A new study by Jeremy DeSilva, anthropologist at Worcester State College in Massachusetts suggests that human ancestors may not have been good tree climbers. He suggests that our ancestors traded in arboreal adaptations to evolve bipedality.
By recording how wild chimpanzees climb tree in Uganda's Kibale National Park, DeSilva found that chimpanzees flex their ankles 45 degrees from normal resting position while modern humans flex their ankles a maximum of 20 degrees while walking. Flexing any more than that and a modern human's ankle will suffer serious injuries.
DeSilva then compared the ankle joint, the tibia and the talus, in great apes and fossil hominins between 4.12 million to 1.53 million years old. He found that all of the hominin ankle joints resembled those of modern humans rather than those of apes, suggesting that this joint "form" took on its current configuration early in human evolution.
Read the full ScienceNOW article.