Sexual Dimorphism in Digit Ratios Derived from Dorsal Digit Length among Adults and Children
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Abstract:
Sexual dimorphism in ventrally measured digit ratios (2D:4D and other) has been related to prenatal sex-hormone levels. In the present series of three studies, we measured all digit lengths (excluding the thumb) on the dorsal, rather than the ventral, side of left and right hands and investigated the sexual dimorphism in digit ratios in three independent samples, two of them comprising adults (Study I, N = 104; Study II, N = 154), and one further, comprising kindergarten children (Study III, N = 64). Results show that men have lower digit-ratio values compared to women in digit ratios that include digit 5 as one of the constituents of the ratio (i.e., the 4D:5D, 3D:5D, and 2D:5D ratios). Boys have lower values compared to girls for the 4D:5D and 3D:5D ratios, and there is a similar trend of sexual dimorphism in the 2D:5D ratio. Thus, based on the evidence from dorsally measured digit ratios, the present findings from three samples are consistent with the idea that early sex-hormonal effects might be stronger for digit ratios involving digit 5, as compared to the classic, and frequently studied, ventrally measured 2D:4D ratio.Keywords:
Digit ratio
Numerical digit
Sexual dimorphism
Sex characteristics
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[Objective]To study the digit ratio of Bouyei ethnic group in Guizhou,ananlyze the mean values of left and right hands of different sexes.[Methods]Physique measurements were used to study the digit ratios(2D︰3D,2D︰4D,2D︰5D,3D︰4D,3D︰5D,4D︰5D)of left and right hands of 312 individuals(153 males,159 females)of the Bouyei.[Results]The mean values of digit ratios presented a trend as:2D︰3D2D︰4D3D︰4D2D︰5D4D︰5D3D︰5D.Significant differences of 2D︰3D,2D︰4D of left and right hands were found between males and females(P0.05 or P0.01).Females had higher mean values than males.[Conclusion]There is sexual difference in digit ratio and an obvious sexual difference in 2D︰4D.
Digit ratio
Numerical digit
Sexual difference
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The 2nd to 4th digit ratio (2D:4D) is a sexually dimorphic biometric marker, related to prenatal estrogen and testosterone levels in-utero and determined genetically by HOX genes. The prenatal effects of testosterone on development of brain hemispheres are considered as a key factor in etiology of left-handedness. Besides sexual dimorphism, 2D:4D ratio shows significant ethnic and population differences. The aim of the present study is to provide an authentic database on right and left 2D:4D ratios in two different ethnic groups of a particular age and sex, and study its correlation with handedness and sexual dimorphism. The study was conducted on 300 Haryanvi Brahmins (150 each of either sex) and 300 Kashmiri Pandits (150 each of either sex) of the age group of 18 years and above. The values for 2D:4D ratio was calculated for both the hands. Hand preference was established according to Edinburgh Inventory and five hand-preference determination groups were constituted after calculation of laterality score. The results were tabulated and subjected to statistical analysis. Mean values for 2D:4D ratio in both the ethnic groups were found to be higher in females than in males. When the values of 2D:4D ratio were assessed by sex, the values were found to be statistically significant (p<0.001). When relationship between laterality score (indicator of hand preference) and 2D:4D were examined, the values were found to be significant only in Haryanvi Brahmins (males) on the right side.
Digit ratio
Sexual dimorphism
Kashmiri
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Digit ratio
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Sexual differences in the index to ring finger length ratio (2D:4D ratio) have been observed since more than 150 years ago, and they are already present in the foetus. Homeobox genes, which also control the differentiation of testes and ovaries, are involved in finger conformation, which is subjected to the influence of testosterone and estrogen levels. In general, women show larger 2D:4D digit ratios, although differences between sexes are subjected to ethnic variations. This study was performed in order to analyse the absolute values of several digit ratios (2D:4D; 4D:3D; 2D:3D) among 164 young adults of Tenerife (101 women). Finger lengths were directly measured dorsally using a calliper with an accuracy level of 0.01 mm. Dorsal digit lengths were defined as the distance between the fingertip and the dorsal base of the proximal phalanx, in a position in which fingers and palms formed an angle of 90o. We found that 2D:4D of both hands (for instance, women=0.9631 ± 0.02647; men= 0.9535 ± 0.02507 for the left 2D:4D ratios), the left 2D:3D (0.9063 ± 0.02216 in women; 0.8980 ± 0.01931 among men) and the right 4D:3D ratios (0.9377 ± 0.03625 among women vs 0.9471 ± 0.02138 among men) were significantly different among men and women. The magnitude of the difference among sexes is similar to that reported for other populations, and they allow for the elaboration of a discriminant function with an accuracy of 60.4%, that reaches 86% if stature is also included. We applied this discriminant function to a test group composed of 36 randomly selected women and 24 men, obtaining an accuracy of 58.33% and 81.67%, respectively.
Digit ratio
Numerical digit
Ring finger
Phalanx
Dermatoglyphics
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Abstract Objective 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. Methods 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). Results 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. Conclusions 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.
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Studies on many populations have shown that the length of the second finger (2D) compared to the fourth (4D), expressed as the finger length ratio (2D:4D), might be characteristic for sexual dimorphism. It was also found that the values of 2D:4D differ significantly between examined populations. It is thought that the value of 2D:4D is determined in early foetal life under the influence of genetic factors and the strong influence of sex hormones. It has been proven that the values of 2D:4D are related to, for instance, sexual orientation, and artistic and sporting ability. Recently, increasing interest in the clinical signifi- cance of finger length ratio in the diagnosis of somatic and mental disorders has been observed. For example, it was found that values of 2D:4D in individuals suffering from congenital adrenal hyperplasia or autism were significantly lower compared to healthy subjects. The aim of the study was to determine sexual dimor- phism in finger length ratio among representatives of the Polish population.The study group comprised 115 people (57 females and 58 males). Anthropometric meas- urements were taken from the second and fourth finger of the right and left hands - from the point of dactylion (da) to pseudophalangion (pph) using analogue callipers. We calculated the significance of differences in 2D:4D between males and females separately for the right and left hands.In both hands mean 2D:4D values were lower in males than in females. The difference in the right hand reached the statistical significance level with p < 0.05.Among the subjects from the examined population the 2D:4D ratio shows trends characteristic for sexual dimorphism.
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Human 2D : 4D ratios (measures of the relative lengths of index and ring fingers) attract considerable research interest because they exhibit sexual dimorphism and are associated with various morphological, physiological and behavioural traits as well as sporting abilities and medical conditions. In an attempt to identify potential confounding factors in such studies, we have examined how relative and absolute digit lengths vary with gender and tested whether they are influenced by age, right-left asymmetry and hand preference. Participants between 4 and 60 years of age were recruited from local educational sites. Hand photocopies and calliper measurement were used to obtain digit lengths. We employed linear regression analysis to examine the growth trajectories of individual digits, analyses of variance to isolate main and interaction effects of age, gender and hand preference, and paired t-tests to identify lateral asymmetries. Both digits exhibited biphasic growth with an early growth phase followed by a stable length phase. Digits in females attained their maximum length about 2.2 years (dextral subjects) or 5.1 years (sinistral subjects) earlier than those in males. Sexual dimorphism in 2D : 4D ratios was apparent by 4 years of age and age changes in ratios depended on gender, side and hand preference. Relative and absolute lengths displayed age, gender, hand-preference and age x gender interaction effects. Lengths tended to be greater in females in younger subjects and greater in males in older subjects. Ratios tended to be greater in sinistral subjects. In dextral subjects, significant lateral asymmetries in 2D lengths were seen at all ages but asymmetries in males and 4D lengths seemed to be age-dependent. We conclude that age, lateral asymmetry and hand preference are potential confounding factors and that future study designs should take account of these as well as other known confounders such as ethnicity, birth order, menstrual cycle phase and sexual preference.
Sexual dimorphism
Digit ratio
Fluctuating asymmetry
Numerical digit
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Sexual dimorphism in ventrally measured digit ratios (2D:4D and other) has been related to prenatal sex-hormone levels. In the present series of three studies, we measured all digit lengths (excluding the thumb) on the dorsal, rather than the ventral, side of left and right hands and investigated the sexual dimorphism in digit ratios in three independent samples, two of them comprising adults (Study I, N = 104; Study II, N = 154), and one further, comprising kindergarten children (Study III, N = 64). Results show that men have lower digit-ratio values compared to women in digit ratios that include digit 5 as one of the constituents of the ratio (i.e., the 4D:5D, 3D:5D, and 2D:5D ratios). Boys have lower values compared to girls for the 4D:5D and 3D:5D ratios, and there is a similar trend of sexual dimorphism in the 2D:5D ratio. Thus, based on the evidence from dorsally measured digit ratios, the present findings from three samples are consistent with the idea that early sex-hormonal effects might be stronger for digit ratios involving digit 5, as compared to the classic, and frequently studied, ventrally measured 2D:4D ratio.
Digit ratio
Numerical digit
Sexual dimorphism
Sex characteristics
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Citations (18)
The digit ratio, or the relative lengths, of the 2nd and 4th digits (2D : 4D) shows a sex difference, with males tending to have lower values in comparison with females. This sex differences arises early in the fetus and may result from the effects of prenatal testosterone and estrogen on the relative growth rate of the 2nd and 4th digits. This study aimed to estimate finger lengths and the 2D : 4D ratios for the first time in Saudi Arabian subjects using direct and indirect measurements, and to evaluate the correlations between both indirect and direct 2D : 4D with adult testosterone and various sexually dimorphic physical traits. The results revealed the following: (i) mean 2D : 4D in Saudi Arabian samples varied from 0.96 to 0.99; (ii) mean 2D : 4D was lower for indirect compared to direct 2D : 4D; (iii) sex differences in indirect 2D : 4D were higher than in direct 2D : 4D measurements; (iv) there were no significant correlations between indirect or direct 2D : 4D and testosterone level; (v) there were four significant correlations between direct 2D : 4D and body size traits but no significant correlations between indirect 2D : 4D and body size.
Numerical digit
Digit ratio
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Numerous studies have demonstrated sexual dimorphism in 2D:4D digit ratio. Shall be regarded that the value of the 2D:4D ratio is determined in fetal life by the action of hormones. The aim of the study was to evaluate asymmetry and sexual dimorphism in 2D:4D digit ratio.The study was conducted on a group of 115 women and 46 men, aged 19–25 years. Individuals, which were included in the study, are students of two universities in Cracow – Academy of Physical Education and the Jagiellonian University. The measurement of the length the fingers II and IV both hands was made in each person and the value of digit ratio was calculated for all obtained data.The women had the higher value of the index 2D:4D in both hands, compared with men covered by the survey. In males it was demonstrated higher average value of the length of the finger IV than the finger II.
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