The development of sex differences in digital formula from infancy in the Fels Longitudinal Study

Department of Anthropology, Harvard University, Peabody Museum, 11 Divinity Avenue, Cambridge, MA 02138, USA.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.29). 08/2005; 272(1571):1473-9. DOI: 10.1098/rspb.2005.3100
Source: PubMed

ABSTRACT Relative finger lengths, especially the second-to-fourth finger length ratio, have been proposed as useful markers for prenatal testosterone action. This claim partly depends on an association of relative finger lengths in adults with related sex differences in children and infants. This paper reports the results of a study using serial radiographs to test for both sex differences in the fingers of infants and children and for a relationship between sex differences in the children and infant finger and adult finger length ratios. This is the first study using long-term serial data to evaluate the validity of finger length ratios as markers. We found not only that sex differences in finger length ratios arise prior to puberty, but that sex differences in the fingers of children are highly correlated with adult finger length ratios. Our results strongly encourage the further use of finger length ratios as markers of perinatal testosterone action.

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Available from: Ellen Demerath, May 07, 2015
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    • "The small but reliable association between relative finger length and prenatal androgen/estrogen balance makes the digit ratio a viable biomarker for early exposure to sex hormones. The gold standard for digit ratio measurement is based on bone length estimation from X-rays, CT scans, or similar methods (e.g., McIntyre et al. 2005); however, most studies in humans measure digit ratios indirectly on the skin surface, either with a caliper or from hand scans or photocopies. While indirect methods are considerably more practical, they increase the measurement error associated with 2D:4D estimation and further weaken the correlation with early hormonal exposure. "
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    ABSTRACT: Sex differences in attachment are absent during infancy and early childhood, emerge in middle childhood with self-reports and doll-play tasks, and persist into adulthood, when they are most reliably detected in romantic attachment styles. In our previous work, we hypothesized that sex differences in attachment develop under the influence of adrenal androgens during the transition form early to middle childhood, following activation of hormone-sensitive neural pathways organized by prenatal and early postnatal exposure to sex hormones. In this study we tested the association between the right-hand 2D:4D digit ratio (a marker of early exposure to androgens and estrogen) and sexually differentiated dimensions of attachment in middle childhood assessed with the Coping Strategies Questionnaire (CSQ). In a sample of 285 Italian children aged 8–10 years, females scored lower in avoidance and higher in preoccupation, while no significant sex differences were observed in felt security. Consistent with our predictions, higher (feminized) digit ratios were significantly associated with lower avoidance and higher preoccupation scores in both males and females. In contrast, there was no significant association between digit ratio and felt security in either sex. These results corroborate the hypothesis that sex differences in attachment reflect the activation of sexually differentiated pathways organized in early development, and for the first time implicate sex hormones in the development of individual differences in attachment styles.
    05/2015; DOI:10.1007/s40750-015-0027-3
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    • "Third, the r2D:4D digit ratio has been shown to be a proxy, albeit not very precise, for prenatal androgen exposure (Hell and P ¨ aßler, 2011; Lippa, 2003). Also, one should bear in mind that factors other than androgens affect digit growth (McIntyre et al., 2005; Voracek, Manning, and Dressler, 2007). Furthermore, the availability of androgens in the body's extremities when a growth spurt occurs in the fourth digit cannot be considered anything but roughly associated with androgen levels inside the nervous system during critical periods of fetal development (McIntyre, 2006; Talarovicová , Krsková , and Blazeková , 2009). "
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    ABSTRACT: Evolutionary neuroandrogenic (ENA) theory asserts that criminality is a crude form of competitive behavior over resources, status, and mating opportunities. Theoretically, males have been selected for resource acquisitiveness as a result of female preferences for mates who are successful at resource provisioning. ENA theory also asserts that brain exposure to both prenatal and postpubertal androgens (particularly testosterone) promotes all forms of competitiveness, including those that victimize others. The present study was undertaken to test ENA theory by correlating 14 self-reported measures of offending with a biomarker for fetal testosterone exposure based on the ratio of the 2nd and 4th digits of the right hand (r2D:4D), in a nonrepresentative sample of 445. Both Spearman correlations and negative binomial regressions produced results that largely supported the hypothesized connection between offending and high prenatal androgen exposure, even when findings were analyzed separately by sex. Also, offending was significantly associated with r2D:4D for both males and females. Overall, this study supports the view that exposing the brain to high levels of testosterone and other androgens prenatally elevates the probability of offending later in life.
    Criminology 12/2014; 53(1). DOI:10.1111/1745-9125.12056 · 2.47 Impact Factor
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    • "Digit ratio in humans is established during the first trimester of development (Malas et al. 2006), coinciding with a period of high testosterone production in males (Abramovich 1974). Furthermore, it appears to remain stable across the lifespan (McIntyre et al. 2005). Until recently, evidence for Manning's biomarker hypothesis had come entirely from correlational studies (McIntyre 2006). "
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    ABSTRACT: Men and women differ statistically in the relative lengths of their index and ring fingers; and the ratio of these lengths has been used as a biomarker for prenatal testosterone. The ratio has been correlated with a wide range of traits and conditions including prostate cancer, obesity, autism, ADHD, and sexual orientation. In a genome-wide association study of 979 healthy adults, we find that digit ratio is strongly associated with variation upstream of SMOC1 (rs4902759: P = 1.41 × 10(-8)) and a meta-analysis of this and an independent study shows a probability of P = 1.5 × 10(-11). The protein encoded by SMOC1 has recently been shown to play a critical role in limb development; its expression in prostate tissue is dependent on sex hormones, and it has been implicated in the sexually dimorphic development of the gonads. We put forward the hypothesis that SMOC1 provides a link between prenatal hormone exposure and digit ratio.
    Human Genetics 12/2012; 132(4). DOI:10.1007/s00439-012-1259-y · 4.52 Impact Factor
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