Image Description: cast of the skeleton of Lucy, an Australopithecus afarensis fossil
Researchers have discovered a new species of ancient ape that provides hints as to how bipedal walking evolved in modern humans.
The species, given the scientific name Danuvius guggenmosi, was found in clay pits in south-eastern Germany, in the state of Bavaria.
Four individuals were discovered: one male, two females and a juvenile. They were uncovered between 2015 and 2018, and the findings were published in the journal Nature earlier this month.
Upon piecing together the fossilised skeletons, a number of features of the bone structure of this species strongly suggest that it walked on two legs. For example, the spine shows a high degree of flexibility in the lower back just like in modern humans. This would mean that the weight of the torso would have been distributed over the hips of the ape, allowing it to remain balanced whilst walking on two legs.
Furthermore, analysis of the leg structure provides even more evidence that this ape walked bipedally. In particular, the ankles and knees are specially adapted to be able to bear more load, an adaptation which suggests that the legs were especially important in carrying the weight of the animal.
Interestingly, although its legs and spine indicate that this new species was bipedal, its arms and hands still resemble those of tree-climbing species, suggesting that it had a unique way of moving that combined walking on two legs with swinging from branches. This new finding therefore provides an important “missing-link” between our tree-climbing ancestors and modern walking humans.
The finding is significant because it suggests that the evolution of bipedal walking occurred much earlier than previously thought. Bipedal walking had previously been thought to have originated six million years ago. This new fossil, however, has been dated as being 11.62 million years old, meaning that our ancestors had been able to walk on two legs for a lot longer than we had realised.
It was previously believed that modern humans had gained the ability to walk by first transitioning through a period of knuckle-walking, as observed in modern chimps and gorillas.
This new discovery turns the accepted sequence of events on its head; it now appears as though humans retained the ability to walk from ancient apes such as Danuvius guggenmosi whilst chimps and gorillas evolved their knuckle-walking from a bipedal ancestor.
Other researchers, however, have cast doubt over exactly how much can be learned from these new findings. In particular, the incomplete, distorted remains of the new ape species make it much more difficult to make precise predictions about how it moved.
Additionally, more sophisticated evolutionary analysis is required before a direct line of descent can be made from the newly discovered Danuvius guggenmosi and Homo sapiens. Even if it turns out that we are not its direct ancestors, it could still provide valuable information on the evolution of bipedalism as would indicate that bipedal walking evolved on more than one occasion.
The evolution of bipedal walking was a critical step in the rise of modern man, enabling our ancestors to touch and explore the world in a new way, opening up the possibility of using tools. The fact that modern humans walk on two legs is one that sets us apart from every other living ape and is something that evolutionary biologists have struggled to explain. It is hoped that this new discovery will bring new evidence that may help researchers answer this question.
Image Credit: Anonymous via Wikimedia