Bonobos have a more human-like second-to-fourth finger length ratio (2D:4D) than chimpanzees: a hypothesized indication of lower prenatal androgens

McIntyre, Matthew H.; Herrmann, Eva; Wobber, Victoria; Halbwax, Michel; Mohamba, Crispin; Sousa, Nick de; Atencia, Rebeca; Cox, Debby; Hare, Brian

doi:10.1016/j.jhevol.2008.12.004

Cited by 52 publications

(42 citation statements)

References 40 publications

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“…The relationship between social system and digit ratio across extant haplorrhines suggests that 2D : 4D reflects links between prenatal androgen effects (PAEs) and sexually selected social behaviours [26,27]. We have used this hypothesis to predict social systems of extinct hominids from digit ratios calculated from fossil remains.…”

Section: Discussionmentioning

confidence: 99%

Digit ratios predict polygyny in early apes, Ardipithecus , Neanderthals and early modern humans but not in Australopithecus

et al. 2010

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Social behaviour of fossil hominoid species is notoriously difficult to predict owing to difficulties in estimating body size dimorphism from fragmentary remains and, in hominins, low canine size dimorphism. Recent studies have shown that the second-to-fourth digit ratio (2D : 4D), a putative biomarker for prenatal androgen effects (PAEs), covaries with intra-sexual competition and social systems across haplorrhines; non-pair-bonded polygynous taxa have significantly lower 2D : 4D ratios (high PAE) than pairbonded monogamous species. Here, we use proximal phalanx ratios of extant and fossil specimens to reconstruct the social systems of extinct hominoids. Pierolapithecus catalaunicus, Hispanopithecus laietanus and Ardipithecus ramidus have ratios consistent with polygynous extant species, whereas the ratio of Australopithecus afarensis is consistent with monogamous extant species. The early anatomically modern human Qafzeh 9 and Neanderthals have lower digit ratios than most contemporary human populations, indicating increased androgenization and possibly higher incidence of polygyny. Although speculative owing to small sample sizes, these results suggest that digit ratios represent a supplementary approach for elucidating the social systems of fossil hominins.

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Section: Discussionmentioning

confidence: 99%

Digit ratios predict polygyny in early apes, Ardipithecus , Neanderthals and early modern humans but not in Australopithecus

et al. 2010

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“…However, these differences appear to be attributable primarily to elevated T in male chimpanzees, rather than elevated T in female bonobos. A recent analysis of digit ratios (2D : 4D; a proxy for in utero exposure to androgens) in chimpanzees and bonobos failed to find evidence for elevated prenatal exposure to androgens in female bonobos [98], shedding doubt on an organizational effect on the propensity toward female dominance in this species.…”

Section: Summary Conclusion and Future Directionsmentioning

confidence: 99%

The influence of androgenic steroid hormones on female aggression in ‘atypical’ mammals

French

Mustoe

Cavanaugh

et al. 2013

Phil. Trans. R. Soc. B

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Dimorphism on dominance and agonistic behaviour in mammals tends to be strongly biased toward males. In this review, we focus on a select few species of mammals in which females are as or more aggressive than males, and/or are dominant to males, and explore the role of androgenic hormones in mediating this important difference. While the data are not as clear-cut as those published on traditional laboratory mammals, our review highlights important endocrine substrates for both organizational and activational influences of steroids on female aggressive behaviour. We highlight areas in which further observations and experiments are crucial, especially the potential facilitative effects of androgens on female aggression. Finally, new and innovative techniques, including molecular genetics and receptor pharmacology, portend important insights into the ways in which androgenic hormones regulate aggressive behaviour in 'atypical' female mammals.

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“…Since 1875 3 , it is known that the length of the index finger, compared to the length of the ring finger, the 2D:4D ratio, is a sexually dimorphic trait, not only in humans 4 but also in bonobos 5 . Lower ratios are more common in men and ratios closer to one are more characteristic of women 6,7 .…”

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High 3D:5D ratio: A possible correlate of externalizing and internalizing problems: An exploratory study

et al. 2011

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-Background and Objectives:The second to fourth (2D:4D) digit ratio is a sexually dimorphic trait which has been studied to examine the association between fetal hormones and a variety of behaviors. Lower 2D:4D ratios, suggestive of exposure to higher levels of prenatal testosterone, have been associated with male-linked disorders, while higher 2D:4D ratios, suggestive of exposure to weaker prenatal androgen action, have been associated with female-linked disorders. Past research has concentrated on the 2D:4D ratio, whereas the relationship between other ratios, such as the 3D:5D ratio, and psychopathology has not much been studied before. Therefore, the aim of this study was to assess the correlation between the 2D:4D and 3D:5D ratio, and internalizing as well as externalizing symptoms, in a large non-clinical sample (143 boys, 150 girls) of white Caucasian children aged 7 to 13 years.Methods: Externalizing and internalizing symptoms were assessed with the Child Behavior Checklist (CBCL).Results: The 3D:5D ratio in boys and in girls was positively associated with scores on Externalizing Problems. Further, in girls only, the 3D:5D ratio was positively correlated to scores on Internalizing Problems.Conclusions: The 3D:5D ratio can be considered a correlate of externalizing and internalizing problems in children from the general population. In humans, the critical period in prenatal life for sexual differentiation starts around the 7 th -8 th week after conception 1 . Until this moment the genitalia are undifferentiated and the level of testosterone determines whether the fetus then starts to develop into male or female. Prenatal hormones that influence the sexual differentiation also have an effect on sexual differences in behavior.Fetal hormones and its effects on behavior can be studied in a variety of ways. Direct measurements such as hormone levels being extracted from the umbilical cord at birth or assessing hormonal levels of the fetus or the mother during pregnancy suffer from disadvantages due to their invasive nature, selection biases, and ethical considerations. Researchers interested in the effect of prenatal hormones on the behavior of children or adults, therefore often rely on indirect measures. Cohen-Bendahan and colleagues 2 described three indirect methods of examining the behavioral effects of prenatal exposure to sex hormones: otoaucoustic emissions, finger length ratio, and dermatoglyphics. In this paper, we will focus on finger length ratios.Since 1875 3 , it is known that the length of the index finger, compared to the length of the ring finger, the 2D:4D ratio, is a sexually dimorphic trait, not only in humans 4 but also in bonobos 5 . Lower ratios are more common in men and ratios closer to one are more characteristic of women 6,7 . The relative length of fingers is fixed for life within the first three months of pregnancy 6,8 . Finger length ratio is considered as a marker of the amount of testosterone the fetus was exposed to in the womb. A higher level of prenatal testosterone ...

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Bonobos have a more human-like second-to-fourth finger length ratio (2D:4D) than chimpanzees: a hypothesized indication of lower prenatal androgens

Cited by 52 publications

References 40 publications

Digit ratios predict polygyny in early apes, Ardipithecus , Neanderthals and early modern humans but not in Australopithecus

Digit ratios predict polygyny in early apes, Ardipithecus , Neanderthals and early modern humans but not in Australopithecus

The influence of androgenic steroid hormones on female aggression in ‘atypical’ mammals

High 3D:5D ratio: A possible correlate of externalizing and internalizing problems: An exploratory study

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