'The 2D:4D ratio can't be considered a universal masculinization marker, but it makes sense to use it among other indicators to evaluate the risks of oestrogen abundance in embryos and the possible consequences for human health. These variations can be explained by both genetic factors and specific environmental factors, such as nutrition and stress levels,' explained Marina Butovskaya, Chief Research Fellow at the HSE International Centre of Anthropology. '2D:4D ratio is a sexually dimorphic characteristic, while its degree in total and in sex differences varies from population to population. It is likely that sex and sex hormone levels directly impact the 2D:4D ratio. The lack of correlation between total finger length and 2D:4D ratio does not confirm the alternative explanation of the ratio differences in males and females based on allometry hypothesis. In addition, boys and girls under 13 had about the same finger lengths, while the 2D:4D ratios were already present. But the data analysis showed no evidence of this: sex differences in 2D:4D ratios were present in all nationalities and ages, while finger lengths in men and women varied. It had been assumed that if differences in total finger lengths rather than sexes impact the 2D:4D ratios, then these two indicators will be correlated. To test this hypothesis, the researchers collected data on finger length and 2D:4D ratio from over 7,500 people, including representatives of the three big races, different ages and nationalities they then compared the 2D:4D ratios and finger lengths in these cohorts. Some believe that 2D:4D ratio differences are only due to differences in total finger length and their uneven growth (allometry) in men and women, which is related to specifics in bone or fat tissue development prenatal hormone levels don't play any role. The exposure of interest was the 2D:4D of the women categorized by tertiles, or dichotomized as 1 (index finger longer than the. The 2D:4D was calculated as the ratio of the second and fourth fingers of each hand. However, not all researchers agree with this theory. Digital pictures of the ventral surface of both hands were obtained in the MIREC mothers at the MIREC-CD Plus follow-up study. It is believed that the ratio is due to differences in sex hormones - androgens and oestrogens - particularly during prenatal development. The assumption with 2D:4D ratio is that the ring finger in men is longer than the index finger, while in women, these fingers have equal length or the index finger is longer than the ring one.
The results of the study were published in Scientific Reports. A research team including HSE University scholars refuted this hypothesis by collecting data on finger length from 7,500 people. However, an alternative theory states that men have bigger body parts, including fingers, which impacts the 2D:4D ratio. Our data suggest that prenatal androgen exposure organizes the brain with lasting effects on social behavior.The ratios between the lengths of the second and fourth fingers, known as the 2D:4D ratio, are different in males and females, which is often explained by levels of androgens and oestrogens. The exploratory analysis revealed no link between 2D:4D and responses to the personality trait aggression items or items of anti-social-personality disorder. Furthermore, both factors of sociability (1) liking party and company of friends and (2) isolation intolerance, correlated significantly with the prenatal testosterone marker. These effects were consistent across both hands separately and their mean value. Lower 2D:4D correlated significantly with higher trait sociability, bigger personal social capital, and larger personal social network size. Here, we investigated the association between 2D:4D and the personality trait sociability complemented by personal social capital and personal social network size, in a population-based cohort of 4998 men. The 2D:4D ratio for females was Md 1.000 ( IQR 0.972 and 1.028) for the right hand, Md 1.014 ( IQR 0.982 and 1.038) for the left hand, and Md 1.010 ( IQR 0.981 and 1.031) for the overall hand. Given its role in approach and avoidance behavior, sociability might also be influenced by prenatal sex hormones, but studies are inconclusive so far. How much people enjoy interacting with others is determined by the personality trait sociability. Elevated prenatal exposure to testosterone as indicated by a low second-to-fourth finger length ratio (2D:4D) relates to more aggressive/hostile behavior in men of low 2D:4D, especially in challenging situations. Positive social interactions are crucial for human well-being. Frontiers in Behavioral Neuroscience, 13:246. Lower Digit Ratio (2D:4D) Indicative of Excess Prenatal Androgen Is Associated With Increased Sociability and Greater Social Capital. Buchholz, Verena N Mühle, Christiane Cohort Study on Substance Use Risk Factors Kornhuber, Johannes Lenz, Bernd et al Gmel, Gerhard Mohler-Kuo, Meichun Foster, Simon Marmet, Simon Studer, Joseph (2019).