Applied Sports, Technology, Exercise, and Medicine (A-STEM), Swansea University, Swansea, United Kingdom, University of Swansea.
Department of Behavioral Ecology, University of Goettingen, Germany.
Am J Hum Biol. 2018 Jul;30(4):e23138. doi: 10.1002/ajhb.23138.
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.
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).
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.
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.
手指长度和指长比（2D:4D）常存在性别差异。然而，这些性别差异的发生发展及其相互关系还不太清楚。
我们考虑了 2 至 18 岁儿童（样本 I，n=680）和 18 至 30 岁成人（样本 II，n=89246）中 2 指（2D）和 4 指（4D）长度以及 2D:4D 的性别差异。通过直接实验者测量（样本 I）和直接自我测量（样本 II）确定手指长度。数据用双因素方差分析（性别和年龄组）进行检验。
在两个样本中，手指长度存在显著的性别和年龄组主效应，以及显著的性别和年龄组交互效应。在两个样本中，手指长度均与年龄呈正相关。男孩的手指比女孩长，但仅在 13 岁后。男性的手指比女性长，且这种二态性从 18 岁到 30 岁逐渐增加。2D:4D 存在显著的性别差异（男性<女性），但儿童和成人中年龄无显著影响，且年龄与性别的交互作用也无显著影响。
在 2 至 30 岁之间，2D 和 4D 的长度及其性别二态性依赖于年龄。相比之下，2D:4D 与年龄无关。我们在手指发生发展的背景下讨论了我们的发现，并根据最近关于 2D 和 4D 长度存在静态比例的说法进行了讨论。
