Page:Popular Science Monthly Volume 80.djvu/487

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important ones are forearm and span in Pearson's investigation.[1] For the direct[2] comparisons the resemblance is quite material, amounting to about + .200. Cross correlations are in general somewhat lower. Possibly the assortative mating is primarily for stature, while the resemblance for forearm and span arise merely because these are closely associated with stature. This point is not as certain, however, and deserves more attention.

For forty-eight families of East European (Russian) Jews living in New York City, Boas[3] found an assortative mating for cephalic index (relative head breadth) of r = + .15 ± .10.

Lutz's interesting data on the inheritance of the method of clasping the hands[4] show a positive sign in the correlation between the two parents, but it is so very small that no significance is to be attached to it.

3. Complexion and Hair and Eye Color

Complexion and hair and eye color are conspicuous with stature in the popular superstition of "the charm of disparity" in human matings.

The calculation of the intensity of relationship in the case of a character which like eye color is not quantitatively measurable presents considerable difficulties, and the results vary with the method employed. From an analysis of Francis Galton's "Family Records," Pearson[5] has deduced the following values:[6]

Correlation by four-fold method + .10 ± .04
Mean contingency + .31
Mean square contingency + .26 ± .03

    numbers are too few to calculate the contingencies on the basis of his grouping, and the classes are too indefinite for satisfactory combination.

  1. Length of forearm is the distance from the bony projection of the elbow, with the arm folded as much as possible, to the tip of the middle finger. The span is the greatest possible distance between the tips of the middle fingers of the outstretched hands.
  2. By direct correlation we mean the degrees of resemblance calculated for the same organs in husband and wife, by cross correlation those in which the characters are different. The entries in the table makes this quite clear.
  3. Boas, F., "Heredity in Head Form," Amer. Anthrop., N. S., Vol. 5, p. 532, 1903.
  4. Lutz, F. E., Amer. Nat., Vol. 42, pp. 195-196, 1908.
  5. Pearson, K., Phil. Trans. Roy. Soc. Lond., A, Vol. 195, pp. 113, 149-150, 1900; "Grammar of Science," 2d ed., pp. 431-437, 1900; Biometrika, Vol. 5, pp. 475, 1907.
  6. Yule (Journ. Anth. Inst., Vol. 36, p. 359, 1906) has drawn these results into question on the supposition that they may be due to a personal equation or bias of the observer, which might lead him to classify both members of a pair alike. His criticism is well answered by Pearson (Biometrika, Vol. 5, p. 475, 1907).