Читать книгу Race, Language and Culture - Boas Franz - Страница 10

Table of Contents

For determining the characteristics of a population knowledge of the laws of heredity is indispensable. Ordinarily the term heredity in relation to racial^[9] characteristics is used in a somewhat loose manner, and we should distinguish clearly between the hereditary stability of a population and the hereditary characteristics which determine the bodily form and functions of an individual. The concept of hereditary stability in a population can mean only that the distribution of forms which occur in one generation will be repeated in exactly the same way in the following generation. This is clearest in the case of a homogeneous population as defined before. In every population varying bodily forms of individuals will occur with characteristic frequencies. In an undisturbed homogeneous population we must necessarily assume that each generation will show the same characteristic distribution of individual forms. If it did not do so there would be a disturbance of the hereditary stability.

Conditions are quite different in a heterogeneous population like that of the United States. Owing to intermarriages between the various constituent types there must be a tendency toward greater homogeneity, setting aside, of course, the influx of new immigrants. Experience shows that no matter how rigid may be the social objection to intermarriages between different groups, or how strong the pressure to bring about marriages between members of the same group, they will not prevent the gradual assimilation of the population. An instance of this kind is presented by the castes of India in Bengal. Notwithstanding the rigid endogamy of castes it has been observed that the highest castes are similar in type to the peoples of Western Asia, while the lower down in the scale of castes we go the more this type becomes mixed with the older substratum of the native population.^[10] This can be explained only by intermarriage between the different castes which must have occurred notwithstanding the rigid laws forbidding it. The less the tendency toward segregation of different groups, the more rapid will be the approach toward homogeneity. Therefore notwithstanding the laws of hereditary stability in individual strains, there cannot be a hereditary stability of a heterogeneous population until homogeneity has been attained. It may even be considered doubtful whether a disturbance of the distribution of bodily forms may not occur as an effect of the intermingling of two populations similar or even identical in type, but of different ancestry, in which, therefore, a heterogeneity of ancestry exists.^[11]

Thus it will be seen that the physiological laws of heredity are quite different from the statistical expression of the effects of heredity upon a large population. The latter depends upon both the biological laws of heredity and the peculiar social structure of the population which is being considered. These two aspects of heredity must be kept clearly apart.

Unfortunately, the laws of heredity in man are not clearly known, and it is not yet possible without overstepping the bounds of sound, critical, scientific method to apply them to the study of the characteristics of a population. A considerable amount of preliminary fundamental work must be done before we can proceed to the explanation of special complex phenomena. One fundamental point of view may be considered as established, namely, that when a definite couple of parents is given, the probability of occurrence of a given form among the descendants of this couple is fixed. In man it is not easy to demonstrate this fact because the number of children for each couple is small. If we assume, however, an organism in which each parental couple has an infinitely large number of offspring, the laws of heredity may be so expressed that each form that occurs among the offspring has a definite probability. In man these laws can be investigated only by combining many families in which both parents, or at least one of the parents, has the same characteristic form, although in this case the phenomenon is obscured by the fact that the same form in the parent does not necessarily mean the same ancestry.^[12] Observation of various features of the body of man shows that the simple forms of Mendelian heredity are not often applicable. It is true that in a number of cases of pathological modifications, the validity of the simple Mendelian formulas has been established. Even in these cases the number of observations is not sufficient to determine whether we are dealing with exact Mendelian ratios or with approximations. Practically all other cases are still open to doubt. Even in the case of eye color, which has been claimed to be subject to a simple Mendelian ratio with dominance of brown over blue, the available figures are not quite convincing.^[13] For the more complex variable measurements of the body simple Mendelian ratios are certainly not applicable. Up to the present time the complex laws governing the frequencies of occurrence of bodily forms among descendants of an ancestral line are not known.

The investigation of any population must, therefore, take into consideration the detailed study of the laws of heredity.

[9]	The terms “race” and “racial” are here used in the sense that they mean the assembly of genetic lines represented in a population.

[10]	H. H. Risley and E. A. Gait, “Census of India, 1901” (Calcutta, 1903), vol. 1, pp. 489 et seq.

[11]	M. D. and Raymond Pearl, “On the Relation of Race Crossing to the Sex Ratio,” Biological Bulletin, vol. 15 (1908), pp. 194 et seq.

[12]	Franz Boas, “On the Variety of Lines of Descent Represented in a Population,” loc. cit.

[13]	Helene M. Boas, “Inheritance of Eye Color in Man,” American Journal of Physical Anthropology, vol. 2 (1919), pp. 15 et seq.