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In the absence of a fossil record, hypotheses about how bipedalism started Until now they focused on a plantigrade quadruped ancestor, which stepped with all its feet like modern monkeys, or on another suspended four-legged animal, similar to modern chimpanzees. But nevertheless, the discovery of the remains of an extinct 11.6 million-year-old ape contradicts previous theories.
Danuvius guggenmosi, as they have called the new species, it was the first bipedal ape according to the team of scientists, led by the Eberhard-Karls-Universität Tübingen in Germany, which has discovered his remains in the Allgäu region of Bavaria.
The fossils found correspond to at least four individuals (one male, two females, and one juvenile) and include fully preserved limbs, vertebrae and fingers and toes. Thanks to these bones, researchers have been able to reconstruct the way Danuvius moved in his environment. The image of its locomotion shows that it was unlike that of any known living creature.
"For the first time, we have been able to study several functionally important joints, including the elbow, wrist, hip, knee and ankle, in a single fossil skeleton of that age," Madelaine Böhme, from the department of German university geosciences and first author of the study published this week in the journal Nature.
The analysis reveals a hitherto unknown movement: that this ape was climbing with outstretched limbs. The results thus indicate that the origin of bipedalism occurred in trees, or in an arboreal context, before reaching the ground. In addition, these first apes did not go through a stage in which they walked hunched over, the authors note.
“We deduced that bipedalism was perfectly adapted to the trees because of its opposable big toe, which was not only very long and strong, but also rotated laterally (to provide better opposition to the other toes) and could be hyperflexed to grip with small diameter brackets. He could walk upright because he could balance his body and chest on his hips ”, Böhme details.
How did D. guggenmosi walk?
Due to the morphology of the bones, this ape could have hung from the branches with its arms. But unlike other ‘relatives’, such as gibbons or orangutans, who do not use their legs as much as their arms for locomotion, this species had hind limbs that were held straight and could have been used for walking.
“Danuvius was like an ape and a hominin at the same time. Regarding the former, because of the slightly elongated arms (like those of bonobos, but not as long as those of gorillas, orangutans or gibbons) and because of the opposable big toe ”, underlines the researcher, for whom this animal shows the conditions in which both great apes and humans diverged.
Thus, one of the aspects that most astonished the research team was the similarity of certain Danuvius bones to humans, compared to the great apes. “Personally, I was very surprised by the great similarity of the morphology of the vertebrae and tibiae with those of humans (hominins), in contrast to apes. It was totally unexpected for all of us ”, commented the expert.
In that sense, the group highlights how even the elbow of the new species of ape discovered is not like that of the great apes, it looks more like humans or small primates.
Actually D. guggenmosi, which was similar in appearance to a bonobo just over a meter in height, combined characteristics of bipedal (wide thorax, elongated lumbar spine, and extended hips and knees) and dangling ape (elongated and fully extended forelimbs).
Although important fossils of its anatomy are still missing to confirm these results, the team suggests that Danuvius bipedalism was common almost 12 million years ago in a European ecosystem. "If Danuvius is really a great ape (and not a hominin or human), what defines the latter if not the usual bipedalism?" Asks Böhme.
According to the authors, this article not only revolutionizes our view on the evolution of bipedal locomotion, but also may create a dilemma for paleoanthropology in the anatomical definition of hominins.
Madelaine Böhme et al. "A new Miocene ape and locomotion in the ancestor of great apes and humans"Nature 6th November 2019.