The relation between total finger ridge-count and variability of counts from finger: genetic implications of racial variation.

The measure of ridge-count diversity, S/square root 10, was computed for a sample of American Whites, American Blacks and African Blacks, and the regression of S/square root 10 on total ridge-count was determined for each group. The shapes of the regression lines differed considerably. The American White curve was very similar to that obtained by Holt in an English sample, while the two Negro curves generally showed lower lower S/square root 10 values for ridge-counts over 80. The American Negro curve was found to behave like a mixture of the White and African Negro curve to a degree approximating to the fraction of White genes in their gene pool. Holt's parent-child data are used to construct a simple test of the hypothesis that that S/square root 10 reflects zygosity in total ridge-count genotypes. The preliminary results support this hypothesis.