What remains is the possibility of making an accurate survey of the living races in the hope that the relationships which a classification brings out may indicate something as to the former development of the races. If for instance it could be established that the Ainu or aborigines of Japan are closely similar in their bodies to the peoples of Europe, we would then infer that they are a branch of the Caucasian stock, that their origin took place far to the west of their present habitat, and that they have no connection with the Mongolian Japanese among whom they now live. This is working by indirect evidence, it is true; but sooner or later that is the method to which science always finds itself reduced.
The desirability of a trustworthy classification of the human races will therefore be generally accepted without further argument. But the making of such a classification proves to be more difficult than might be imagined. To begin with, a race is only a sort of average of a large number of individuals; and averages differ from one another much less than individuals. Popular impression exaggerates the differences, accurate measurements reduce them. It is true that a Negro and a north European cannot possibly be confused: they happen to represent extreme types. Yet as soon as we operate with less divergent races we find that variations between individuals of the same race are often greater than differences between the races. The tallest individuals of a short race are taller than the shortest individuals of a tall race. This is called overlapping; and it occurs to such an extent as to make it frequently difficult for the physical anthropologist to establish clear-cut types.
In addition, the lines of demarcation between races have time and again been obliterated by interbreeding. Adjacent peoples, even hostile ones, intermarry. The number of marriages in one generation may be small; but the cumulative effect of a thousand years is often quite disconcerting. The half-breeds or hybrids are also as fertile as each of the original types. There is no question but that some populations are nothing but the product of such race crossing. Thus there is a belt extending across the entire breadth of Africa of which it is difficult to say whether the inhabitants belong to the Negro or to the Caucasian type. If we construct a racial map and represent the demarcation between Negro and Caucasian by a line, we are really misrepresenting the situation. The truth could be expressed only by inserting a transition zone of mixed color. Yet as soon as we allow such transitions, the definiteness of our classification begins to crumble.
In spite of these difficulties, some general truths can be discovered from a careful race classification, and certain constant principles of importance emerge from all the diversity.
22. Traits on Which Classification Rests
Since every human being obviously possesses a large number of physical features or traits, the first thing that the prospective classifier of race must do is to determine how much weight he will attach to each of these features.
The most striking of all traits probably is stature or bodily height. Yet this is a trait which experience has shown to be of relatively limited value for classifactory purposes. The imagination is easily impressed by a few inches when they show at the top of a man and make him half a head taller or shorter than oneself. Except for a few groups which numerically are rather insignificant, there is no human race that averages less than 5 feet in height. There is none at all that averages taller than 5 feet 10 inches. This means that practically the whole range of human variability in height, from the race standpoint, falls within less than a foot. The majority of averages of populations do not differ more than 2 inches from the general human average of 5 feet 5 inches.
Then, too, stature has been proved to be rather readily influenced by environment. Each of us is a fraction of an inch taller when he gets up in the morning than when he goes to bed at night. Two races might differ by as much as a couple of inches in their heredity, and yet if all the individuals of the shorter race were well nourished in a favorable environment, and all those of the taller group were underfed and overworked, the naturally shorter race might well be actually the taller one.
The cephalic index, which expresses in percentage form the ratio of the length and the breadth of the head, is perhaps the most commonly used anthropological measurement.[4] It has certain definite advantages. The head measurements are easily made with accuracy. The index is nearly the same on the living head and on the dead skull; or one is easily converted into the other. This enables present and past generations to be compared. The index is also virtually the same for men and for women, for children and for adults. Finally, it seems to be little affected by environment. The consequence is that head form has been widely investigated. There are few groups of people of consequence whose average cephalic index we do not know fairly accurately. The difficulty about the cephalic index from the point of view of race classification is that it does not yield broad enough results. This index is often useful in distinguishing subtypes, nation from nation, or tribe from tribe; but the primary races are not uniform. There is, for instance, no typical head form for the Caucasian race. There are narrow headed, medium headed, and broad headed Caucasians. The same is true of the American Indians, who are on the whole rather uniform, yet vary much in head form.
The nasal index, which expresses the relation of length and breadth of nose, runs much more constant in the great races. Practically all Negroids are broad-nosed, practically all Caucasians narrow-nosed, and the majority of peoples of Mongolian affinities medium-nosed. But the nasal index varies according to the age of the person; it is utterly different in a living individual and a skull;[5] it seems to reflect heredity less directly than the cephalic index; and finally it tells us nothing about the elevation or profile or general formation of the nose.