Sexual dimorphism in Australopithecus afarensis revisited: How strong is the case for a human-like pattern of dimorphism?

Plavcan, J. Michael; Lockwood, Charles A.; Kimbel, William H.; Lague, Michael R.; Harmon, Elizabeth H.

doi:10.1016/j.jhevol.2004.09.006

Cited by 90 publications

(56 citation statements)

References 22 publications

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“…Their approach has an advantage of pooling fragmentary fossil data and increasing sample size. However, in providing a solution to a problem, their approach may be more problematic in its methodology (Plavcan et al, 2005). Reno and colleagues assume that the relationship between a metric variable and femoral head is the same for all individuals of a given taxon, regardless of locomotor adaptation.…”

Section: Discussionmentioning

confidence: 99%

Patterns of size sexual dimorphism in Australopithecus afarensis: Another look

Lee

2005

HOMO

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Section: Discussionmentioning

confidence: 99%

Patterns of size sexual dimorphism in Australopithecus afarensis: Another look

Lee

2005

HOMO

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“…The debate has been reviewed in detail in a series of publications [4,6,[9][10][11] and hinges on a number of methodological issues that could significantly impact the estimated levels of dimorphism (reviewed in [6]). …”

Section: Introductionmentioning

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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“…Although a strong association between those characteristics and reduced dimorphism in body mass, canine size and skeletal dimensions has been shown for many primate taxa (Kay et al, 1988;Plavcan, 1993;Ford, 1994;Smith and Jungers, 1997), there are taxa in which the relationship is less clear (Milton, 1985;Kappeler, 1990;Lindenfors and Tullberg, 1998), has not been thoroughly examined (e.g., Pithecia), or has been evaluated relying on small collections of museum specimens or wild specimens of uncertain provenance and\or unknown sex and age (e.g., Aotus, Callicebus). Studies on larger sample sizes of sexually dimorphic free-ranging polygynous and polyandrous primates have illustrated some of the problems of assuming average population measurements from small samples of any particular location (Goldizen et al, 1988;Altmann et al, 1993;Jablonski and Ruliang, 1995;Turner et al, 1997;Schmid and Kappeler, 1998;Pochron and Wright, 2003;Johnson et al, 2005;Glander, 2006).Behavioral reconstructions of early hominins are regularly based on the observed behavior and morphology of extant primates (Plavcan and Van Schaik, 1997;Lovejoy, 2009;Takai et al, 2009;Gettler, 2010) and the taxonomic classification of fossils is influenced by our understanding of between and within population variation in the extent of sexual dimorphism, as well as possible changes in body size and dimorphism with latitude (Reno et al, 2003;Plavcan et al, 2005). In other words, our understanding of early hominin behavior and taxonomy will benefit from answering the following questions: What is the range of variation in sexually dimorphic physical traits of extant primates?…”

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confidence: 99%

Rensch's rule, Bergmann's effect and adult sexual dimorphism in wild monogamous owl monkeys (Aotus azarai) of Argentina

Fernández-Duque

2011

American J Phys Anthropol

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Some monogamous primates are characterized by biparental care, territoriality, and a reduced level of physical dimorphism. In others, the relationship between those behavioral patterns and dimorphism is less clear. I tested Bergmann's and Rensch's rules using Aotus spp. body mass data and I characterized the extent of sexual dimorphism in body mass, dental and physical measurements in a socially monogamous owl monkey population (n = 91 adults) from the Argentinean Gran Chaco. A. azarai azarai from the Argentinean Chaco is larger than the more tropical owl monkey species (r = 0.7, N = 6 species), but there is no apparent increase in sexual dimorphism with increased body mass. The body masses of adult male and female A. a. azarai were remarkably similar (Mean = 1.26 kg); there were no marked sex differences in most skeletal measurements, but males had higher and wider upper and lower canines than did females. Body mass and neck circumference were positively and strongly related (r = 0.533, n = 52), and the body mass of adults was not a reliable indicator of their age (r = 0.03, n = 10). The data illustrate the complexities inherent in examining and summarizing within population variation in skeletal and nonskeletal measurements and contribute to a better understanding of the relationships between monogamous behavioral patterns and sexual dimorphism.

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Sexual dimorphism in Australopithecus afarensis revisited: How strong is the case for a human-like pattern of dimorphism?

Cited by 90 publications

References 22 publications

Patterns of size sexual dimorphism in Australopithecus afarensis: Another look

Patterns of size sexual dimorphism in Australopithecus afarensis: Another look

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

Rensch's rule, Bergmann's effect and adult sexual dimorphism in wild monogamous owl monkeys (Aotus azarai) of Argentina

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