John T Manning1, Bernhard Fink2,3. 1. Applied Sports, Technology, Exercise, and Medicine (A-STEM), Swansea University, Swansea, United Kingdom, University of Swansea. 2. Department of Behavioral Ecology, University of Goettingen, Germany. 3. Hanse-Wissenschaftskolleg, Institute for Advanced Study, Delmenhorst, Germany.
Abstract
OBJECTIVE: Sex differences are often reported in digit lengths and digit ratio (2D:4D). However, the ontogeny of these sex differences and their interrelationships are less well known. METHODS: We considered sex differences in the lengths of the 2nd (2D) and 4th (4D) digit and 2D:4D in children aged 2 to 18 years (Sample I, n = 680) and adults aged 18 to 30 years (Sample II, n = 89,246). Digit length was determined by direct experimenter-measurement (Sample I) and direct self-measurement (Sample II). The data were tested with two-factor ANOVA's (sex and year-group). RESULTS: In both samples, there were significant main effects of sex and year-group, and a significant interaction effect on digit length. Digit length was positively related to age in both samples. Boys had longer digits than girls but only after 13 years. Men had longer digits than women and the dimorphism increased from 18 to 30 years. There were significant sex differences in 2D:4D (males < females), but no significant effect of age and no interaction effect of age and sex on 2D:4D in children or adults. CONCLUSIONS: Between 2 and 30 years, the lengths and the sexual dimorphisms of 2D and 4D are dependent on age. In contrast, 2D:4D is not age-dependent. We discuss our findings in the context of the ontogeny of digits and in the light of recent claims on the presence of static allometry in 2D and 4D lengths.
OBJECTIVE: Sex differences are often reported in digit lengths and digit ratio (2D:4D). However, the ontogeny of these sex differences and their interrelationships are less well known. METHODS: We considered sex differences in the lengths of the 2nd (2D) and 4th (4D) digit and 2D:4D in children aged 2 to 18 years (Sample I, n = 680) and adults aged 18 to 30 years (Sample II, n = 89,246). Digit length was determined by direct experimenter-measurement (Sample I) and direct self-measurement (Sample II). The data were tested with two-factor ANOVA's (sex and year-group). RESULTS: In both samples, there were significant main effects of sex and year-group, and a significant interaction effect on digit length. Digit length was positively related to age in both samples. Boys had longer digits than girls but only after 13 years. Men had longer digits than women and the dimorphism increased from 18 to 30 years. There were significant sex differences in 2D:4D (males < females), but no significant effect of age and no interaction effect of age and sex on 2D:4D in children or adults. CONCLUSIONS: Between 2 and 30 years, the lengths and the sexual dimorphisms of 2D and 4D are dependent on age. In contrast, 2D:4D is not age-dependent. We discuss our findings in the context of the ontogeny of digits and in the light of recent claims on the presence of static allometry in 2D and 4D lengths.
Authors: Ann Mary Alex; Tom Ruvio; Kai Xia; Shaili C Jha; Jessica B Girault; Li Wang; Gang Li; Dinggang Shen; Emil Cornea; Martin A Styner; John H Gilmore; Rebecca C Knickmeyer Journal: Cereb Cortex Date: 2022-07-21 Impact factor: 4.861