Study in Namibia points out that males & females with a low 2D:4D digit ratio tend to get married at an early age:

The second to fourth digit ratio (2D:4D) is used as a potential marker for prenatal androgen exposure. It is associated with many behavioral and biological variables, including fertility and sexual behavior. However, direct association between 2D:4D and reproductive success—in populations where no contraceptives are used—has not been investigated. Here, we present a study conducted among the semi-nomad Himba population living in northern Namibia. 2D:4D ratios were calculated for a sample of this population (N = 99; 60 women, 39 men), and the results were correlated with age, marital status, age at first marriage, number of children, and number of marriages. As found in the majority of previous studies, males had lower 2D:4D ratios than females. The 2D:4D ratio did not correlate with number of children. Females and males with a more masculine 2D:4D were married earlier and were more likely to have a husband or wife. We suggest that mating preferences for females with masculine 2D:4D are related to masculinity of phenotypic and personality traits of such women, which are beneficial in harsh environmental conditions and/or higher facial masculinity, which influences the perceived age of an individual. At the same time, masculine (physically strong, dominant, and hardworking) males might gather resources necessary to marry their first wife earlier.

NOTICE: 2D:4D digit ratio is known to correlate with many aspects of marriage/relationships, including e.g. the age of the partner, the number of partners, the offspring & the wearing of wedding rings.

On october 9 (2012) Manning presented the very first 2D:4D digit ratio study in Klinefelter syndrome (XXY).

The results describe how Klinefelter syndrome is typically featured with a high 2D:4D digit ratio + short fingers.


The ratio of second to fourth digit length (2D:4D) is a correlate of prenatal testosterone. High 2D:4D is associated with low prenatal testosterone, and reduced sensitivity to testosterone. Klinefelter’s syndrome (KS; 47 XXY) affects the endocrine system, such that low testosterone levels are found in KS foetuses, new-borns and adults. To date, there are no published data regarding the pattern of 2D:4D in KS males. Here we consider 2D:4D in KS individuals (n = 51), their relatives (16 fathers and 15 mothers) and an unaffected control sample of 153 men and 153 women. Adult KS individuals were taller than their fathers and had shorter fingers than fathers and male controls. Compared with fathers, male controls and mothers, KS males had shorter fingers relative to height. With regard to 2D:4D, KS individuals had higher 2D:4D than fathers (right and left hands), male controls (right and left hands) and mothers (left hands). Among KS males older than 13 years there were 34 individuals currently prescribed testosterone and nine not prescribed. In comparison to the former, the latter individuals had higher right 2D:4D and higher right–left 2D:4D. We conclude that KS males have mean 2D:4D values similar to those found in female population norms. In addition, testosterone supplementation in KS males may be most common for individuals with low right 2D:4D.


  • 2D:4D;
  • azoospermia;
  • digit ratio;
  • Klinefelter’s syndrome;
  • prenatal testosterone;
  • testosterone sensitivity

After various digit ratio studies found conflicting results related to Extraversion & sensation seeking (most pointed into the direction of a negative correlation), a new Dutch 2012 study suggest that other finger lengths require to be taken into account in order to find more clear results!

 The (unpublished) results from a female only suggest that low 2D:4D digit ratio + long pinky finger are much more often found in the hands of ‘extroverts’ (8 out of 40 hands = 20%), while this combination is rarely seen in the hands of ‘introverts (0 out of 28 hands = 0%).

Additionally, a high 2D:4D digit ratio with short pinky finger is much more common in the hands of ‘introverts’ (5 out 28 hands = 18%),  compared to the hands of ‘extroverts’  (3 out of 40 hands = 7.5%).

More details:

13 Hand signs for Extraversion / Introversion