Page:Popular Science Monthly Volume 51.djvu/33

Rh places of their birth—that is to say, here again physical vigor and the adventurous migratory spirit seemed to stand in close relation to one another.

In times of peace, perhaps the most potent influence of this form of artificial selection bears upon the differences in stature which obtain between different occupations or professions. The physically well developed men seek certain trades or occupations in which their vigor and strength may stand them in good stead: on the other hand, those who are by nature weakly, and coincidently often deficient in stature, are compelled to make shift with some pursuit for which they are fitted. Thus, workers in iron, porters, firemen, policemen are taller, as a class, than the average, because they are of necessity recruited from the more robust portion of the population. In marked contrast to them tailors, shoemakers, and weavers, in an occupation which entails slight demands upon the physical powers, and which is open to all, however weakly they may be, are appreciably shorter than the average. Moreover, certain diseases fall upon this second class in a way which tends still further to lower the average stature among them. Thus, consumption is uncommonly prevalent in these particularly sedentary industrial classes, and it is also more common among tall youths. It seems, therefore, that this disease weeds out, as if by choice, those who within this relatively stunted class rise above its average. As an extreme example of this selective influence exercised in the choice of an occupation we may instance grooms, who as a class are over an inch shorter than the British population as a whole. This is probably because men who are light in build and short in stature find here an opening which is suited to their physique. Their weight may nevertheless be often greater than the stature implies, because of an increase which has taken place late in life.

The final effects of this influence of artificial selection are highly intensified by reason of the fact that, as soon as the choice of occupation is once made, other forces come into play which differentiate still further the stature of the several classes. This is the last of our modifying influences upon racial stature, namely, the effect of habits of life or of the nature of the employment. Thus, the weakly youth who enters a sedentary occupation immediately becomes subjected to unfavorable circumstances as a