A report in the journal Nature mentions fossils from a previously unknown species dating back 11.6 million years that suggests a new form of "positional behavior" they call "extended limb clambering". The discovered ape, Danuvius guggenmosi, had complete limb bones, which were unearthed in southern Germany by a team led by Madelaine Boehme, a professor at the University of Tubingen. The scientists deduced that it would have been able to hang from branches by its arms. The limbs would also have been able to hold its hind limbs straight, with a foot that could have been put on the ground, they observed.
In their conclusive statement, the scientists wrote that with a broad thorax, long lumbar spine and extended hips and knees, as in bipeds, and elongated and fully extended forelimbs, as in all apes, Danuvius combines the adaptations of bipeds with apes that hang from tree limbs. The species are a model for the common ancestor of great apes and humans.
Danuvius guggenmosi may have been able to walk on its hind legs in the trees before it reached the ground, not afterward. Responding to the discovery, Tracy L. Kivell at the University of Kent in England asked if they evolved from an ancestor that lived mainly in the trees, or were these ancestors already walking on all fours on the ground and subsequently evolved to stand up and walk on two feet. She noted that the earlier deemed ancestors - African apes, chimpanzees, bonobos, and gorillas spend most of their time on the ground walking on their knuckles, though they climb into trees for food, protection and to sleep. On the other hand, orangutans walk standing on their hind legs along branches, an echo, some argue, of the ancestors of modern humans. She agreed to the fact that the fossil is the best model yet of what a common ancestor of humans and African apes might have looked like. She concluded that the model is likely to answer how and why our human ancestors became less dependent on life in the trees and fully embraced two-footed terrestrial locomotion.