Extreme mobility in the Late Pleistocene? Comparing limb biomechanics among fossil Homo, varsity athletes and Holocene foragers Colin N. Shaw a, b, * , Jay T. Stock a a PAVE Research Group, Department of Archaeology and Anthropology, University of Cambridge, Downing Street, Cambridge, Cambridgeshire CB2 3ER, UK b McDonald Institute for Archaeological Research, Department of Archaeology and Anthropology, University of Cambridge, Cambridge, UK article info Article history: Received 31 July 2012 Accepted 9 January 2013 Available online xxx Keywords: Peripheral Quantitative Computed Tomography (pQCT) Fossil hominin Diaphyseal cross-section Humerus Tibia abstract Descriptions of Pleistocene activity patterns often derive from comparisons of long bone diaphyseal robusticity across contemporaneous fossilized hominins. The purpose of this study is to augment existing understanding of Pleistocene hominin mobility patterns by interpreting fossil variation through com- parisons with a) living human athletes with known activity patterns, and b) Holocene foragers where descriptions of group-level activity patterns are available. Relative tibial rigidity (midshaft tibial rigidity (J)/midshaft humeral rigidity (J)) was compared amongst Levantine and European Neandertals, Levantine and Upper Palaeolithic Homo sapiens, Holocene foragers and living human athletes and controls. Cross- country runners exhibit significantly (p < 0.05) greater relative tibial rigidity compared with swimmers, and higher values compared with controls. In contrast, swimmers displayed significantly (p < 0.05) lower relative tibial rigidity than both runners and controls. While variation exists among all Holocene H. sapiens, highly terrestrially mobile Later Stone Age (LSA) southern Africans and cross-country runners display the highest relative tibial rigidity, while maritime Andaman Islanders and swimmers display the lowest, with controls falling between. All fossil hominins displayed relative tibial rigidity that exceeded, or was similar to, the highly terrestrially mobile Later Stone Age southern Africans and modern human cross-country runners. The more extreme skeletal structure of most Neandertals and Levantine H. sapiens, as well as the odd Upper Palaeolithic individual, appears to reflect adaptation to intense and/ or highly repetitive lower limb (relative to upper limb) loading. This loading may have been associated with bipedal travel, and appears to have been more strenuous than that encountered by even university varsity runners, and Holocene foragers with hunting grounds 2000e3000 square miles in size. Skeletal variation among the athletes and foraging groups is consistent with known or inferred activity profiles, which support the position that the Pleistocene remains reflect adaptation to extremely active and mobile lives. Ó 2013 Elsevier Ltd. All rights reserved. Introduction The relationship between biomechanically imposed loads and skeletal adaptation is quite complex (Pearson and Lieberman, 2004). Nevertheless, experimental research supports the general concept of bone functional adaptation, and the use of diaphyseal cross-sectional properties to explore patterns of habitual behavior among groups (Currey, 1984; Lanyon and Rubin, 1984; Martin and Burr, 1989; Rubin et al., 1990; Lanyon, 1992; Ruff et al., 2006). An- alyses of the femoral and tibial diaphyseal structure of Pleistocene Homo have concluded that while morphological variation is appa- rent, there has been little shift in locomotor ranging levels amongst the foraging populations from this period (c.f. Trinkaus and Ruff, 2012). Interpretations of Pleistocene mobility patterns, however, might be augmented through direct comparisons with more recent foragers and living humans where activity patterns have been better documented. Early analyses concluded that the Neandertal lower limb was better adapted to extended bouts of heavy physical activity com- pared with those of early modern humans (Trinkaus, 1989). This finding led to the suggestion that Neandertals spent comparatively more time moving continuously and/or vigorously across the landscape. This interpretation was later reconsidered (c.f. Trinkaus, 1997) following the implementation of methodology that better controlled for the influence of body size on diaphyseal geometric properties (Ruff, 2000a). Later analyses of Neandertals and Levan- tine anatomically modern Homo sapiens lower limb diaphyseal strength concluded that, once properly standardised, differences * Corresponding author. E-mail addresses: cns30@cam.ac.uk, cshaw111@mac.com (C.N. Shaw). Contents lists available at SciVerse ScienceDirect Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol 0047-2484/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jhevol.2013.01.004 Journal of Human Evolution xxx (2013) 1e8 Please cite this article inpress as: Shaw, C.N., Stock, J.T., Extreme mobility in the Late Pleistocene? Comparing limb biomechanics among fossil Homo, varsity athletes and Holocene foragers, Journal of Human Evolution (2013), http://dx.doi.org/10.1016/j.jhevol.2013.01.004