The cost of bipedalism

Locomotion represents a significant energy cost for most vertebrates. Within the hominoid primates, hominins have adapted to a very particular type of locomotion that is considered one of their most important characteristics. Whereas non-human primates are arboreal creatures or terrestrial quadrupeds, hominins have adopted not only posture but also bipedal locomotion on a permanent basis. It should be pointed out, however, that occasional bipedal locomotion can be commonly observed in other primates. Habitual bipedal locomotion has completely freed the hand from the functions of suspension in trees or body support during quadrupedal walking, and its anatomy has been profoundly modified as a result, making various forms of precision grasping or forceful grasping possible. The human pelvis, which supports the viscera, and the spinal column have also been strongly affected by this evolution. But it is undoubtedly in the lower limb that the most spectacular skeletal and muscular changes have been observed. Humans arenot only adapted to bipedal walking, but also to endurance running at a relatively modest energy cost, given the long distances that can be covered. This adaptation has enabled the Homogenus to develop a very specific type of predation. In the fossil record, traces of bipedal posture have been recognized in the earliest forms of hominins, which nevertheless retained significant arboreal movement capabilities. With the Australopithecus genus , the adaptation to walking became more pronounced, but it was only in the Homo genus that this emancipation from arboreal environments came to an end, and the adaptation to endurance running appeared.