Digit ratios among the modern population of the Canary Islands

ABSTRACT

Sexual differences in the index to ring finger length ratio (2D4D ratio) have been observed since more than 150 years ago, and they are already present in the foetus. Homeobox genes, which also control the differentiation of testes and ovaries, are involved in finger conformation, which is subjected to the influence of testosterone and estrogen levels. In general, women show larger 2D4D digit ratios, although differences between sexes are subjected to ethnic variations. This study was performed in order to analyse the absolute values of several digit ratios (2D4D; 4D3D; 2D3D) among 164 young adults of Tenerife (101 women). Finger lengths were directly measured dorsally using a calliper with an accuracy level of 0.01 mm. Dorsal digit lengths were defined as the distance between the fingertip and the dorsal base of the proximal phalanx, in a position in which fingers and palms formed an angle of 90º. We found that 2D4D of both hands (for instance, women=0.9631 ± 0.02647; men= 0.9535 ± 0.02507 for the left 2D4D ratios), the left 2D3D (0.9063 ± 0.02216 in women; 0.8980 ± 0.01931 among men) and the right 4D3D ratios (0.9377 ± 0.03625 among women vs 0.9471 ± 0.02138 among men) were significantly different among men and women. The magnitude of the difference among sexes is similar to that reported for other populations, and they allow for the elaboration of a discriminant function with an accuracy of 60.4%, that reaches 86% if stature is also included. We applied this discriminant function to a test group composed of 36 randomly selected women and 24 men, obtaining an accuracy of 58.33% and 81.67%, respectively

RESUMEN

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