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


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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    • "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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    • " 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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