THE study of genetic theory and of the processes of microevolution with human material is very difficult, and little actual work has been done. Fortunately, such a study appeared in this journal (Kraus and White 1956) while the present investigation was under way, thus obviating the need for much preface here. Let us simply make two main points. first is the influence of culture on breeding behavior, through different mating systems, different sizes or densities, different opportunities for gene exchange, and so forth (see especially Kluckhohn and Griffiths 1950). This should be a differential of some effect in the case of man, and it compels a relationship between cultural and physical anthropology which has to a great extent been neglected, as Kraus and White point out. For example, The results of this neglect are twofold: first, the phenotypic and genotypic frequencies are not necessarily representative of the designated population, and second, t -called (or nation or tribe, etc.) is not necessarily a biologicalhbreeding unit, since only a careful study of social institutions, particularly such social groups as the clan, the local community, and the band, can possibly determine the true breeding population (Kraus and White 1956:1019). But blame can be shared by both physical and cultural anthropologists, for new demands are now placed upon the usual field procedures, since the quantification of data is a prerequisite. cultural anthropologist must not only describe, he must count (Kraus and White 1956:1018). second is the fact that theorems of genetics, and applications of them, relate very largely, though by no means entirely, to single genepair traits. However, traits of continuous variation (such as underlie the familiar anthropological measurements of form) are doubtless determined by several loci, and may be polygenic in the proper sense; hence much less can be said about them (but see Mather 1949; Darlington and Mather 1950; Reeve and Waddington 1952). Yet these traits constitute a whole field of human variation in size and shape, furthermore involving modification by environment as well as the relationship and differentiation of populations-in short, all the processes of micro-evolution. It should also be noted that this normal morphology is traditionally the central field not only of physical anthropology but of zoology and paleontology as well. Snyder's remarks (1950:163) on this subject are especially pertinent: