According to the results, two main factors determine the energy consumption: the stride length and the active muscle mass. The shorter the steps and the more muscle mass needed for walking, the more energy-consuming it was. In particular, he benefits from his long legs and his favorable center of gravity: he lies just above the hips and knees, so that the short muscles at the ankles are mainly needed for walking. In contrast, the chimpanzee with its center of gravity in front of the hip must activate the large thigh muscles and consume more energy.
Regarding the evolution of the upright aisle, the individual differences between the chimpanzees are particularly interesting, the researchers said: They showed that even small changes can have a big effect, because the chimpanzee with the favorable energy consumption on two legs only took longer steps than his conspecifics. Perhaps there were such deviations even in the last common ancestor of humans and apes, speculate the researchers. Those who consumed less energy when searching for food, for example, had advantages over the others, so that this peculiarity could have prevailed over time. They now want to use fossils of early humans to check whether their physique already had corresponding changes.Michael Sockol (University of California, Davis) et al .: PNAS, DOI: 10.1073 / pnas.0703267104 ddp / science.de? Ilka Lehnen-Beyel advertisement