Part 4

These facts relating to growth are of fundamental importance for a correct interpretation of the oft-discussed phenomena of early arrest of growth. We have seen that among members of the same race a prolonged period of growth goes hand in hand with unfavorable development, while an abbreviated period of growth results in larger dimensions of all physical measurements, and in a superiority of mental activity. In this statement pathological cases of complete premature arrest of development, or of over-development, are of course excluded,—cases of dwarfish growth or of microcephaly, as well as cases of hypertrophic growth of organs. It follows, that, in judging the physiological value of arrest of growth, the mere fact that growth ceases in one race at an earlier time than in another cannot be considered as significant in itself without observations on the rapidity of growth.

So far, the question still remains open, in how far there may be changes in the types of man that cannot be explained by acceleration or retardation of growth.

An attempt has been made by Rieger to explain differences in head-form as due to the effect of physiological and mechanical conditions, and Engel emphasizes the effect of pressure of the muscles upon the forms of the head. Walcher tries to explain different head-forms by the consideration of the position of the infant in the cradle. He believes that position on the back produces round heads; position on the side, long heads. It would seem, however, that the difference of head-form in large areas of Europe, in which infants are treated in the same manner, are too great to make this explanation acceptable.

A number of observations have been made, however, which demonstrate conclusively a difference between urban and rural types. These observations were first made by Ammon, who showed that the urban population in Baden differs from the rural population in head-form, stature, and pigmentation. He accepts the conclusion that we have here an actual change in type; due, however, not to a direct effect of environment, but rather to an elimination of certain types in city life: in other words, an effect of natural selection. This observation is in accord with observations made by Livi in the cities of Italy, which show also a difference when compared to the surrounding country. Comparisons of the normal and hospital populations of London, made by Shrubsall, are not unfavorable to the assumption of a certain amount of correlation between morbidity and physical type, although the homogeneity of material from a metropolis like London, drawn from different social strata of a large city, remains always open to doubt.

Another explanation, given by Livi, seems to account adequately for the difference between city and country population, without necessitating the assumption of any considerable effect of natural selection, which presupposes an improbable correlation between mortality and fertility on the one hand, and traits like head-form and pigmentation on the other. The change of type in cities, so far as it has been observed, is of such character, that the city always shows greater resemblance to the average type of the whole large district in which it is located. If the local rural population is markedly short-headed, the general type over a larger area from which the city population is drawn more long-headed, then the city population will be more long-headed, and _vice versâ_. Unless selection can be demonstrated to occur in a sufficient number of definite families, this explanation seems simpler and adequate.

Up to quite recent times no evidence of actual changes of type was available, except the observations by Ammon and those by Livi on the physical characteristics of rural and urban populations, to which I have just referred, and some others on the influence of altitude upon physical form. In the discussions of the distribution of different types of man in Europe, peculiarities of body-form in certain areas—as in the mountains of central France, in parts of Tuscany, in the province of Zealand in Holland, in southwestern Norway—have been explained as due to the survival of old racial types, to the influence of natural selection, or to the direct influence of environment, according as the necessities of the case prompted the investigator to adduce the one cause or the other, or a combination of any two or of all, as a convenient explanation of the difficult phenomenon (Ripley). It goes without saying that haphazard application of unproved though possible theories cannot serve as proof of the effectiveness of selection or of environment in modifying types. The effectiveness of selection can be proved only by an investigation of the surviving members of a type as compared to those eliminated by death, or of a shifting of population connected with the selection of a certain type. The influence of environment requires the direct comparison of parents living under one environment with children living under another environment.

I cannot give any example in which the influence of selection has been proved beyond cavil. It seems plausible that in the criminal colonies of earlier periods, and in the settling of the West by the most vigorous members of our Eastern population, and in the complementary weeding-out of strong elements in some parts of New England, this principle may have been active; but we have no actual data which would connect with physical types the selection that has undoubtedly taken place.

On the other hand, it has been my good fortune to be able to demonstrate the existence of a direct influence of environment upon the bodily form of man by a comparison of immigrants born in Europe and their descendants born in New York City (Boas). I have investigated four groups of people,—the South Italians, representing the Mediterranean type of Europe, which is characterized by short stature, elongated head, dark complexion and hair; the Central European type, which is characterized by medium stature, short head, light hair and lighter complexion; the Northwest European type, which is characterized by tall stature, elongated head, light complexion, and blond hair. Furthermore, I have investigated an extended series of East European Hebrews, who resemble in some respects the Central European group. The traits which I selected for examination are head-measurements, stature, weight, and hair-color. Among these, only stature and weight are closely related to the rate of growth, while head-measurements and hair-color are only slightly subjected to these influences. Differences in hair-color and head-development do not belong to the group of measurements of which I spoke before, which depend in their final values upon the physiological conditions during the period of growth. From all we know, they are primarily dependent upon heredity.

The results of our inquiry have led to the unexpected result that the American-born descendants of these types differ from their parents; and that these differences develop in early childhood, and persist throughout life. It is furthermore remarkable that each type changes in a peculiar way. The head of the American-born Sicilian becomes rounder than that of the foreign-born. This is due to a loss in length and an increase in width. The face becomes narrower, the stature and weight decrease. The head of the American-born Central European loses both in length and width, more so in width, and thus becomes more elongated. The face decreases very much in width; stature and weight increase. The modifications of the American-born descendants of the Scotch type are not marked, except that stature and weight increase. The American-born Hebrew has a longer and narrower head than the European-born; the head is therefore considerably more elongated. His face is narrower; stature and weight are increased. In none of the types have marked differences in color of hair between American-born and foreign-born been found.

In order to understand the causes which bring about these alterations of type, it is necessary to know how long a time must have elapsed since the immigration of the parents before a noticeable change of type of the offspring is brought about. This investigation has been carried out mainly for the cephalic index, which, during the period of growth of the individual, undergoes only slight modifications. The investigation of the Hebrews shows very clearly that the cephalic index of the foreign-born is practically the same, no matter how old the individual at the time of immigration. This might be expected when the immigrants are adult or nearly mature; but it is of interest to note that even children who come here when one year or a few years old develop the cephalic index characteristic of the foreign-born. This index ranges around 83. When we compare the value of this index with that of the index of the American-born, according to the time elapsed since their immigration, we find a sudden change. The value drops to about 82 for those born immediately after the immigration of their parents, and drops to 79 in the second generation; i.e., among the children of American-born children of immigrants. In other words, the effect of American environment makes itself felt immediately, and increases slowly with the increase of time elapsed between the immigration of the parents and the birth of the child.

The conditions among the Sicilians and Neapolitans are quite similar to those observed among the Hebrews. The cephalic index of the foreign-born remains throughout on almost the same level. Those born in America immediately after the arrival of their parents show an increase of the cephalic index. In this case, the transition, although rapid, is not quite so sudden as among the Hebrews, probably because among those born a year before or after immigration there is some doubt as to the place of their birth. These uncertainties are due to the habit of the Italians to migrate back and forth between Italy and America before finally settling here, and to the indefiniteness of their answers in regard to the places of birth of the child, which sometimes had to be inferred from the age of the child and the year of immigration of the mother. As long as this uncertainty exists, which is hardly present at all in the data relating to the Hebrews, it does not seem necessary to assume any other cause for the more gradual change of the cephalic index about the time of immigration.

The Italian immigration is so recent, that individuals who were born many years after the arrival of their parents in America are very few in number, and no individuals of the second generation have been observed. For this reason it is hardly possible to decide whether the increase of the cephalic index continues with the length of time elapsed between the immigration of the parents and the birth of the child.

The explanation of these remarkable phenomena is not easy. Whatever their causes may be, the change in form cannot be doubted. It might, however, be claimed that the changes are not due to deep physiological causes, but to the changes of certain external factors. The composition of the immigrant population might be such that the people who came here at different periods had distinct physical characteristics, and that these are now reflected in the descendants of the older generations when compared with the more recent immigrants. It can be shown, however, that the differences between the Hebrews who immigrated at different periods between 1860 and 1909 are so slight that they cannot account for the type of the descendants of immigrants. This important point can be elucidated more definitely by the application of a different method. For this purpose I have compared the cephalic index of all immigrants of a certain year with that of their descendants. It appears from these comparisons that the differences which are exhibited by the whole series exist also between the immigrants who arrived here in a certain year and their descendants. This purely statistical explanation of the phenomenon may therefore be dismissed.

More difficult to investigate is the hypothesis that the mechanical treatment of infants may have a decided influence upon the form of the head, and that the changes in cradling and bedding which are made by some immigrants almost immediately after their arrival in America account for the changes of head-form. If this were true, the continued changes among the Hebrews might indicate merely that the American method of cradling is used the more frequently, the longer the family has resided in this country. A number of investigators have claimed that the position of the child on the back tends to produce short-headedness, and that the position on the side tends to produce long-headedness (Walcher). There is good evidence that a flattening of the occiput occurs when a very hard pillow is used and the child lies permanently on its back. This is the case, for instance, among many Indian tribes, and similar results might obtain if a swathed child were to lie permanently on its back. The prevalence of rachitis in New York would favor distortion due to pressure.

While I cannot disprove the existence of such influences, I think weighty considerations are against their acceptance. If we assume that among the Hebrews the children born abroad have a lesser length of head than those born here because they are swathed and lie more permanently on their backs than the American-born children, who can move about freely, we must conclude that there is a certain compensatory decrease in the other diameters of the head of the American-born. Since this compensation is distributed in all directions, its amount in any one direction will be very small (Boas).

The decrease in the width of head that has been observed is so large that it cannot be considered simply as an effect of compensation; but we have to make the additional hypothesis that the American-born children lie so much on their sides that a narrowing of the head is brought about by mechanical pressure. The same considerations hold good in all the other types. If, therefore, in one case the greater freedom of position of the child increases the length of its head, it is difficult to see why, among the Bohemians, the same causes should decrease both horizontal diameters of the head, and why, among the Sicilians, the length should decrease, the width increase.

The development of the width of the face seems to my mind to show most clearly that it is not the mechanical treatment of the infant that brings about the changes in question. The cephalic index suffers a very slight decrease from the second year to adult life. It is therefore evident that children who arrive in America very young cannot be much affected by American environment in regard to their cephalic index. On the other hand, if we consider a measurement that increases appreciably during the period of growth, we may expect that in children born abroad but removed to America when young, the total growth may be modified by American environment. The best material for this study is presented by the Bohemians, among whom there are relatively many full-grown American-born individuals. The width of face of Bohemians, when arranged according to their ages at the time of immigration, shows that there is a loss among those who came here as young children,—the greater, the younger they were. Continuing this comparison with the Americans born one, two, and more years after the arrival of their mothers, the width of face is seen to decrease still further. It appears, therefore, that the American environment causes a retardation of the growth of the width of face at a period when mechanical influences are no longer possible.

I have not carried through the analogous investigation for stature, because in this case the increase might simply be ascribed to the better nutrition of most of the north and central European immigrants after their immigration into this country.

There is another hypothesis which might account for the observed changes of type. If it were assumed that among the descendants of immigrants born in America there are an appreciable number who are in reality children of American fathers, not of their reputed fathers, a general assimilation by the American type would occur. Socially this condition is not at all plausible; but, on account of the importance of the phenomenon that we are discussing, it should be considered. I do not think that any of the observations that have been made are in favor of this theory. The changes that occur in the Bohemians who arrive here as young children, the different directions of the changes in distinct types, particularly the shortening of the head of Bohemians and of Italians, do not favor the assumption. Furthermore, if the modifications were due to race-mixture, the similarity between fathers and American-born children should be less than the similarity between fathers and foreign-born children, but there is no indication that this is the case.

This hypothesis is also shown to be untenable by the comparisons of fathers and mothers with their own foreign-born children. These comparisons show that the differences are the same in the case of fathers and children, and of mothers and children; so that obviously the same conditions must control the relations between fathers and their children, and mothers and their children. In other words, the fathers must be considered as the true fathers of their children.

Earnest advocates of the theory of selection might claim that all these changes are due to the effects of changes in death-rate among foreign-born and American-born; that either abroad or here individuals of certain types are more liable to die, and that thus these changes are gradually brought about. On the whole, it seems to my mind, the burden of proof would be entirely on those who claim such a correlation between head-index, width of face, etc., and death-rate,—a correlation which I think is highly improbable, and which could be proposed only to sustain the theory of selection, not on account of any available facts. I grant the desirability of settling the question by actual observations; but, until these are available, we may point out that the very suddenness of the changes after immigration, and the absence of changes due to selection by mortality among the adult foreign-born, would require such a complicated adjustment of cause and effect in regard to the correlation of mortality and bodily form, that the theory would become improbable on account of its complexity.

It would be saying too much to claim that all the distinct European types become the same in America, without mixture, solely by the action of the new environment. First of all, I have investigated only the effect of one environment, and there is every reason to believe that a number of distinct types are developing in America; but we will set aside this point, and discuss only our New York observations. Although the long-headed Sicilian becomes more round-headed in New York, the round-headed Bohemian and Hebrew more long-headed, the approach to a uniform general type cannot be established, because we do not know yet how long the changes continue, and whether they would all lead to the same result. I confess, I do not consider such a result as likely, because the proof of the plasticity of types does not imply that the plasticity is unlimited. The history of the British types in America, of the Dutch in the East Indies, of the Spaniards in South America, favors the assumption of a strictly limited plasticity. Certainly our discussion should be based on this more conservative basis until an unexpectedly wide range of variability of types can be proved. It is one of the most important problems that arise out of this investigation, to determine how far the instability or plasticity of types may extend.

Whatever the extent of these bodily changes may be, if we grant the correctness of our inferences in regard to the plasticity of human types, we are necessarily led to grant also a great plasticity of the mental make-up of human types. We have observed that features of the body which have almost obtained their final form at the time of birth show modifications of great importance in new surroundings. We have seen that others which increase during the whole period of growth, and are therefore subject to the continued effect of the new environment, are modified even among individuals who arrived here during their childhood. From these facts we must conclude that the fundamental traits of the mind, which are closely correlated with the physical condition of the body, and whose development continues over many years after physical growth has ceased, are the more subject to far-reaching changes. It is true that this is a conclusion by inference; but if we have succeeded in proving changes in the form of the body, the burden of proof will rest on those who, notwithstanding those changes, continue to claim the absolute permanence of other forms and functions of the body.

In order to gain a correct understanding of the importance of changes in the frame of the human body, it seems desirable to view the type of modern man from a somewhat different standpoint.

It is quite a number of years since Fritsch, in his studies of the anthropology of South Africa, pointed out that a peculiar difference exists in the form of the body of the Bushman and the Hottentot as compared to that of Europeans, in that the former exhibit slenderer forms of the bones, that the bone is very solid in its structure; while in the European the skeleton appears heavier, but of more open structure. Similar differences may be observed in a comparison between the skeletons of wild animals and those of domesticated animals; and this observation has led to the conclusion that the Bushmen are in their physical habitus to a certain extent like wild animals, while the Europeans resemble in their structure domesticated animals.

This point of view—namely, that the human race in its civilized forms must be compared, not with the forms of wild animals, but rather with those of domesticated animals—seems to me a very important one; and a somewhat detailed study of the conditions in which various races are found suggests that at the present time, even among the most primitive types of man, changes incident to domestication have taken place almost all over the world.

There are three different types of changes due to domestication which must be clearly distinguished. On the one hand, the bodies of domesticated animals undergo considerable transformations, owing to the change in nutrition and use of the body. On the other hand, selection and crossing have played an important part in the development of races of domesticated animals.