The upright gait strains the skeleton in a very different way than the monkey ankle. Image: M. Garde, Wikipedia
Reading The upright walk in the ancestors of man has come about as they have changed from the trees to a life on the ground. This is what US anthropologists Tracy Kivell and Daniel Schmitt say after evaluating the anatomy of living apes today. The researchers thus contradict the common theory among scientists, according to which the upright gait has developed in ancestors of humans, who already lived on the ground. Scientists have been discussing the question of when and how human ancestors began to walk upright since the days of Charles Darwin. Two theories have become established: The human being descends from an ancestor who supported himself with his knuckles while moving on the ground, is the first theory. From this ancestor could also descend the modern apes, which also move on the ground in this so-called ankle. The second explanatory model, on the other hand, assumes that walking on two legs began with an ancestor who still lived predominantly on trees and only occasionally entered the ground. Hints for this theory Kivell and Schmitt now believe to have found with their data.

In their study, the two researchers analyzed the bone structure of 104 chimpanzees, 43 bonobos and 91 gorillas and focused on how much they adapted during the course of evolution to the ankle traction typical of these monkeys. The scientists came up with great differences between the different species of monkey: While the gorillas showed only a very slight adaptation to the movement on the ground, the researchers found in the anatomy in bonobos and chimpanzees many more such typical features. From this, the scientists conclude that the ankle gland in gorillas has developed at a different time than chimpanzees and bonobos.

Based on this observation, Kivell and Schmitt believe that there was no common ancestor of humans and all great apes that already moved in the ankle. Rather, this locomotion has developed in the gorillas independently of the other monkeys. After all, humans are descended from an ancestor who still predominantly lived on trees and whose lifestyle resembled that of today's chimpanzees, the researchers believe. During his excursions to the ground, this ancestor began to walk on two legs. The anatomical clues, which already indicated an ankle walk on the ground in these early human ancestors, have been misinterpreted, the scientists explain: In reality, these traits were created as an adaptation to life on trees.

Tracy Kivell and Daniel Schmitt (Duke University, Durham): PNAS, doi 10.1073 / pnas.0901280106 ddp / science.de? Ulrich Dewald ad

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