A modern man in everyday life uses all the advantages of upright walking, without thinking about this feature inherent in representatives of his biological species. But it was thanks to the release of the front limbs and straightening of the body that people at one time were able to learn how to perform rather complex labor actions, without which it would be impossible to create all the riches of civilization.
There are several independent hypotheses as to when and how a person became erect. One of them is associated with the so-called Miocene cooling. It is assumed that during the late Miocene, a harsh climate with low temperatures was established on Earth. The areas of tropical forests, where the ancestors of modern humans, habitual to the arboreal lifestyle, lived, have sharply decreased.
The adherents of this hypothesis believe that primates actually have only one opportunity to survive - to descend from the trees and adapt to the difficult conditions of terrestrial existence. Such a change directly contributed to a change in the structure of the body of primates and the nature of their movement. Gradually, the ancestors of man learned to move on the surface of the earth on straight legs, without leaning on the front limbs when walking, as monkeys do.
Until now, the labor concept of the emergence of bipedal locomotion is widespread, the author of which was one of the founders of Marxism, Friedrich Engels. He considered labor to be the decisive factor in the transformation of the great ape into man. The straightening of the body and the appearance of a gait that was not characteristic of animals was explained by Engels by the need to free the hands for performing labor operations.
Indeed, at some point, human ancestors needed to perform very complex movements, for example, to carry various objects, get food or make primitive tools. Gradually, the hand acquired its own specialization, and the human body straightened. Simultaneously with the development of the hand, the brain of primitive people also improved, thinking developed, and speech was formed.
When moving, the ancient man began to rely only on his legs, while his hands were free. This "biological improvement" allowed ancient people to make a giant leap in development, forever separating from the animal world. Simplifying Engels's views, we can say that upright walking was required in order to free up hands for those affairs without which society could not exist.
However, this theory, logical at first glance, is refuted by its critics by the fact that upright posture, as established by modern scientists, arose long before the moment when a person learned to make the most primitive tools of labor. The point of view seems to be correct, according to which the transition of the ancient human ancestors to upright posture is due to many interrelated biological and social factors, each of which cannot be considered in isolation from the general course of evolution of the human race.
