Stages of human evolution

The sign separating great apes from humans is considered to be brain mass, equal 750 g. It is with such a mass of the brain that a child masters speech. The speech of ancient people was very primitive, but it constitutes a qualitative difference between the higher nervous activity of man and the higher nervous activity of animals. At the beginning of our century, English geneticists discovered a gene whose action is directly related to articulate speech. Its mutation leads people to articulation disorders. Interestingly, this gene differs by only two single nucleotide substitutions from the same gene in chimpanzees. Thus, speech appeared, and the word denoting actions, labor operations, objects, and then generalized concepts, became the most important means of communication between people.

Speech contributed to more effective interaction between members of the primitive herd in labor processes, the transfer of accumulated experience from generation to generation, i.e. learning. In the struggle for existence, those primitive herds of ancient people gained an advantage, who began to take care of the elderly and support individuals who were physically weak, but had experience and stood out for their mental abilities. Previously useless old people, eaten by their fellow tribesmen when there was a shortage of food, became valuable members of society as carriers of knowledge. Speech contributed to the development of the thinking process, the improvement of labor processes, and the evolution of social relations.

In the process of becoming a person, there are three stages (Table 23.1):

• 1) ancient people
• 2) ancient people",
• 3) modern people.

Ancient people. It is believed that the most ancient people arose about 1 million years ago. Several forms of ancient people are known: Pithecanthropus, Sinanthropus, Heidelberg man and a number of others (Fig. 23.3). Outwardly, they already looked like a modern person, although they were distinguished by powerful supraorbital ridges, the absence of a chin protrusion, and a low and sloping forehead. The mass of the brain reached 800-1000 g. The brain had a more primitive structure than that of the later forms. The earliest people successfully hunted buffaloes, rhinos, deer, birds. With the help of hewn stones, they butchered the carcasses of dead animals. They lived mainly in caves and knew how to use fire. At the same time, there were quite a few forms of ancient people who stood at different stages of development and evolved in different directions (including gigantism).

The most promising direction of evolution was a further increase in the volume of the brain, the development of a social way of life, the improvement of tools, the wider use of fire (not only for heating and scaring away predators, but also for cooking). All other forms, including giants, quickly disappeared.

Ancient people (Neanderthals). To ancient people include a new group of people who appeared about 200 thousand years ago. They occupy an intermediate position between the most ancient people and the first modern people. Neanderthals were a very heterogeneous group. The study of numerous skeletons showed that in the evolution of Neanderthals, with all the diversity of the structure, two lines can be distinguished.

Rice. 23.3. One of the forms of the most ancient people is the Pithecanthropus, referred to the species Straight Man (Homo erectus)

One line went in the direction of powerful physical development. They were creatures with a low sloping forehead, a low occiput, a continuous supraorbital ridge, an underdeveloped chin protrusion, and large teeth. With a relatively small stature (155-165 cm), they had extremely powerfully developed muscles. The mass of the brain reached 1500. It is believed that Neanderthals used rudimentary articulate speech.

Another group of Neanderthals, apparently descended from the oldest forms independently of the first, was characterized by more subtle features - smaller brow ridges, a high forehead, thinner jaws and a more developed chin. In general physical development, they were noticeably inferior to the first group. But in return, they have significantly increased the volume of the frontal lobes of the brain. This group of Neanderthals fought for existence not by strengthening physical development, but through the development of intra-group ties during hunting, while protecting themselves from enemies, from adverse natural conditions, i.e. through the unification of the forces of individuals. This evolutionary path led to the appearance of Homo sapiens 40-50 thousand years ago - Homo sapiens.

For some time, Neanderthals and the first modern humans coexisted, and then, about 28 thousand years ago, the Neanderthals were finally supplanted by the first modern humans - Cro-Magnons.

The first modern people. The Cro-Magnons were tall - up to 180 cm, with a high forehead, the volume of the cranium reached 1600 cm 3. A continuous supraorbital ridge was absent (Fig. 23.4).

Rice. 23.4. Cro-Magnon - a representative of the species Homo sapiens (Homo sapiens)

To date, at least four genes associated with brain size in humans and other primates have been well studied. Mutations in these genes in humans lead to the development of a serious disease - microcephaly (from lat. micro- small and Greek. ancephalon- brain), accompanied by a decrease in brain volume by more than 70%. Comparative genetic analysis of the genomes of humans and great apes showed significant changes in the group of these genes during evolution, they were especially stormy during the divergence of humans and monkeys.

Computational comparison of genomes made it possible to identify more than two hundred more regulatory genes that cause the inclusion and deactivation of the above-described genes located next to them.

Thus, although the number of genes that determine brain development is small, changes in them can significantly change the human brain by affecting the activity of many interacting genes.

Cro-Magnons were articulate, as evidenced by a well-developed chin protrusion. A well-developed brain, the social nature of labor led to a sharp decrease in a person’s dependence on the external environment, to the establishment of control over certain aspects of the habitat, to the emergence of abstract thinking and attempts to reflect the reality around them in artistic images - rock paintings, bone figures, etc. .

Human evolution got out of the leading control of biological factors and acquired a social character. The main stages of the formation of a person are shown in the diagram (Fig. 23.5).

Rice. 23.5. The main stages of human development

The role of labor in the origin of man. Such features of a person as a highly developed central nervous system and speech as a means of communication between people, the separation of functions of the upper and lower limbs, an unspecialized hand capable of producing hundreds of various and subtle movements, the creation of a society instead of a herd, were the result of human labor activity. This qualitative peculiarity of human evolution was pointed out by F. Engels in his work “The Role of Labor in the Process of the Transformation of Apes into Humans”. Such traditional ideas have been confirmed in molecular genetic studies of the human genome. One of the regulatory regions of the human genetic material has undergone the greatest changes in comparison with great apes. It turned out that the human version of the genes allows you to control the activity of genes in the wrist and thumb, but the ancestral form of regulatory genes cannot do this. This fact indicates the morphological changes in the human hand, which allowed people to maintain the accuracy and dexterity necessary for the production and use of thin and complex tools.

Table 23.1

The main stages of human evolution

The ending