Influence of Change of Sex on the Intensity of Heredity.

Abstract

Of recent years intense interest in the investigation of “sex limited” or “sex linked” inheritance by genetic experimentation has tended to divert attention from some of the phenomena of sex noted by statistical workers many years ago.

Pearson, 1 in studying Francis Galton's data for eye color in human ascendants and descendants, noted that the eye color of the younger generation is more highly correlated with an ascendant or collateral of the same than of the opposite sex, and suggests “that change of sex weakens the intensity of heredity.” Lutz 2 determined the correlations between the eye color of the great grandparents and the great grandchildren and concluded that “every change of sex in the line of ancestry sensibly weakens the intensity of inheritance.”

While the original data are given in multiple categories both Pearson and Lutz used the classical 4-fold table method of determining correlation, dividing the colors for both generations into 2 alternative classes at about the middle of the series of color categories. Since their work was done, papers on contingency 3 and on equivalent probability correlation 4 methods have appeared. It has, therefore, seemed worth while to recalculate these correlations by these 2 methods, and to compare the results with those obtained by Pearson and Lutz with the classical 4-fold method.

The original data were recorded in the categories: 1, Light blue; 2, Blue, dark blue; 3, Grey, blue green; 4, Dark grey, hazel; 5, Light brown; 6, Brown; 7, Dark brown; 8, Very dark brown, black.

In determining the equivalent probability correlation coefficients the same groupings of the original 8 categories were made as were employed by Pearson and Lutz, that is, the series of classes was broken into 2 groups at the line between “grey, blue green” and “dark grey, hazel.”