Susana Carvalho from the University of Cambridge (UK), Tetsuro Matsuzawa from the University of Kyoto (Japan) and their colleagues tried to establish the origin of bipedalism (walking on two legs) by observing how chimpanzees compete for food resources.
It turned out that monkeys stand on their hind limbs when they need to grab as much food as possible - it is much more convenient to do it with your hands. Hence the conclusion: our ancestors may have lived in difficult conditions, when certain resources were not easy to find. This situation persisted for a long enough time for this adaptation to pass through natural selection and was fixed in the form of anatomical features of subsequent hominids.
This is just one of a number of hypotheses. The fossil record does not allow us to conclude about when our ancestors became bipedal, so speculation continues to multiply. Perhaps the most generally accepted assumption is that the climate played a key role: forests were replaced by savannahs, and human ancestors had to move long distances on the ground, rather than jumping from tree to tree.
The new study is digging deeper in search of specific circumstances that, in a given context, have exerted corresponding evolutionary pressures. Don't just run - transfer resources!
Experts conducted two experiments. Both passed in the Bossu forest (Guinea). In the first, chimpanzees were given access to the nuts of the oil palm and the kula tree of the olax family. The former are widespread, while the latter are an “unpredictable resource” that is, it is not.
Chimpanzees found themselves in three situations: when only oil palm nuts were available, when there were few kula nuts available, and when kula nuts were the main resource. In the second case, the monkeys tried to carry the largest number of nuts at one time. In the third experiment, the chimpanzees were calmer, but ignored the oil palm nuts as less valuable.
It is easy to see that in the second case, the competition for resources was especially fierce, and chimpanzees climbed on their hind limbs four times more often.
Promotional video:
The second experiment was conducted as part of a 14-year observation of chimpanzees in the same forest plundering crops. In 35% of cases, monkeys got up to carry more at a time. And here again the factor of “unpredictable resource” played - chimpanzees could not know in advance what the farmers “prepared” for them.
Probably, our ancestors behaved in the same way: in a situation where it was not known whether there would be a valuable resource in this place next time, they stood on their hind limbs and grabbed as much as possible.