Polygenism

“ Nearly all the polygenistic arguments are included in the following:—“The difference between the Negro and the White is too great for them to belong to the same species.” These types are the two extremes in the human series. Therefore, if it can be shown that between the two extremes, the limits of variation are almost always greater in plants and animals than in man, we shall have undermined the foundation of the whole polygenistic doctrine. ”

“ We have now established the bases for a practicable eugenics program. Men differ; these differences are inherited; therefore the make-up of the race can be changed by any method which will alter the relative proportions of the contributions which different classes of men make to the following generation.
For applied eugenics, it is sufficient to know that mental and physical differences are inherited; the exact manner of inheritance it would be important to know, but even without a knowledge of the details of the mechanism of heredity, a program of eugenics is yet wholly feasible. ”

“ Finally, we may conclude that when the principle of evolution is generally accepted, as it surely will be before long, the dispute between the monogenists and the polygenists will die a silent and unobserved death.
One other question ought not to be passed over without notice, namely, whether, as is sometimes assumed, each sub-species or race of man has sprung from a single pair of progenitors. With our domestic animals a new race can readily be formed by carefully matching the varying offspring from a single pair, or even from a single individual possessing some new character ”

“ Even those who still believed in what is conventionally called "the inheritance of acquired characteristics" would be quick to repudiate any such application of the doctrine as is commonly made by most of the philanthropists and social workers who are proceeding without seeking the light of biology. But the idea that these modifications are inherited is so widespread among all who have not studied biology, and is so much a part of the tradition of society, that the question must be here examined, before we can proceed confidently with our program of eugenics. ”

“ Thus in our example that group of individuals would alone survive, the ancestors of which originally possessed the appropriate colour. But if one group alone survived, it follows that all hereditary individual differences would have disappeared from the species, for the members of such a single group are identical with one another and with their original ancestors. We thus reach the conclusion that monogonic reproduction can never cause hereditary individual variability, but that, on the other hand, it is very likely to lead to its entire suppression. ”

“ In spite of these great and serious difficulties, we cannot here refrain from taking one more cursory glance at the ramification of the human pedigree, and at the same time considering, from the point of view of the theory of descent, the much discussed question of the monophyletic or polyphyletic origin of the human race, and its species or races. As is well known, two great parties have for a long time been at war with each other upon this question; the monophylists (or monogenists) maintain the unity of origin and the blood relationship of all races of men. ”

“ The Polygenists regard the differences of height, features, and colour, which distinguish the inhabitants of different countries of the globe, as fundamental; the Monogenists consider these differences merely as the result of accidental conditions, which have modified, in various degrees, a primitive type. The former hold that there are several human species perfectly independent of each other; the latter that there is but one species of man which is divided into several races, all of which are derived from a common stock. ”

“ The monogenists had, strictly speaking, a right to do so without any violence to their principles; but the polygenists, who have followed their example, have sinned against logic. The former attribute all varieties of the human species to the numerous modifications of five principal races, issued themselves from one common stock, and the same influences which, according to then, have in the origin produced fundamental races, have afterwards by an analogous process produced the secondary races. ”

“ These mutational forms are of several distinct and recognizable types which recur, and several of them breed true from their first appearance. The obvious difficulty, which in my judgment should make us unwilling at present to accept these occurrences as proof of the genesis of new species by mutation, is that we have as yet no certainty that the appearance of the new forms is not an effect of the recombination [Pg 102] of factors, such as is to be seen in so many generations of plants derived from a cross involving many genetic elements. The first question is what is Oenothera Lamarckiana? ”

“ But the experience of the practical breeder does, I think, on the whole, support the contention to which systematists have so steadily clung under all the assaults of evolutionary philosophers, that, though we cannot strictly define species, they yet have properties which varieties have not, and that the distinction is not merely a matter of degree.
The first step is to discover the nature of the factors which by their complementary action inhibit the critical divisions and so cause the sterility of the hybrid. Thus expressed, we see the problem of inter-specific sterility in its right place ”

“ This leaves the question of man's ultimate origin completely open to speculation, and enables both monogenists and polygenists to contend for their respective views with plausible arguments, and without fear 405 of being refuted by facts. Polygeny, or plural origins, would at first sight seem to be the most plausible theory to account for the great diversities of human races actually existing, and which can be shown to have existed from such an immense antiquity. ”

“ When materials began to accumulate they were detrimental to the polygenist theory. Especially was this the case with regard to the proof of what Broca termed “eugenesis”—i.e., that all the Hominidæ are, and always have been, fertile with each other. This, which formed a test between species and varieties in Botany and Zoology, was claimed also in Anthropology, and the polygenists had to seek for support elsewhere. They found it in Linguistics; “language as a test of race” bulked large in ethnological controversy, and is not yet entirely extinct. ”

“ No, reply the polygenists; for the differences are greater than those which characterize certain species. In order to meet this objection, the monogenists have had recourse to what is called the middle theory, and to that of the cross-breeds. The whole of the external circumstances under which the representatives of a species exist, constitute what is called the middle or medium, to which monogenists, supporting themselves on undoubted facts, attribute the power of gradually changing the medium type of a species. ”

“ Like the Monogenists, the Polygenists are of several sects; some imagine that their assumed species of mankind were created where we find them—the African in Africa, and the Australian in Australia, along with the other animals of their distributional province; others conceive that each species of man has resulted from the modification of some antecedent species of ape—the American from the broad-nosed Simians of the New World, the African from the Troglodytic stock, the Mongolian from the Orangs.
The first hypothesis is hardly likely to win much favour. ”

“ We do not know how widespread recessive genes are in the human germ-plasm. The fact that defective individuals appear in certain communities may be safely interpreted to mean that individuals bearing the same gene have at last come together. On the other hand, the absence of such individuals from the community, at large, may only mean that the chance of suitable combinations is small, and does not mean necessarily that the gene in question is confined to the community within which the defects have been recorded. ”

“ These go over into the first generation hybrids, and are sorted out in the germ cells of the hybrid. Consequently, when the F1’s are inbred, there are all sorts of recombinations of the minor factors. This explains the greater variability of the second generation.
It is probable that in most of our domesticated animals, including man, much of the variability is due to multiple factors, which makes a study of inheritance in these groups extremely difficult, especially when, as in the case of man, the number of offspring from a pair is small, and critical combinations for study can not be made. ”

“ In man and in domesticated animals we find that individuals appear occasionally that are defective in one or another respect. Some of the defects are inherited. Rarely a new one appears that has not been seen before. But the majority of them are reappearances of characters that have been carried under the surface as recessive genes in the germ-plasm. Today we recognize that each of these modifications, if recessive, has first arisen as a mutational change in a single gene before it appeared on the surface as a character by the coming together of two such genes. ”

“ In affirming the probability of a polygenetic origin of species, there is no intention of asserting that all species originate in this way. It seems evident that a very large number of species of restricted range are certainly monogenetic, at least as far as origin in space is concerned. It is possible that any species may arise at two or more distinct times. Polygenesis can occur readily only in species of more or less extensive area, in which recur instances of the same or similar habitat. ”

“ Two schools are to be found in anthropology; one called that of the Polygenists, the other that of the Monogenists,5 two words which came from America, and which we receive because they have the great advantage of being clear and precise, determining, by the opposing point of their doctrines, two distinct schools, the one recognising but one family in the human race, of which some members have alone preserved the primitive type—altered everywhere else; the other school recognising no direct relationship among the races of mankind. The Polygenistic school is comparatively modern ”

“ But now the question arises,—How can we explain the presence of such characters consistently with a belief in the continuity of the germ-plasm, a theory which implies the rejection of the supposition that acquired characters can become hereditary? How can the individuals of any species come to possess various characters which are undoubtedly hereditary, if all changes which are due to the influence of external conditions are transient and disappear with the individual in which they arose? ”

“ Hence whatever we learn about those hereditary elements that stand for defects, we learn just as much about the behavior of the normal partners of those elements. In a word, heredity is not confined to a study of the shuffling of those genes that produce abnormal forms, but is equally concerned with what is going on when normal genes are redistributed. This method of pitting one gene against the other furnishes the only kind of information relating to heredity about which we have precise knowledge. ”

“ Consequently, polygenists must admit that the species of which their human genus is composed could not have come into existence in every place where man is now found, unless they wish to make a striking exception of this human genus. ”

“ If one can control the matings, so that out-breeding takes place each time, the result would undoubtedly be like that in our diagram; but what chance is there for a recessive character, that is neither beneficial nor injurious, if left to itself, to contaminate widely the race with its gene? The answer is that for any one defect there is hardly any chance at all. On the other hand, there is always a possibility that a defect may become widespread despite the chances against each in turn. ”

“ But what becomes of their argumentation, if it be proved that all intermixtures are not eugenistic, that is to say, that certain mongrels are not between themselves indefinitely prolific; that other cross-breeds become sterile in the first generation; and, finally, that certain races are so little homogenesic, that the birth of cross-breeds of the first degree is more or less exceptional? If one of these propositions can be effectually established, the monogenists would have little cause to congratulate themselves for having appealed to physiology. ”

“ As is well known, anthropologists are divided into two absolutely distinct camps: the Polygenists, who claim that differences of species evidenced by differences in height, in features, and in complexion, are the result of the springing of the human race from different progenitors ”

“ It is for these reasons that many polygenists, after having proclaimed the multiplicity of the origins of humanity, and having recognised the impossibility of determining the number and the characters of the primitive stocks, have justly avoided methodically to divide the human genus into species. ”

“ The majority cling to their belief in the Lamarckian factors.
The only safe conclusion to which we can come is that the question as to inheritance of acquired characters has still to be answered.
Evolution depends on Variation and Heredity. The problems of Variation and Heredity are now being attacked from many sides by biologists. It is on their solution that all advance in future must depend. ”