercrossing of different species, even if appearing occasionally, never could be long-lived, as only those animals which preferred pairing with individuals of their own species, gave birth to an offspring endowed with a normal power of reproduction, and thus became the founders of numerous generations that inherited their instincts.

The relative or absolute sterility characterizing first crosses and hybrids depends upon a biological law which might be called the “Law of Similarity.” The degree of sterility, in either case,[1640] runs, at least to a certain extent, parallel with the general affinity of the forms that are united. Thus, most animal hybrids are produced by individuals belonging to the same genus, whilst species belonging to distinct genera can rarely, and those belonging to distinct families perhaps never, be crossed.[1641] The parallelism, however, is not complete, for a multitude of closely allied species will not unite, or unite only with great difficulty, though other species, widely different from each other, can be crossed with facility. Hence Mr. Darwin infers that the difficulty or facility in crossing “apparently depends exclusively on the sexual constitution of the species which are crossed, or on their sexual elective affinity, _i.e._, the ‘Wahlverwandtschaft’ of Gärtner.” But as species rarely, or never, become modified in one character, without being at the same time modified in many, and as systematic affinity includes all visible resemblances and dissimilarities, any difference in sexual constitution between two species would naturally stand in more or less close relation with their systematic position.[1642]

With regard to the instinct in question, man follows the general rule in the animal kingdom. Our notions of morality are closely connected with the instinctive feelings engraved in our nature; and bestiality is commonly looked upon as one of the most heinous crimes of which man can make himself guilty. Several passages both in ancient[1643] and modern writers[1644] prove the occasional occurrence of this crime, but always under circumstances analogous to those under which single birds sometimes form connections against nature,[1645] _i.e._, either because of isolation, or on account of vitiated instincts.[1646]

* * * * *

Supporters of the hypothesis that the several races of man are distinct species of the genus Homo, assert that an instinctive aversion similar to that which keeps different animal species from intermingling, exists also between the various human races.[1647] It may be noted by the way that, even if this were true, the idea that mankind consists of various species might be controverted; for certain races of domestic or semi-domesticated animals seem to prefer breeding with their own kind and refuse to mingle with others. Thus Mr. Bennett states that the dark and pale coloured herds of fallow deer, which have long been kept together in the Forest of Dean and two other places, have never been known to mingle. On one of the Faroe Islands, the half-wild native black sheep are said not to have readily mixed with the imported white sheep. And in Circassia, where six sub-races of the horse are known and have received distinct names, horses of three of these races, whilst living a free life, almost always refuse to mingle and cross, and will even attack each other.[1648] As for man, there are many races who dislike marrying persons of another race, but the motives are various. The different ideas of beauty no doubt play an important part. Mr. Winwoode Reade does not think it probable that negroes would prefer even the most beautiful European woman, on the mere grounds of physical admiration, to a good-looking negress.[1649] A civilized race does not readily intermingle with one less advanced in civilization, from the same motives as those which prevent a lord from marrying a peasant girl. And more than anything else, I think, the enmity, or at least, want of sympathy, due to difference of interests, ideas, and habits, which so often exist between distinct peoples or tribes, helps to keep races separate. But such reasons as these have nothing in common with the instinctive feeling which deters animals of distinct species from pairing with each other. Hence, when two races come into very close mutual contact, especially if they are at about the same stage of civilization, their dislike to intermarriage commonly disappears.

Mongrels form, indeed, a large proportion of the inhabitants of the world. It is doubtful whether there are any pure races in Europe; not even the Basques can pretend to purity of blood.[1650] M. Broca found, when investigating the subject of stature, that nineteen-twentieths of the whole population of France presented, in various degrees, the characters of mixed races.[1651] In North America, different races intermingle more and more every day. In Greenland, according to Dr. Nansen, in the course of a century and a half there has been such an intermixture of races that it would now be extremely difficult, if not impossible, to find a true Eskimo throughout the whole of the west coast; and the Europeans, far from being disliked by the native women have succeeded in inspiring them with so much respect that the “simplest European sailor is preferred to the best Eskimo seal catcher.”[1652] In Mexico, the Spanish mixed breeds constitute two-thirds or three-fourths of the whole population;[1653] and South America, to quote a French writer, is “le grand laboratoire des nations hybrides ou métisses modernes.”[1654] Of twelve millions of mongrels, which is the estimated number of mongrels on the face of the globe, no fewer than eleven millions are found there.[1655] Even in remote Tierra del Fuego, according to Mr. Bridges, some mongrels of European fathers and indigenous mothers have appeared during the last few years.

In Asia there are numberless instances of intermixture of breed between the Tartars, Mongols, and Tunguses, and the Russians and Chinese, &c.[1656] In India there are many Eurasians; in the Indian Archipelago Chinese and Malays intermarry;[1657] and, in the Islands of the South Sea, the mongrels of European fathers amount to a considerable number. In Africa, the eastern Soudan is a great centre of mixed breeds between races much removed from one another. And, in Southern Africa, the Griquas—the offspring of Dutch colonists and Hottentot women—form a very distinct race.

As far as we know, there are no human races who, when intermingled, are entirely sterile. But as regards the degree of fertility of first crosses and of mongrels, the opinions of different anthropologists vary considerably. Those who do not believe in the unity of the human race have been especially solicitous to prove that crosses are almost inevitably followed by bad results in that respect. Thus Dr. Knox thinks that the half-breeds, if they were abandoned to themselves and no longer had access to pure races, would rapidly disappear, the “hybrid” being rejected by nature as a degradation of humanity.[1658] Dr. Nott asserts that, when two proximate species of mankind, two races bearing a general resemblance to each other in type, are bred together, they produce offspring perfectly prolific; but that, when species the most widely separated, such as the Anglo-Saxon and the negro, are crossed, the mulatto offspring are but partially prolific, and acquire an inherent tendency to run out, and become eventually extinct, when kept apart from the parent stocks.[1659] The same opinion is entertained by M. Broca, and by M. Pouchet, who thinks that the crossed race will exist only if it continues to be supported by the two creating types remaining in the midst of it.[1660]

On the other hand, Dr. Prichard believes it may be asserted, without the least chance of valid contradiction, that mankind, of all races and varieties, are equally capable of having offspring by intermarriage, and that such connections are equally prolific whether contracted between individuals of the same variety or of the most dissimilar varieties. “If there is any difference,” he says, “it is probably in favour of the latter.”[1661] According to M. Godron, the mongrels have generally shown a higher degree of fertility than their parent races;[1662] and M. Quatrefages asserts that mulattoes are as fruitful as pure breeds.[1663]

It is to be regretted that so little attention has for some time been paid to this most important question. The result is that the effects of the intermixture of races are not much better known now, than they were twenty or thirty years ago. The only thing which may be considered certain is, that the hypothesis of the depressing influence of crossing upon fertility, as the theory has generally been propounded, involves a great deal of exaggeration. It is chiefly owing to M. Broca’s celebrated essay, ‘Sur l’hybridité,’ that this doctrine has been so widely accepted. He asserts that the connections of Europeans with Australian women have proved very slightly prolific, and that the mongrels resulting from them are almost sterile. “No statistical writer,” he says, “nor any historian, enumerates cross-breeds among the Australian population.”[1664] Yet, this land has for a considerable time been inhabited by European colonists, many of whom have not had opportunities of marrying wives of their own race. It has also been shown that the cohabitation of whites and native women is very common in Australia. But the number of mongrels there is, nevertheless, exceedingly small, so small that in the native dialects there does not exist a single word to designate them.[1665]

Supposing that these remarkable statements referred chiefly to the eastern and southern parts of the Australian continent, I asked Bishop R. Salvado and the Rev. Joseph Johnston, living in West Australia, to inform me whether, in that country, any mixed race exists, and, if so, whether it is fruitful or not. From the former, who has lived among the West Australian aborigines for more than forty years, and through an excellent work on their life and customs has gained the reputation of a first-rate authority, I had the pleasure of receiving the following answer, dated New Norcia, October 17, 1888:—“With regard to the sterility of the half-caste natives, of which I had no experience when I wrote my book, I am able now to deny it altogether, except in cases similar to those among the Europeans. I know several cases of husband and wife, half-caste natives, having at present six and seven and even eight children, and they may in time have more; and I know a good many Europeans who, having married native women, have several children. In fact, in the case of one of those marriages there were six children, and in another seven, and I could give the name of each of them.” The Rev. J. Johnston writes, “There is a school for half-caste boys and girls at Perth, and they seem bright and intelligent children, not unlike Polynesian children. As they grow up, they go out to service, and some of the youths are employed as post and telegraph messengers.... At the New Norcia mission, there are several half-caste families, as well as blacks, and they all have children.” The following statement of Mr. Taplin referring to the aborigines of the Lower Murray, goes in the same direction:—“The pure blacks,” he says, “are not so healthy as the half-castes. Always the children of two half-castes will be healthier and stronger than either the children of blacks or the children of a black and a half-caste. When a half-caste man and woman marry, they generally have a large and vigorous family. I could point to half a dozen such.”[1666]

These statements of highly competent persons are, I think, quite sufficient to disprove M. Broca’s hypothesis. They show that, if a mixed race is almost wanting in certain parts of Australia, this does not depend upon physiological conditions of the kind suggested. It should be remembered that the sexual intercourse of Europeans with savage women is most commonly transitory and accidental, and frequently takes place with prostitutes or licentious women, who are generally known to be sterile. And, even when the white settler takes a native’s daughter to live with him under his own roof as a wife or a concubine, and accustoms her to a half-civilized manner of living, her unfruitfulness[1667] may be owing to quite another cause than the mixture of blood. Mr. Darwin has shown that changed conditions of life have an especial power of acting injuriously on the reproductive system. Thus animals, as also plants, when removed from their natural conditions, are often rendered in some degree infertile or completely barren, even when the conditions have not been greatly changed. And this failure of animals to breed under confinement cannot, at least to any considerable extent, depend upon a failure in their sexual instincts. “Numerous cases,” says Mr. Darwin, “have been given of various animals which couple freely under confinement, but never conceive; or, if they conceive and produce young, these are fewer in number than is natural to the species.”[1668] It is reasonable to suppose that savage man, when he moves into more civilized conditions, is subject to the same law. Indeed, statements have been reported to me, which tend to show that the indigenous women at the Polynesian missionary stations have become less fruitful than they were in their native state. As to the alleged sterility of crosses between the European and Australian races, it should be observed that the rarity of mongrels in certain parts of Australia is more or less owing to the natives themselves habitually destroying the half-castes.[1669] The Rev. A. Meyer states that, in the Encounter Bay tribe, “nearly all the children of European fathers used to be put to death;”[1670] whilst, among the Narrinyeri, about one-half of the half-caste infants fell victims to the jealousy of their mothers’ husbands.[1671] But with regard to the West Australian aborigines in the neighbourhood of Fremantle, the Rev. J. Johnston writes that he does not think it has been the custom there to destroy the half-caste illegitimate offspring of black women, as he never heard of such a thing,—a fact which may account for the comparatively large number of mongrels in that part of the continent.

Other statements also, adduced as evidence for the hypothesis of M. Broca, have proved more or less untrustworthy. Thus the alleged sterility of the mulattoes of Jamaica[1672] has been disputed by other writers.[1673] So also v. Görtz’s statement that the children of the Dutch and Malay women in Java (Lipplapps) are only productive to the third generation,[1674] has been called in question.[1675]

Yet, although we may consider it certain that the diversities even between the races which least resemble each other are not so great but that, under favourable conditions, a mixed race may easily be produced, I do not deny the possibility of crossing being, to a certain extent, unfavourable to fertility. The statements as to the rapid increase of some mixed races do not prove the reverse. For the bad result of crossing would not necessarily appear at once; and a drop of pure blood would be sufficient to increase fertility, just as, when a hybrid is crossed with either pure parent species, sterility is usually much lessened.[1676] It is a remarkable fact that mixed marriages between Jews and persons of other races are comparatively infertile. In Prussia, these marriages have been separately registered since 1875, and between that year and 1881 there was an average of 1·63 to a marriage, whereas, during the same period, pure Jewish marriages resulted in an average of 4·41 children or very nearly three times as many. In Bavaria, between 1876 and 1880, the numbers were only 1·1 per marriage against 4·7 children to purely Jewish marriages. And this conspicuous infertility implies greater sterility. Among fifty-six such marriages, with regard to which Mr. Jacobs ascertained the results, no fewer than nine were sterile, _i.e._, 18 per cent.,—a striking contrast to the number of sterile marriages which he found in seventy-one marriages between Jewish cousins, where the percentage of sterility was only 5·4 per cent.[1677] Mr. Jacobs, however, informs me that it has been suggested that this infertility may be due rather to the higher age at which such marriages are likely to take place. There is still a strong feeling against them among Jews, which is only likely to be overcome after independence of thought and position has been reached. At the same time Mr. Jacobs does not consider this sufficient to account for the very great discrepancy. But we must not, of course, take for granted that the crossing of any two races has the same effects as the crossing of Jewish and non-Jewish Europeans seems to have.

Even if it could be proved, however, that mixture of races produces lessened fertility of first crosses and of mongrels, this would not make it necessary for us to reject the doctrine of the unity of mankind. It is true that the domesticated varieties both of animals and of plants, when crossed, are as a general rule prolific, in some cases even more so than the purely bred parent varieties; whereas species, when crossed, and their hybrid offspring, are almost invariably in some degree sterile. But this rule is not altogether without exceptions. Even Agassiz condemned the employment of fertility of union as a limiting principle. He considered this a fallacy, “or at least a _petitio principii_, not admissible in a philosophical discussion of what truly constitutes the characteristics of species.”[1678] Thus the red and yellow varieties of maize are in some degree infertile when crossed, and the blue-and the red-flowered forms of the pimpernel, considered by most botanists to be the same species, as they present no differences of form or structure, are, according to Gärtner, mutually sterile. Moreover, Mr. Darwin’s investigations on dimorphic and trimorphic plants have shown that the physiological test of lessened fertility, both in first crosses and in hybrids, is no safe criterion of specific distinction.[1679] As for animals, Professor Vogt asserts that, in the opinion of experienced breeders, certain races can with difficulty be made to pair, and the fertility of the mongrels soon diminishes, whilst other races pair readily and are prolific.[1680] Sir J. Sebright says, “Although I believe the occasional intermixture of different families to be necessary, I do not, by any means, approve of mixing two distinct breeds, with the view of uniting the valuable properties of both: this experiment has been frequently tried by others as well as by myself, but has, I believe, never succeeded. The first cross frequently produces a tolerable animal, but it is a breed that cannot be continued.”[1681]