Extended Male Growth in a Fossil Hominin Species

Department of Anthropology, University College London, Gower Street, London WC1E 6BT, UK.
Science (Impact Factor: 33.61). 12/2007; 318(5855):1443-6. DOI: 10.1126/science.1149211
Source: PubMed

ABSTRACT In primates that are highly sexually dimorphic, males often reach maturity later than females, and young adult males do not show the size, morphology, and coloration of mature males. Here we describe extended male development in a hominin species, Paranthropus robustus. Ranking a large sample of facial remains on the basis of dental wear stages reveals a difference in size and robusticity between young adult and old adult males. Combined with estimates of sexual dimorphism, this pattern suggests that male reproductive strategy focused on monopolizing groups of females, in a manner similar to that of silverback gorillas. However, males appear to have borne a substantial cost in the form of high rates of predation.

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Available from: Jacopo Moggi-Cecchi, Aug 05, 2014
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    • "This scenario highlights the importance of male contest competition during human evolution, which is arguably more likely than other mechanisms of sexual selection to have shaped modern human behavior (Puts 2010). Interestingly, recent evidence from specimens of Paranthropous robustus from the same general time period as Homo erectus suggests that males had an extended period of growth, suggestive of intense male competition after attainment of reproductive maturity (Lockwood et al. 2007). Male competition is often thought to have been less important for Homo erectus owing to the decreased sexual dimorphism in this taxon compared to earlier hominins (though this notion has recently been questioned; see Antón 2003), and this has further been interpreted as suggestive of a transition from polygamy to monogamy (Plummer 2004) owing to the general association between monogamy and monomorphism in nonhuman primates (cf. "
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    ABSTRACT: Multi-level societies are unique in their ability to facilitate the maintenance of strong and consistent social bonds among some individuals while allowing separation among others, which may be especially important when social and sexual bonds carry significant and reliable benefits to individuals within social groups. Here we examine the importance of social and sexual bonds in the multilevel society of hamadryas baboons, Papio hamadryas, and apply these principles to social evolution in Plio-Pleistocene hominins. The behavior, adaptations and socioecology of baboons (Papio spp.) have long been recognized as providing an important comparative sample to elucidate the processes of human evolution, and the multi-level society of hamadryas baboons in particular shares even more similarities with humans than other baboons. Here we draw parallels between processes during the evolution of hamadryas social organization and those characterizing late Pliocene or early Pleistocene hominins, most likely Homo erectus. The higher costs of reproduction faced by Homo erectus females, exacerbated by an increased reliance on difficult to acquire, nutrient-dense foods, are commonly thought to have been alleviated by a strengthening of male-female bonds (via male provisioning and the evolution of monogamy) or by the assistance of older, post-reproductive females (via grandmothering). We suggest that both of these social arrangements could have been present in Plio-Pleistocene hominins if we assume the development of a multi-level society such as that in hamadryas baboons. The evolution of a multi-level society thus underlies the adaptive potential for the complexity that we see in modern human social organization.
    International Journal of Primatology 05/2012; 33(5):1165-1193. DOI:10.1007/s10764-012-9600-9 · 1.99 Impact Factor
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    • "For the Swartkrans hominid femur sample, measurable diaphyseal sections are only preserved on SK 82 (AP diameter ¼ 24.8 mm; transverse diameter ¼ 30.4 mm; playtmeric index ¼ 81.6) and SK 97 (AP diameter ¼ 23.3 mm; transverse diameter ¼ 35.3 mm; playtmeric index ¼ 66.0) (Robinson, 1972). size also seems to support the hypothesis of a high level of BSSD in the species (Lockwood et al., 2007). "
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    ABSTRACT: Member 1 of the Swartkrans Formation is comprised of two sedimentary infills, the Lower Bank (LB) and the Hanging Remnant (HR). Together, the LB and HR preserve fossils of early Homo and Paranthropus robustus, Earlier Stone Age lithic artifacts, purported bone digging tools and butchered animal bones. Collectively, this evidence was the first to establish the co-existence of two early Pleistocene hominid species and also led to inferences of plant root harvesting and meat-eating by one or both of those species. P. robustus is the more abundant of the two hominids at Swartrkrans, represented in Member 1 by hundreds of fossils that derive from at least 99 individuals. Thus, Swartkrans Member 1 stands as the world's single largest repository of that extinct species. Here we add to the Member 1 sample of hominid fossils with descriptions of 14 newly discovered specimens.
    Journal of Human Evolution 03/2012; 62(5):618-28. DOI:10.1016/j.jhevol.2012.02.003 · 3.73 Impact Factor
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    • " skeletal ruggedness of the sample , so it is inferred for good reason they are all male . This leaves small , young crania without the delicate features of females ; these are inferred to be males , who , although adult with erupted M 3 s , did not survive long enough to grow to complete maturity and the full physical bulk achieved by old males . Lockwood et al . ( 2007 ) used these observations to reconstruct social organization in A . robustus : " Extended male growth occurs in primates when male reproductive success is concentrated in a period of dominance resulting from intense male - male competition … Climbing the dominance hierarchy typically involves not only an increase in size but also change"
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