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The energetic cost of running is relatively high in man. In spite of this, humans are adept endurance runners, capable of running down, for example, zebra and kangaroo. Distance running is made possible for man in part by an exceptional ability to dissipate exercise heat loads. Most mammals lose heat by panting, which is coupled to breathing and locomotor cycles during running. This interdependence may limit the effectiveness of panting as a means of heat dissipation. Because sweating is not dependent on respiration, it may be more compatible with running as a thermoregulatory mechanism. Furthermore, man's lack of body hair improves thermal conductance while running, as it facilitates convection at the skin surface. While horses, for example, have been shown to possess energetically optimal speeds in each gait, the energetic cost for a man to run a given distance does not change with speed. It is hypothesized that this is because bipedality allows breathing frequency to vary relative to stride frequency. Man's constant cost of transport may enable human hunters to pursue the prey animal at speeds that force it to run inefficiently, thereby expediting its eventual fatigue. Given what is known of heat dissipation in Old World Anthropoidea, the bipedality of early hominids, and human exercise physiology, one factor important in the origin of the Hominidae may have been the occupation of a new niche as a diurnal endurance predator.
Man the Hunted argues that primates, including the earliest members of the human family, have evolved as the prey of any number of predators, including wild cats and dogs, hyenas, snakes, crocodiles, and even birds. The authors’ studies of predators on monkeys and apes are supplemented here with the observations of naturalists in the field and revealing interpretations of the fossil record. Eyewitness accounts of the ‘man the hunted’ drama being played out even now give vivid evidence of its prehistoric significance. This provocative view of human evolution suggests that countless adaptations that have allowed our species to survive (from larger brains to speech), stem from a considerably more vulnerable position on the food chain than we might like to imagine. The myth of early humans as fearless hunters dominating the earth obscures our origins as just one of many species that had to be cautious, depend on other group members, communicate danger, and come to terms with being merely one cog in the complex cycle of life.
A method, which was found to be accurate within 0.54 m/s(2), was developed to estimate the relative contributions of the net joint moments to forward progression and support in the gait of five normal subjects. Forward progression was produced primarily by the ankle plantar flexors with a significant assist from the knee extensors. Support was produced largely by the plantar flexors during single limb support and by a combination of ankle plantar flexors, knee extensors and hip extensors during double limb support. (C) 1997 Elsevier Science B.V.
Striding bipedalism is a key derived behaviour of hominids that possibly originated soon after the divergence of the chimpanzee and human lineages. Although bipedal gaits include walking and running, running is generally considered to have played no major role in human evolution because humans, like apes, are poor sprinters compared to most quadrupeds. Here we assess how well humans perform at sustained long-distance running, and review the physiological and anatomical bases of endurance running capabilities in humans and other mammals. Judged by several criteria, humans perform remarkably well at endurance running, thanks to a diverse array of features, many of which leave traces in the skeleton. The fossil evidence of these features suggests that endurance running is a derived capability of the genus Homo, originating about 2 million years ago, and may have been instrumental in the evolution of the human body form.