2010 Vol 101.pdf (1.63mb) - Primate Society of Great Britain

Application of the comparative method in reconstructing extinct
primate social behaviour
K. Balolia
Department of Anthropology, University College London
The comparative method has had some application to date in reconstructing
the social behaviour of extinct primates, in that many researchers have used
observed level of skeletal dimorphism in extant primates to make inferences
about mating systems of extinct taxa. However, in this context, the
comparative method is limited in its application to the reconstruction of
primate social behaviour in that dimorphism alone is not able to distinguish
between specific types of mating behaviour (Plavcan, 2000; J Hum Evol 39,
327-344).
A new approach to the study of extinct hominin social behaviour by
Lockwood et al. (2007; Science 318, 1443-1446) showed that Paranthropus
robustus males underwent extended development into adulthood and
matured later than females to attain a high level of cranial dimorphism. In
taking this approach, they provided new scope for considering the
relationship between social behaviour and morphology using a comparative
framework. Through measuring overall levels of sexual dimorphism
combined with size and shape changes in the adult skull of Pan, Gorilla,
Pongo, Hylobates and Papio, I show how this approach, in conjunction with
methodological advances in quantifying cranial morphology, can be used to
investigate the relationship between morphology and intrasexual
relationships in primates. In addition to males showing prolonged growth to
attain full adult size, I consider the suggestion that cranial size and shape
changes occur, which relate to social dominance, both in males and in
females. Associated implications for future attempts to reconstruct extinct
primate social organisation using a comparative framework are discussed.
Digit ratios and social systems in fossil hominids
E. Nelson
School of Archaeology, Classics and Egyptology, University of Liverpool
Social systems underpin many aspects of primate behaviour and predicting
the social systems of extinct hominids (great apes) is critical for
understanding human palaeobiology, as well as social and cognitive
evolution. However, predicting social systems from fossils is problematic
due 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 length ratio (2D:4D), a putative
biomarker for prenatal androgen effects, co-varies with social systems
across haplorrhines; polygynous species have significantly lower 2D:4D
ratios (high prenatal androgen effects) than pair-bonded species. This study
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