Differences in the 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line

Kratochvíl, Lukáš; Flegr, Jaroslav

doi:10.1098/rsbl.2009.0346

Cited by 57 publications

(89 citation statements)

References 19 publications

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“…However, the pattern in Lissotriton, Mesostriton, and Triturus is not clear because as the presence of sex differences in 2D:4D were not confirmed in all limbs. This unclear pattern may be caused by allometry (Kratochvıl and Flegr, 2009;Kolarov, 2013). However, according to latest studies, digit ratio is independent of body size in humans and non-human animals (Burley and Foster, 2003;Rahman et al, 2005;McIntyre et al, 2006;Chang, 2006;Manning, 2010;Almasry et al, 2011;Gomes and Kohlsdorf, 2011).…”

Section: Discussionmentioning

confidence: 99%

Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

Kaczmarski

Kubicka

Tryjanowski

et al. 2015

The Anatomical Record

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Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. It is considered to be a suitable biomarker of the in utero balance of fetal sex hormones, which affect early development of individua ls behavioral and morphological characteristics. In recent decades, digit ratio attracted a great attention in biology and psychology. However, for unmasking the biological basis of the phenomenon, extensive studies on nonhuman animals are necessary. Despite it was hypothesized that digit ratio is well conserved in all Tetrapoda, and there exist studies on mammals, birds, and reptiles, there are only two such study on anuran amphibians. Therefore, the aim of this study is to investigate the 2D:4D in the most basal salamanders, Caudata. We have studied digit ratio in four species of newts: Triturus cristatus, Mesotriton alpestris, Lissotriton montandoni, and Lissotriton vulgaris, using museum collection. We used computerized measuring of each limbs photos. We have found out that, in M. alpestris, females 2D:4D of all four limbs were significantly larger than in males. In L. montandoni and L. vulgaris, only 2D:4D of rear limbs significantly differed, in females being larger. In T. cristatus, digit ratios of males and females did not statistically differ. Thus, the results confirmed our hypothesis that at least in M. alpestris, L. montandoni, and L. vulgaris, females seem to have larger 2D:4D comparing to males, the pattern known from most mammals and opposite to birds, reptiles and anuran amphibians.

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Section: Discussionmentioning

confidence: 99%

Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

Kaczmarski

Kubicka

Tryjanowski

et al. 2015

The Anatomical Record

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“…In fact, the similarity of intercepts suggests that human digits are probably very close to being isometric. Hence, contrary to Kratochvíl and Flegr (2009), human digit ratio appears to be fairly independent of absolute size and therefore no allometric adjustments are required. In Fig.…”

Section: Example 2: Making Negative Size Dimorphism Disappearmentioning

confidence: 99%

“…It is easy to imagine that most researchers would agree with their conclusion. Moreover, three follow-up studies have discussed and examined the propositions of the Kratochvíl and Flegr (2009) study in great detail (Höne-kopp and Watson, 2010;Manning, 2010;Tobler et al, 2011). Although all of them, by various means, reach the conclusion that digit ratio remains sexually dimorphic even when accounting for allometry, none of the studies questions the validity of using OLS regression.…”

Section: Example 2: Making Negative Size Dimorphism Disappearmentioning

confidence: 99%

“…Recently, Kratochvíl and Flegr (2009) claimed that all or most of this might be caused by a statistical artifact of using a ratio that is not sizeindependent. Using an OLS regression of the length of the second over the length of the fourth finger, they find that this regression line does not pass through the origin, but instead has a positive intercept (a AE SE ¼ 11.2 AE 1.7 mm, P < 0.00001).…”

Section: Example 2: Making Negative Size Dimorphism Disappearmentioning

confidence: 99%

“…Hence, I generated a data set more or less closely following the parameters from the original Kratochvíl and Flegr (2009) …”

Section: Example 2: Making Negative Size Dimorphism Disappearmentioning

confidence: 99%

See 2 more Smart Citations

Women have Relatively Larger Brains than Men: A Comment on the Misuse of General Linear Models in the Study of Sexual Dimorphism

Forstmeier

2011

The Anatomical Record

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General linear models (GLM) have become such universal tools of statistical inference, that their applicability to a particular data set is rarely questioned. These models are designed to minimize residuals along the yaxis, while assuming that the predictor (x-axis) is free of statistical noise (ordinary least square regression, OLS). However, in practice, this assumption is often violated, which can lead to erroneous conclusions, particularly when two predictors are correlated with each other. This is best illustrated by two examples from the study of allometry, which have received great interest: (1) the question of whether men or women have relatively larger brains after accounting for body size differences, and (2) whether men indeed have shorter index fingers relative to ring fingers (digit ratio) than women. In depth analysis of these examples clearly shows that GLMs produce spurious sexual dimorphism in body shape where there is none (e.g. relative brain size). Likewise, they may fail to detect existing sexual dimorphisms in which the larger sex has the lower trait values (e.g. digit ratio) and, conversely, tend to exaggerate sexual dimorphism in which the larger sex has the relatively larger trait value (e.g. most sexually selected traits). These artifacts can be avoided with reduced major axis regression (RMA), which simultaneously minimizes residuals along both the x and the y-axis. Alternatively, in cases where isometry can be established there are no objections against and good reasons for the continued use of ratios as a simple means of correcting for size differences.

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2012

A Handbook for the Assessment of Children's Behaviours

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Differences in the 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line

Cited by 57 publications

References 19 publications

Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

Women have Relatively Larger Brains than Men: A Comment on the Misuse of General Linear Models in the Study of Sexual Dimorphism

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