THE PHYSICAL DISTINCTIONS OF MAN

OUR knowledge of the physical distinctions of man, which is basic for all work on the ever challenging problems of human evolution, requires constant revision and re-evaluation as more research material becomes available, new facts are discovered, and modern points of view are being developed. Generally speaking, the list of man's physical distinctions has been lengthened, whereas the significance of the single specific characters has diminished with advance in our understanding of man's true nature. Today there can be no longer any serious doubt that, in spite of all his many distinctions, man can and must be assigned a definite place within the order of primates among the Old World, or catarrhine, forms, he being most nearly related through one common ancestry to the anthropoid apes. From the latter man became distinguished chiefly in connection with his three outstanding specializations: the early and undoubtedly rapid acquisition of the erect posture, the later, gradual and ultimately great increase in relative brain-size, and the comparatively very recent prolongation of his main periods of life. Most investigators of man's physical distinctions have dealt with conditions as found in adults and frequently as represented by averages of only Europeans. This common and arbitrary limitation has resulted in various untenable claims in the enormous, old and new literature concerned with human peculiarities and has retarded the full appreciation of many of man's evolutionary inlovations. With the gradual accumulation of large series of monkeys and apes it has become possible to compare man with other primates on the basis of statistically adequate observations and at all stages of growth. Only in this way can it be decided whether a particular character is really distinctive in all cases within a representative, normal range of variations, or differs merely in regard to the frequency of its occurrence, thus being of lesser significance. With the realization that any evolutionary change, apparent in the adult, is the result of some primary alteration in the processes of growth and development, it seems highly desirable to discover the conditions in which human growth differs from the growth of non-human primates. By finding the ontogenetic distinctions of man his distinctions at the completion of growth will become better understood. A large variety of the innumerable specializations in human ontogeny has already been reviewed in another publication by the writer (1949). The present paper is an attempt to demonstrate by means of some random examples how necessary it is to consider fully variability and ontogeny in the investigation of man's evolution and present distinctions. As such this study represents chiefly a compilation and interpretation of some of the writer's old and new observations on primate morphology. A, certain unevenness was unavoidable because some of the facts, made use of, have already been recorded elsewhere and hence can here be mentioned quite briefly, whereas other, new data have to be presented in more detail. Most of the new observations have been obtained by the author with the aid of a grant from the Viking Fund, which is gratefully acknowledged here.