Page:Popular Science Monthly Volume 84.djvu/147

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THE STUDY OF NATURAL SELECTION
143

associated with hair color and eye color in such a way that the darker classes have the greater recuperative power.[1]

Pearson[2] has also demonstrated correlation of between health and hair color and between health and eye color for data relating to 2,317 boys. Similar results were obtained for girls.

But, on the other hand, there are contradictory evidences. For instance, the conclusion reached by Saunders[3] from his study of pigmentation and susceptibility to diseases in Birmingham school children is that pigmentation is not a factor in selection.

He also finds that relationships between pigmentation and stature and weight, if they exist, are of so delicate a nature that much more refined data than those furnished by the ordinary anthropometric surveys or school medical officer's reports are necessary for their detection.[4]

The discrepancy between his results and those of MacDonald is possibly due to differences in the nature of the populations dealt with. Perhaps, too, data derived from the official examination of school children are less reliable than the hospital returns.

Woodruff has attacked the problem of the relationship of pigmentation to selection from an entirely different, and most important, side.[5] He seeks to determine the relationship between skin color and survival in tropical sunlight. He concludes that the lack of pigmentation is

  1. These conclusions rest solely on the hospital observations. I omit those which involve questions concerning the liability to infection, since they require a knowledge of the distribution of pigmentation in the general population. Such comparisons involve the use of some such basis as the British Association standards or the general anthropometric surveys, which may not be valid for the particular district or social class from which the hospital or asylum inmates are drawn. This was true, for instance, in Strumball's pioneer study, which is highly suggestive rather than conclusive. Again, in attempting to settle the question of differential incidence by an analysis of hospital populations there is the danger of a large personal equation in the appraisal of non-measurable characters. Neither of these difficulties are met when studies of recuperative power are made by a single observer. See also K. Pearson, Biometrika, 8: 39, 1912.
  2. Unpublished results quoted by Saunders, Biometrika, 8: 355, 1912.
  3. A. M. C. Saunders, "Pigmentation in Relation to Selection and to Anthropometric Characters," Biometrika, 8: 354-369, 1912.
  4. Miss Elderton, "On the Relation of Stature and Weight to Pigmentation," Biometrika, 8: 340-353, 1912, concludes from her study of the relationship between hair and eye color and weight and stature: "So far as the material goes we find that types of hair and eye color are not associated to any substantially significant extent with divergencies in height and weight in children between the ages of seven and fourteen, inclusive." It must be noted that Miss Elderton 's problem was in large part undertaken to determine the influence of racial heterogeneity on stature, in its relation to environmental influence.
  5. Chas. E. Woodruff, "The Effect of Tropical Light on White Men," 1905. Also, Science, N. S., 31: 620, 1910.