Sexual dimorphism in the prenatal digit ratio (2D:4D). (original) (raw)
Related papers
sexual Dimorphism in Digit ratios Derived from Dorsal Digit length among adults and children
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 (2D:4D) in newborns: Influences of prenatal testosterone and maternal environment
Early Human Development, 2013
Introduction: The 2D:4D digit ratio is sexually-dimorphic, probably due to testosterone action through the perinatal period. We characterize the 2D:4D ratio in newborn (NB) infants, in between the pre-and postnatal surges of testosterone, and relate it to the mother's 2D:4D and to testosterone levels in the amniotic fluid (AF). Subjects and methods: Testosterone was assayed in samples of maternal plasma and AF collected at amniocentesis. Shortly after birth, 106 NBs and their mothers were measured for 2D:4D ratio. Results: NB males had lower mean 2D:4D ratios than females but this dimorphism was significant only for the left hand (males: 0.927; females: 0.950; p =0.004). Mothers who had sons had lower 2D:4D ratios than those who had daughters and the mother's 2D:4D were higher than those of NBs regardless of sex. Both hands of NB females were negatively correlated with AF testosterone and positively correlated with the mother's 2D:4D, but males showed no significant associations. Maternal plasma testosterone also showed a negative weak correlation with NB's digit ratio in both sexes. Conclusions: Sexual dimorphism at birth was only significant for the left hand, in contrast with reports of greater right hand dimorphism, suggesting that postnatal testosterone is determinant for 2D:4D stabilization. The lower 2D:4D ratios in mothers who had sons support claims that hormone levels in parents are influential for determining their children's sex. NB female's digit ratio, but not males', was associated to the level of AF testosterone. The mother's 2D:4D ratios were positively correlated with their daughters' 2D:4D, but the same was not observed for male NBs, suggesting that prenatal testosterone levels in male fetus lead their 2D:4D ratios to stray from their mothers' with high individual variability.
No sexual dimorphism in human prenatal metacarpal ratios
Early Human Development, 2014
Background: Ratios of digit lengths are studied intensively as markers of prenatal sex hormone levels. Aim: Study sexual dimorphism in ratios of metacarpals, which received less attention. Methods: We studied six metacarpal ratios in deceased human fetuses of ages 10 to 42 weeks. Results and conclusion: We found no indication of a sexual dimorphism at this early stage of development.
Sexual Dimorphism in Humans-During Foetal Development, In Adult Metabolism
2015
According to recent findings both X and Y chromosome could have evolved from autosomal ancestors about 300 million years ago. In humans, the typical male has a diploid karyotype of 46 chromosomes i.e. 22 pairs of autosomes and XY pair of gonosomes(46,XY).A standard female karyotype is 46 XX.Thus humans are dimorphic: there is one type of humans who are males and the other type is female. The basis of sexual dimorphism in mammals derives from evolution of sex chromosomes (1). Probably a failure occurred in homologous recombination which resulted in the formation of a small area that was not identical to the two participating chromosomes. The presence or absence of this region coincided with a different pattern of development that altered androgen activity resulting in a sex determining role. In all living mammalians to day, this area in Y chromosome appears to retain the regulatory function and therefore described as the sex Determining Region of Y chromosome or SRY gene(2).But sexua...
Human Biology Review, 2023
The second-to-fourth digit (2D:4D) ratio is a sexually dimorphic trait, with men having lower ratios than women, indicating relatively higher prenatal testosterone exposure compared to oestrogen. The 2D:4D ratio is fixed in intrauterine conditions that are affected by foetal sex steroids (testosterone and oestrogen) and an indirect method to determine intrauterine sex hormone levels that significantly correlate with somatic features, behavioural traits, fertility measures, reproductive characteristics, and predisposition to certain chronic diseases. Researchers discovered that a more masculine (low 2D<4D) digit ratio and a more feminine (high; 2D>4D) digit ratio are manifestations of increased prenatal testosterone and oestrogen exposure, respectively. Furthermore, digit ratio (2D:4D) values are widely used to predict reproductive capacity and success, fertility measures, natural menopause, and age at menarche, which varies between populations. The current review paper attempted to discuss sexual dimorphism in 2D:4D ratios, as well as its potential association and utility in evaluating certain reproductive characteristics and behavioural traits in populations. Methodological comparisons, benefits and drawbacks of determining the 2D:4D for studying the effect of prenatal sex steroids are also highlighted.
The ratio of length between the second (index) and fourth (ring) fingers (digit ratio or 2D:4D) is frequently employed as a retrospective marker of prenatal sex hormone exposure. Lutchmaya et al. (2004) reported that the ratio of testosterone (T) to estradiol (E) present in second trimester amniotic fluid was negatively correlated with digit ratios for the right hand (but not the left hand) in a sample of 29 children at 2-year follow-up. This observation is frequently cited as evidence for the measure’s validity but has not been replicated. We therefore present the findings of another study of amniotic T and E that did not find evidence for these effects at 4½-year follow-up. The confidence intervals were large, the direction of correlations observed was generally erratic, and the overall findings therefore question the premise that second trimester sex hormones affect the development of digit length ratios in humans.
Journal of Developmental Origins of Health and Disease, 2021
The ratio of length between the second (index) and fourth (ring) fingers (digit ratio or 2D:4D) is frequently employed as a retrospective marker of prenatal sex hormone exposure. Lutchmaya et al. (2004) reported that the ratio of testosterone (T) to estradiol (E) present in second trimester amniotic fluid was negatively correlated with digit ratios for the right hand (but not the left hand) in a sample of 29 children at 2-year follow-up. This observation is frequently cited as evidence for the measure's validity but has not been replicated. We therefore present the findings of another study of amniotic T and E that did not find evidence for these effects at 4½-year follow-up. The confidence intervals were large, the direction of correlations observed was generally erratic, and the overall findings therefore question the premise that second trimester sex hormones affect the development of digit length ratios in humans.
Establishing Sexual Dimorphism in Human
2006
Sexual dimorphism, i.e. the distinct recognition of only two sexes per species, is the phenotypic expression of a multistage procedure at chromosomal, gonadal, hormonal and behavioral level. Chromosomal – genetic sexual dimorphism refers to the presence of two identical (XX) or two different (XY) gonosomes in females and males, respectively. This is due to the distinct content of the X and Y-chromosomes in both genes and regulatory sequences, SRY being the key regulator. Hormones (AMH, testosterone, Insl3) secreted by the foetal testis (gonadal sexual dimorphism), impede Müller duct development, masculinize Wolff duct derivatives and are involved in testicular descent (hormonal sexual dimorphism). Steroid hormone receptors detected in the nervous system, link androgens with behavioral sexual dimorphism. Furthermore, sex chromosome genes directly affect brain sexual dimorphism and this may precede gonadal differentiation
Establishing sexual dimorphism in humans
Collegium antropologicum, 2006
Sexual dimorphism, i.e. the distinct recognition of only two sexes per species, is the phenotypic expression of a multi-stage procedure at chromosomal, gonadal, hormonal and behavioral level. Chromosomal--genetic sexual dimorphism refers to the presence of two identical (XX) or two different (XY) gonosomes in females and males, respectively. This is due to the distinct content of the X and Y-chromosomes in both genes and regulatory sequences, SRY being the key regulator Hormones (AMH, testosterone, Insl3) secreted by the foetal testis (gonadal sexual dimorphism), impede Müller duct development, masculinize Wolff duct derivatives and are involved in testicular descent (hormonal sexual dimorphism). Steroid hormone receptors detected in the nervous system, link androgens with behavioral sexual dimorphism. Furthermore, sex chromosome genes directly affect brain sexual dimorphism and this may precede gonadal differentiation.