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The energetic costs of load-carrying and the evolution of bipedalism

Watson, JC, Payne, RC, Chamberlain, AT, Jones, RK and Sellers, WI 2008, 'The energetic costs of load-carrying and the evolution of bipedalism' , Journal of Human Evolution, 54 (5) , pp. 675-683.

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    Abstract

    The evolution of habitual bipedalism is still a fundamental yet unsolved question for paleoanthropologists, and carrying is popular as an explanation for both the early adoption of upright walking and as a positive selection pressure once a terrestrial lifestyle had been adopted. However, to support or reject any hypothesis that suggests carrying efficiency was an important selective pressure, we need quantitative data on the costs of different forms of carrying behavior, especially infant-carrying since reduction in the grasping capabilities of the foot would have prevented infants from clinging on for long durations. In this study, we tested the hypothesis that the mode of load carriage influences the energeticcost of locomotion. Oxygen consumption was measured in seven female participants walking at a constant speed while carrying four different 10-kg loads (a weighted vest, 5-kg dumbbells carried in each hand, a mannequin infant carried on one hip, and a 10-kg dumbbell carried in a single hand). Oxygen consumption was also measured during unloaded standing and unloaded walking. The results show that the weighted vest requires the least amount of energy of the four types of carrying and that, for this condition, humans are as efficient as mammals in general. The balanced load was carried with approximately the predicted energy cost. However, the asymmetrical conditions were considerably less efficient, indicating that, unless infant-carrying was the adaptive response to a strong environmental selection pressure, this behavior is unlikely to have been the precursor to the evolution of bipedalism.

    Item Type: Article
    Themes: Health and Wellbeing
    Schools: Colleges and Schools > College of Health & Social Care
    Colleges and Schools > College of Health & Social Care > School of Health Sciences > Centre for Health Sciences Research
    Colleges and Schools > College of Health & Social Care > School of Health Sciences
    Journal or Publication Title: Journal of Human Evolution
    Publisher: Elsevier
    Refereed: Yes
    ISSN: 00472484
    Depositing User: RH Shuttleworth
    Date Deposited: 23 May 2012 16:17
    Last Modified: 20 Aug 2013 18:28
    URI: http://usir.salford.ac.uk/id/eprint/22753

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