Digit ratio (2D:4D) in Lithuania once and now: testing for sex differences, relations with eye and hair color, and a possible secular change

Coll Antropol. 2007 Sep;31(3):863-8.

Abstract

The second-to-fourth digit ratio (2D:4D) is a sexually dimorphic somatic trait and has been proposed as a biomarker for the organizational, i.e., permanent, effects of prenatal testosterone on the human brain. Accordingly, recent research has related 2D:4D to a variety of sex-dependent, hormonally influenced traits and phenotypes. The geographical variation in typical 2D:4D is marked and presently poorly understood. This study presents the first investigation into the 2D:4D ratio in a Baltic country. A contemporary sample of 109 Lithuanian men and women was compared with data from a historical sample of 100 Lithuanian men and women, collected and published in the 1880s and rediscovered only now. The findings included the following lines of evidence: (i) seen in an international perspective, the average 2D:4D in Lithuania is low; (ii) there was a sex difference in 2D:4D in the expected direction in both samples; (iii) a previously adduced hypothesis of an association of lighter eye and hair color with higher, i.e., more feminized, 2D:4D received no support in both samples; and (iv) the average 2D:4D in the contemporary sample was higher than in the historical sample. In view of a hypothesized increase in 2D:4D in modern populations, owing to increased environmental levels of endocrine disruptors such as xenoestrogens, this latter finding appears to be of particular notice. However, because finger-length measurement methods differed across the samples, it cannot be safely ruled out that the apparent time trend in Lithuanian 2D:4D in truth is an artifact. The puzzling geographical pattern seen in the 2D:4D ratio and the question of possible time trends therein deserve further investigations.

Publication types

  • Comparative Study
  • Historical Article

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Analysis of Variance
  • Biomarkers
  • Body Weights and Measures / history
  • Body Weights and Measures / trends
  • Eye Color / physiology*
  • Female
  • Fingers / anatomy & histology*
  • Hair Color / physiology*
  • History, 19th Century
  • Humans
  • Lithuania
  • Male
  • Middle Aged
  • Observer Variation
  • Reproducibility of Results
  • Sex Characteristics*

Substances

  • Biomarkers