Given that the 2D:4D fixes in utero and the ratio remains stable during development it is regarded as a prenatal marker of testosterone exposure. There is evidence that prenatal testosterone level correlates with the ratio of 2nd to 4th digit length (2D:4D). Testosterone is known to shape neuronal connectivity in the developing brain. Gergely Darnai1*, Enikő Plózer1, Gábor Perlaki1,2,3, Gergely Orsi1,2,3, Szilvia Anett Nagy2, Réka Horváth1, Attila Schwarcz3,4, Norbert Kovács1, Anna Altbäcker1,5 József Janszky1,3 and Zsófia Clemens1,6ġDepartment of Neurology, University of Pécs, Pécs, HungaryģMTA-PTE Clinical Neuroscience MR Research Group, Pécs, HungaryĤDepartment of Neurosurgery, Pécs, HungaryĥInstitute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, HungaryĦNational Institute of Clinical Neuroscience, Budapest, Hungary Our results indicate that prenatal testosterone, as estimated by the 2D:4D ratio has an effect on adult brain morphology in males.

Finger ratio significantly correlated with total cerebral cortex, total cerebellar white matter and total cerebellar cortex in males but not in females.

Freesurfer software suite was used for volumetric segmentation. The length of the 2nd and 4th digits were measured with an electronic vernier caliper while MRI measurements were performed on a Siemens Magnetom Trio Tim (3 T) system. Seventy-five subjects between the ages of 18 and 30 were included in the study. Here we investigated the association between the 2D:4D ratio and several brain subvolumes. '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 estrogen abundance in embryos and the possible consequences for human health.Although there is evidence that the ratio of 2nd to 4th digit length (2D:4D) correlates with prenatal testosterone level, psychological and health traits only a single study has assessed the relationship with brain morphological features. 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. However, not all researchers agree with this theory. 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.

Finger 2d 4d ratio