Page:The American Indian.djvu/387

Rh statures. A similar grouping appears in head measurements, a fine illustration of which is seen in Hrdlicka's data on the Indians of northeastern United States, where we find certain agreements between tribal groups that are contiguous. In short, it appears that as we pass from one social group to another, there is a gradation of somatic characters and that these gradations radiate from centers in much the same way as we noted for culture characters.

Now, if we generalize, it appears that the same leveling causes that unify the internal somatologies of the several social groups also operate to reduce group differences. On logical grounds this leveling will be most marked where the opportunities for sexual contact are greatest, and it follows that these opportunities will be greatest where cultural diffusion is accelerated. It appears, then, that our best lead in the development of a somatic classification is to seek for correlated distinguishing characters in each recognized culture area.

Before proceeding, it may be well to try grouping a few measurements according to these areas. The most accessible are stature and cephalic index, for which we present the