We will now turn to the consideration of another element which determines the physical type of man. Although we have seen that environment, particularly domestication, has a far-reaching influence upon the bodily form of the races of man, these influences are of a quite secondary character when compared to the far-reaching influence of heredity. Even granting the greatest possible amount of influence to environment, it is readily seen that all the essential traits of man are due primarily to heredity. The descendants of the negro will always be negroes; the descendants of the whites, whites; and we may go even considerably further, and may recognize that the essential detailed characteristics of a type will always be reproduced in the descendants, although they may be modified to a considerable extent by the influence of environment. I am inclined to believe that the influence of environment is of such a character, that, although the same race may assume a different type when removed from one environment to another, it will revert to its old type when replaced in its old environment. This point has not been proved by actual anthropological evidence; but it seems reasonable to make this assumption by analogy with what we know of the behavior of plants and animals. It would, of course, be highly desirable to clear up this question by appropriate investigations.

In order to obtain a clearer understanding of the racial problem, it seems necessary to describe more definitely the characteristics of heredity. In the discussion of modern anthropology, two theories have been advocated relating to the manner in which parental traits are inherited by children. Francis Galton and his adherents have assumed that the form of the body of an individual is determined by the racial type to which the parents belong, modified, however, by the tendency of reversion to a type intermediate between the special variations presented by the parents. When, for instance, the father of an individual is unusually tall, his mother somewhat taller than the average, it is assumed that the tendency of the children would be to develop a stature which is somewhat near the general type, but at the same time dependent upon the intermediate value located between the stature of the mother and that of the father. On the other hand, the development of the Mendelian doctrine (Lock, Bateson) of heredity has led other investigators to assume that the offspring of two distinct types may be a mixed type, but that his descendants will tend to revert either to one parental type or to the other, or that one of the parental types may dominate over the influence of the other parental type. Investigations relating to this problem are not very numerous; but, on the whole, it would appear that the results so far obtained are in favor rather of a modified form of Mendelian inheritance than of an inheritance characterized by reversion of the children to a middle type between the parents, or to a type dependent upon such a middle type.

A number of years ago I had an opportunity to investigate a considerable number of Indian half-bloods; that is to say, of descendants of Indian mothers and white fathers. The most characteristic difference between the American Indian race and the European race, so far as these differences can be expressed in metrical form, is found in the width of the face. An extensive series of measurements of width of face made among half-bloods showed conclusively that the width of face does not tend to range around a certain intermediate value located between the width of face of the white race and that of the Indian race, but there was a decided tendency in the children to resemble either the Indian race or the white race; in other words, that feature of Mendelian inheritance which brings about the occurrence of mixed characteristics in the first hybrid generation was not found, but instead of this a decided tendency of reversion to either type, and to comparative rarity of intermediate forms. The results seem also to indicate that the Indian form in this mixture seems to dominate over the white form, but not in the Mendelian sense, which would require the presence of dominant features in a certain definite number of individuals, but only in the sense that the Indian type was a little more frequent than the European type, with the effect that the average width of face of the whole series was a little nearer to the Indian group than to the white group.

While this single observation is not by any means sufficient to determine fully the characteristic traits of heredity which govern the phenomenon in question, they indicate decidedly and beyond cavil that, in this case at least, we find what has been called by Karl Pearson “alternating inheritance.” It is worth remarking that not all the features of the body of the half-blood Indian exhibit the same tendency; that, for instance, in the case of stature, a general increase in the stature of the mixed people over that of the pure races may be observed.

Attention has been called by Felix von Luschan to a similar phenomenon which occurs in the mixed population of southern Asia Minor, where he believes to have found an alternating inheritance of the head-form, particularly of the proportions between width and length of head; some of the people retaining the short, high head-forms of the Armenoid type of the interior of Asia Minor, while the others have the long, low head of the Semites of Syria.

For a clear understanding of the laws of heredity, it seems important to know whether a similar alternating inheritance occurs in marriages of members of the same type. I have been enabled to investigate this question by a study of the East European Hebrews living in New York. A simple consideration shows, that, if the children tend to follow a type intermediate between the type of their parents, then the children of one family will show the same degree of resemblance among themselves, no matter how great the difference between the parents; for, if they simply tend to reproduce a middle type, it would not make any difference whether the mother is excessively short and the father excessively tall, or whether both parents are of middle stature. In both of these cases the intermediate value would be the same, and we should therefore expect that the effect upon the children would be the same. If, on the other hand, there is any kind of alternation in inheritance, the effect upon the family would be quite different. We should expect, in a family of which both parents are near the typical average, to find the children also to be near this average. On the other hand, if the mother is excessively short and the father excessively tall, we should expect some of the children to follow the mother in regard to shortness of stature, others to follow the father in regard to tallness. It will therefore be seen that in the case of alternating inheritance, we must expect an increased variability among the children. The compilation of material obtained from several thousand families shows very definitely that the variability among children both of whose parents belong to the same racial type, even to the same local type, increases quite considerably with the increased difference of the parents; so that we may assume a decided tendency to alternating inheritance in these cases. There is, however, no evidence whatever of the dominance of one type over another.

Quite a number of investigations have been made in relation to the intensity of heredity of parents and of grandparents; and, notwithstanding the uncertainty of the quantitative result, it seems reasonably certain that the intensity of heredity for each parent may be expressed by the value of about one-third (Pearson, Boas). It is somewhat difficult to explain clearly the significance of this value. I may, however, briefly indicate it in the following manner. Provided the mother differs in her stature by an amount of 9 cm. from the racial norm,—for instance, if she is 9 cm. taller than the average individual,—then we may expect the child to be one-third of 9 cm., or 3 cm., above the average. It will thus be seen that if both parents differ in the same direction from the average, the effect of both will be cumulative; and if both differ from the average of their people by the same amount, the joint effect of the two parents may be expressed by the coefficient of about two-thirds. In case, for instance, both father and mother should be 9 cm. above the type average, we should expect the child to be about two-thirds of 9 cm., or 6 cm., above the average.

Although definite information on the amount of heredity of previous generations is not yet available, the probability seems to be that the grandparents have jointly an influence of about two-ninths, the great-grandparents jointly of about two twenty-sevenths, etc., upon the offspring.

When we study these problems according to statistical theories, and take into consideration the observations on the resemblance of brothers and sisters, it can be shown that the theory of alternating inheritance cannot be taken too literally; for, if there were an absolute reversion of any one trait to pure ancestral types, we might say that the probability would be very small that two brothers should happen to repeat the bodily form of the same ancestor, because the number of ancestors in remote generations is very large. In other words, there must be an additional cause of resemblance between brothers and sisters. It is possible to show, that in case the inheritance has the strength denoted before, and if bodily form of a certain generation were due only to alternating inheritance acting from parents, grandparents, great-grandparents, and so on, and directly upon the generation in question, and without an occurrence of the same individuals in various places in the line of ancestors, then the resemblance between brothers and sisters, or, as we say, between the members of a fraternity, would result in a degree of resemblance which is much lower than the one actually observed. When the total number of ancestors is small, the recurrence of the same forms would become more probable, and the similarity of the series would increase. On the whole, the data seem to be best explained if we assume that there is not only alternating inheritance, but also a direct dependence upon the combination of the two parental types.

I should like to repeat here that these results have not been obtained with absolute certainty, and that it seems improbable that the laws of heredity in regard to various ancestral traits are the same. I do not enter into a discussion of the question of in how far these traits follow the laws of Mendelian inheritance,—a question that cannot be answered definitely at the present time (Davenport).

These problems have a fundamental importance for a clearer interpretation of the conditions which prevail in the form of local types of man.

In a large population which is as little stable in its habits as that of modern Europe and modern America, the number of ancestors of a single person increases very rapidly, the number of parents being two; of grandparents, four; of great-grandparents, eight; the theoretical number of ancestors twenty generations back would be over a million, or, more accurately, 1,048,576. Twenty generations represent, according to the rate of increase of modern times, about seven hundred years; according to the rate of increase of older times, about four hundred years as a minimum. These figures would apply to the series of generations represented by first-born males; for first-born females the respective numbers would be about five hundred years and three hundred and fifty years. If we consider, however, the actual descent of families, including individuals later born, we might perhaps assume that twenty generations in Europe would represent from eight hundred to nine hundred years, and among primitive peoples perhaps only little less, since in former times the differences between the rapidity of successive generations in Europe and among primitive peoples was not very great. This makes it obvious that it is entirely impossible that as great a number of ancestors as the theory requires can have contributed to the development of the individuals of the present generation. The reason for this is plain. Owing to intermarriages between the same families, large numbers of ancestors will be duplicated in different paternal and maternal lines; and in this way the real ancestry of each individual appears to be much more complex than the purely arithmetical treatment would suggest. The calculation for the ancestor table of the German Emperor, for instance, is instructive. According to O. Lorenz, the numbers of his ancestors in successive generations were as follows:—

A series of forty royal families gives the following averages:—

When we compare these conditions in the thickly populated parts of modern Europe and of America, with their unstable population, with the conditions among primitive tribes, it becomes at once apparent that the total number of ancestors of each type in small communities must be much less than the number of ancestors in the modern states just referred to. A characteristic example is presented by the Eskimo of Smith Sound in North Greenland. From all we know, it seems extremely unlikely that this community ever consisted of more than a few hundred individuals. From what we know about the history of Eskimo communities, we might much rather assume that originally it consisted of a very few families only. The community has been cut off from the outer world for very long periods; and while there may have been accessions of new individuals from outside once each century, on the whole it has remained completely isolated. It is therefore obvious that the ancestry of this group cannot contain anything like the million of people required by the theory, but that all the individuals must be interrelated through their remote ancestry.

Considering, now, the laws of inheritance as outlined before, it would appear that in a community of this type, the members of which number little more than two hundred individuals, the ancestor of every single individual from the eighth generation back must have been the same, because the eighth generation would require theoretically two hundred and fifty-six individuals,—a greater number than are actually found in the community; and the occurrence of any individuals who have not a good many near and remote ancestors in common with the whole rest of the community is highly improbable, if not impossible.

It follows from this at once that the variability of the whole series around its typical average must be rather small, because all the members of the group will have a certain amount of family resemblance. This uniformity of type will, of course, be the greater, the more uniform the ancestral group.

On the other hand, these conditions bring about another peculiar characteristic of the isolated group. Owing to the constant recurrence of the same ancestral types among the whole group, the type of the whole people becomes very similar to the characteristic traits of the small ancestral group; and the smaller this group, the stronger will be the probability of the type of the local group being quite distinct from the type of the whole people to which they belong.

It seems to my mind that these conditions explain to a considerable extent the occurrence of distinct local types in primitive races. When we find, for instance, that in North America a very marked type belongs to the Arctic coast of the continent, that a quite distinct type is found in the Mackenzie basin, still others in well-defined localities on the Pacific coast, again others in the Mississippi basin, one in the southeast, and one along the Rio Grande and in Mexico,—it seems plausible to ascribe their origin to the increase of small isolated groups, which, as we have seen, must necessarily lead to differentiation of type.

This view of the origin of local races is quite in accord with the remarkable results obtained by Johannsen in his studies of heredity. He repeated artificially the conditions which prevail in a small community, and exaggerated them by selecting types of equal form, and by propagating them by self-fertilization. He raised in this way bean-plants from beans of equal weight, and was able to restrict variation of the type, so that practically any kind of bean of particular weight and particular form could be bred true to the type of its ancestor, and without perpetuating the accidental variations of the ancestors. In cases where the ancestry goes back to a limited number of individuals, as among our isolated tribes, the variation will, of course, not be restricted to the same extent; but the characteristic development of a stable type is quite analogous to the experiment made by Johannsen.

Another phenomenon may be pointed out here which is still little investigated, but which deserves careful attention. We have seen that in stable communities in sparsely settled countries the relationship between members of a tribe will be quite close, and that this relationship will necessarily affect the type and its variability. In course of time two areas whose population has thus developed may be thrown into contact, and numerous intermarriages may occur. It will be seen at once, that, although the differences between the two types may be apparently only slight, a complete disturbance in the forms of heredity will result, because a great number of individuals of distinct ancestry are thrown together. To give an example. The South Italians and the Spaniards represent two types not very distinct in physical features, but separated for centuries. The small village communities of Italy, as well as those of Spain, have all the characteristics of communities in which endogamic marriages have been continued for a long period. In the Argentine Republic these two types come into contact and intermarry frequently. We have no observations on the result of this mixture upon physical characteristics, but it has been noted that the distribution of male and female births is quite different from that prevailing in families in which both parents are either Spanish or Italian (Pearl). It is also conceivable that this may be one of the elements bringing about the change of type of urban populations when compared to rural populations in Europe, and that it may have been active in the change of type observed among the descendants of European immigrants in America; for, although the observations have been made on pure types, in America cases of intermarriages of natives of different villages are much more common than in Europe.

After we have thus considered the influences of heredity and environment, so far as they determine the characteristics of distinct types of man, it remains to add a few words on the individuals constituting each type, and on the different distribution of individuals in distinct types.

I have had to refer repeatedly to the phenomena of variation in the races of man; and I have pointed out before, that, so far as individual features are concerned, we find that the range of variations in each human type is so great, that overlapping of the range of variation in different types is of constant occurrence. We have seen, for instance, that the medium brains of the Europeans occur with considerable frequency among negroes, and that only the excessively small negro brains have no parallel forms among the Europeans; and correspondingly that the excessively large European brains have no parallel forms among the brains of the negroes. The amount of variability in regard to various physical traits differs very considerably in different races. Most of the European types, for instance, are remarkable for their high variability. The same is true of the Polynesians and of some negro tribes. On the other hand, people like the European Hebrews, and, even more so, the North American Indians, are characterized by, comparatively speaking, much greater uniformity. The amount of variability differs considerably with regard to different physical features. It is, for instance, obvious that the hair-color and hair-form of North Europeans is much more variable than the hair-color and hair-form of the Chinese. In Europe the colors vary from flaxen to black, with a considerable number of individuals with red hair, and the form varies from straight to high degrees of waviness. Among the Chinese, on the other hand, we do not find equal variations in the darkness of color, since blondes and curly-haired individuals are absent. Similar observations may be made in regard to stature, head-form, or any other feature of the body that can be expressed by measurements.

The reason for the differences in variability is partly given in our previous remarks. We have seen, when a people is descended from a small uniform group, that then its variability will decrease; while on the other hand, when a group has a much-varied origin, or when the ancestors belong to entirely distinct types, the variability may be considerably increased. In all cases which have been investigated, even in those in which the variability is small, there still remain considerable differences in bodily appearance among the individuals constituting a tribal or national or other social unit; and what is true of the physical traits is obviously no less true of the mental traits, but it is difficult to express mental characteristics in numerical terms of variability. An acquaintance with tribes which are apparently on the simplest level socially, however, shows the existence of certain individuals of most diverse types of disposition and intellect; and as might be expected, if we consider mental condition as dependent upon bodily form, the great variability, even in the most uniform group, of the structure of the body, particularly of the brain, makes it plausible that very large differences in individual disposition may be expected.

What we have said before in regard to the overlapping of variations among different races and types, and the great range of variability in each type, may also be expressed by saying that the differences between different types of man are, on the whole, small as compared to the range of variation in each type.

The importance of these observations in the domain of mental development will be the subject of our future discussions.