![]() ![]() ![]() for Denmark, must be considered as exceptionally high. ![]() A typical male 2D : 4D level of 1.02, as reported by Bang et al. As for evidence from countries in proximity to Denmark, male mean 2D : 4D levels are 0.93 in Finland ( Manning et al., 2000), 0.95 in Sweden ( Sanders et al., 2005), 0.95 in Lithuania ( Manning, 2002), 0.955 in Belgium ( Millet and Dewitte, in press), 0.96 in Germany ( Manning et al., 2000 Kempel et al., 2005) and 0.99 in Poland ( Manning et al., 2000).įrom the existing data, it appears that Northern European males of Scandinavian descent have comparatively low 2D : 4D. that the observed average 2D : 4D value of 1.02 in Danish men was only ‘slightly higher’ than averages found for men in the UK (0.99, according to Bang et al., but most UK studies yielded 0.97 or 0.98), this constitutes a very large group difference of about one and a half standard deviation units. Hence, contrary to the assertion of Bang et al. Sample standard deviations for 2D : 4D generally are about 0.03. Not even female samples with a mean 2D : 4D as high as 1.02 are known. Importantly, the entire 2D : 4D literature (more than 80 reports, with samples from more than 25 different countries or ethnic groups from five continents) does not contain a single male sample with a mean 2D : 4D larger than unity. Geographical (population or ethnic) variation in typical 2D : 4D levels is marked ( Manning et al., 2000, 2003, 2004a Peters et al., 2002) and currently poorly understood. Presently, there are no other 2D : 4D data from Danish men that could serve as a reference point. is unlikely to be responsible for this finding (iii) single measurements of sex hormones might be too unreliable to capture presumably subtle associations with 2D : 4D. Here, we present arguments and evidence on the following: (i) observing mean 2D : 4D levels beyond unity in males, particularly from Northern European descent, is an unexpected and interesting finding (ii) the 2D : 4D measurement method of Bang et al. First, average 2D : 4D was 1.02 in the total sample and second, finger lengths were measured from hand outline drawings (an unvalidated 2D : 4D measurement method). Hence, assuming that these were spurious (type I errors) rather than real effects, the authors concluded that ‘measurements of finger lengths do not have the power to predict the testicular function of adult men’ (Abstract). Out of 14 correlations, they found only two to be statistically significant, but mutually contradictory. investigated associations between right 2D : 4D, various testicular, semen and sex-hormone parameters in a sample of 360 young men from the Danish general population. 2D : 4D has been shown to be a correlate of a suite of sex-dependent, hormonally influenced variables, including behavioural, cognitive, personality and somatic traits, adult-onset diseases and measures related to fertility and sexuality ( Manning, 2002 Putz et al., 2004 Cohen-Bendahan et al., 2005).īang et al. This hypothesis has generated much interest since then and, as is now discernible, has started off an expanding research program. In late 1998, it was suggested in an article published in Human Reproduction ( Manning et al., 1998) that 2D : 4D may be a useful biomarker for prenatal androgen action. The second-to-fourth digit ratio (2D : 4D) is a sexually dimorphic trait in humans: men tend to have lower 2D : 4D values than women. After review of the article, we have the following comments. We read with interest the advance-access publication of Bang et al.
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