Андрей Тихомиров
When and why did man appear?
Over the past 20 years, members of the international consortium Zoonomia have deciphered the genomes of animals from various families and compared them with the human DNA sequence. Biologists report that the results of many years of research have allowed them to better understand at what stage of evolution the changes occurred that made humans out of great apes. Science has established that the fundamental difference between man and animals occurred about a million years ago in South Africa. It was based on mutational processes that led to the fact that in the areas associated with the development of the brain of the “zone of accelerated human development”, the protein packaging of DNA was rearranged. These areas of the brain of ancient human ancestors accidentally happened to be next to enhancers – amplifiers of gene activity, which became a turning point in the history of ancient people. But this accident was also a necessity that arose, in all likelihood, with the change of food used by ancient ancestors, it was the use of food cooked on fire that served as this impetus.
Africa is the place where the first hominids appeared – anthropoid creatures. Until now, science has proceeded from the fact that there were three waves of migration from Africa to the Eurasian space: 2 million years ago it was Homo erectus, half a million years ago – the ancestors of the Neanderthal, and 50 thousand years ago – our ancestors, Homo sapiens. It is now possible to add to them, at least after the analysis of hereditary material, a fourth wave. It was most likely the Denisov man (Homo altaensis). For a long time, there was no consensus among scientists about exactly where on the continent a person appeared, either in the Awash National Park in Ethiopia, or in the Olduvai Gorge in Tanzania, or in South Africa. Theories have been put forward that the ancient ancestors of people did not appear in one particular point in Africa, but arose in its different parts. Now scientists have identified the place of human formation – South Africa.
In the process of human development, an important role was played by the fact that human ancestors ate both plant and animal food, this is the period of the early Paleolithic. Such a variety of food had a huge impact on the development of the entire body of human ancestors and especially the brain. Fishing, which developed from the end of the Paleolithic, also brought new food to ancient man, containing substances important for his development. But the main thing was that the ancient man mastered the fire and began to cook on it: fry and bake meat, fish, plants. This was carried out on coals, in hot ashes, on hot stones, in pits lined with stones. These ancient forms of food preparation were preserved for a long time among some peoples of Australia and Oceania. Animals, even the higher ones, are afraid of fire and in every possible way avoid meeting with it. Therefore, fried and boiled food can be eaten only occasionally as a result of garbage or by stealing food from a person.
It is known that a long stay of a person or animal on any one diet changes the secretory reaction of the glands to food stimuli, which is due to a change in the functional state of the food center. The food center is the formation of the central nervous system of humans and higher animals that regulates the intake of nutrients into the body and their processing in the digestive tract. The concept of a food center was introduced by I.P. Pavlov on the basis of his theory of conditioned reflexes. The work of the food center, due to the degree of satiety of the body and food irritants, causes the body to move for food, eating and secreting digestive juices. Like the respiratory center, the activity of the food center is periodic and regulated by changes in the chemical composition of the blood, stimuli associated with food intake, and agents acting on the interoreceptors of the alimentary tract, which in turn affect the brain. The so-called "hungry blood", that is, the blood of a person or animal a few hours after eating, excites the activity of the food center, and "well-fed blood", on the contrary, delays this activity. The food center consists of separate groups of cells located in various parts of the central nervous system, including the cerebral cortex. The food center is represented mainly by perceiving nerve cells, it is under the influence of other nerve centers and itself influences their activity. The change in the food base of ancient ancestors gradually led to changes in the digestive, nervous, and immune systems and served as an impetus for the formation of the II signaling system.
Since ancient times, fire has played a huge role in people's lives. Its use by man has become the cornerstone of the formation of a civilization that has its roots in the deepest antiquity. A group of archaeologists led by Francesco Berna from Boston University in the USA concluded in 2012 that man first began to use fire about 1 million years ago. Scientists came to this conclusion after discovering traces of hearths in the Vonderwerk cave in South Africa. Raw food held back the growth of brain volume in the ancestors of protohumans. Nutrient deficiencies in raw plant foods were the main cause of small brains in early human ancestors, confirming the key role of fire and "culinary arts" in human evolution, anthropologists say in an article published in Proceedings of the National Academy of Sciences also in 2012
Scientists have discovered a fundamental difference between humans and animals, which happened about a million years ago. Over the past 20 years, members of the international consortium Zoonomia have deciphered the genomes of 241 animal species from various families and compared them with the human DNA sequence. Biologists report that the results of many years of research have allowed them to better understand at what stage of evolution the changes occurred that made protohumans human. The term "zoonomia" (Zoonomia), after which the project was named, was introduced into scientific use by Erasmus Darwin (grandfather of Charles Darwin, 1731-1802, English physician, naturalist, inventor and poet): he expressed a bold idea for his time that that all warm-blooded animals are related to each other and had a common ancestor in the distant past. It took scientists more than two centuries to confirm this theory. In his chapter on biogenesis, Erasmus Darwin anticipated many of the ideas of Jean-Baptiste Lamarck, who was the first to develop a holistic theory of evolution.
In the early 2000s, the complete genomes of mice, humans, rats, and chimpanzees were published, which turned out to be very close, but there was not enough data for the study. This is how the Zoonomia project was born. More than 50 scientific organizations from different countries provided DNA samples to its participants. The results of the study were published in the form of 11 articles in the thematic issue of the journal Science. The task of the Zoonomia project participants was to identify the DNA features that determine species differences, and to find out at what stage in evolutionary history they were fixed at the genetic level. The studies concerned only representatives of the placental group, which appeared on the planet over the past 100 million years, and did not affect the more ancient marsupials and oviparous. Comparative genetics has allowed researchers to identify more than three million elements in human DNA, about half of which were previously unknown. It turned out that they play a crucial role in controlling all physiological processes in the body, and influence where, when and how much to produce proteins. It also turned out that approximately 11% of the genome (the so-called conserved DNA fragments) – about 4,500 regions in total – are identical in all mammals, including humans. They are necessary for the normal functioning of the body, and genetic changes in them can cause not only hereditary diseases, but also cancer.
Geneticists studying areas associated with brain development (“zones of accelerated human development” or HAR – Human Accelerated Regions) found that both humans and primates have them. But about a million years ago, differences began to appear – the protein packaging of DNA was rearranged. The "zones of accelerated human development" of the ancient human ancestors accidentally appeared next to enhancers – amplifiers of gene activity, which became a turning point in the history of the Homo sapiens species. An enhancer is a small section of DNA that, after binding transcription factors to it, stimulates transcription from the main promoters of a gene or group of genes. Enhancers are not necessarily located in close proximity to the genes whose activity they regulate, and are not even necessarily located on the same chromosome with them.
Each phenomenon in the world is formed under the influence of not only essential, necessary, but also random causes. Through the category of dialectics – necessity and chance, these phenomena can be explained. Necessity and chance do not exist without each other, they are an inseparable dialectical unity. The same connection, accidental in one respect, appears as necessary in another respect. Necessity does not exist in a "pure form", it manifests itself through chance. In turn, chance acts as a form of manifestation of necessity and its complement; it gives the phenomenon a certain originality, specificity, unique features. Ancient man, other living organisms belonging to a certain species, have common (specific) features that have arisen in the process of long-term development and are inherited. But these necessary signs always exist in an individual form, since a person and other living organisms differ from each other in size, shape, volume, etc. Some of these initially random traits for a species of a given species are fixed in the course of development, inherited and become necessary, and those of the necessary traits that turn out to be inappropriate in a different situation disappear, appearing in subsequent generations only in the form of a rudiment, that is, an accidental trait. . Thus chance turns into necessity, and vice versa, necessity turns into chance.
