Even from school, every person knows that all biological species are constantly evolving and changing. But does a person develop? To answer this question, you first need to understand what evolution is. In biology, this concept means the process of development of living nature, which is accompanied by genetic adaptations and changes. Today, there are several evolutionary theories that explain the mechanism of development. The most common is the synthetic theory of evolution.
This theory is a synthesis of genetics and classical Darwinism. Among the main provisions it can be distinguished the following: the elementary unit of evolution is the local population. That is, it is impossible to consider the changes in individual individuals, because they are not self-sufficient without their population. This is most noticeable among insects. For example, ants have a caste of workers, warriors, a female. An individual does not mean anything, so changes in it cannot affect the species as a whole.
Evolution occurs through recombination or mutational variability. Simply put, genes either change or connect in a new way.
The main driving force behind evolution is natural selection. Habitat conditions are constantly changing, which makes the species either adapt to them, changing, or die.
Neutral genes can be formed due to the principle of the founder or gene drift, that is, the process of replacing or displacing one gene by another while decreasing vital resources within the population. As a result, the population can change dramatically. The founder principle is a special case of gene drift. It means a high likelihood of the appearance of new species in the case of a large area populating a small population. As a rule, the genetic set of individuals does not differ in diversity and has a random character, but the newly formed species can be radically different from its predecessors.
A species is understood as a system of populations that are reproductively isolated from other populations. Simply put, different species cannot have common offspring that would be capable of reproduction.
The formation of species occurs in most cases in geographically isolated areas.
According to biological or social evolution, since the man left the animal state, he began to change the world around him. Initially, these changes were minimal and even imperceptible at first glance. However, this gave rise to a real revolution in wildlife. And natural selection stopped working. So, for example, if any living species got into conditions unsuitable for life, it would certainly die, but not people. At the very beginning of history, huge deserts were formed on the planet, although before that there was fertile soil and forests. Human ancestors used it to grow food. But the approach to the ground was wrong, as a result of which the soil became barren. The person moved to another place in order to do the same there.
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It should be noted that at the initial stage of human development, the power of natural selection was very high. In particular, the Neanderthals entered icy Europe much earlier than the Cro-Magnons, which gave them the opportunity to better adapt to new conditions. Their nostrils were very wide, which made it possible to better warm the surrounding space.
Human populations were also influenced by other factors of natural selection, including disease. But in the end, the person acquired the immunity that he has today.
Nowadays, natural factors have ceased to work. Every person who lives in a more or less developed country, regardless of biological nature, feels comfortable in a warm house and receives qualified medical care. And some idealists even begin to think about the time to create conditions suitable for life on other planets. All of this can mean one thing: natural selection no longer exists. But the biological species Homo sapiens exists. Taking into account modern means of transportation, it would be more correct to speak of one human planetary population.
But what happens to the human species? If we analyze the provisions of the synthetic theory of evolution, it becomes obvious that they are all connected exclusively with biological processes. This means that these processes also affect a person. Genes remain genes wherever their carrier is. Biological changes in the human population are also taking place. A striking example of this is the increase in average growth over the past centuries. The reason for these changes is the artificial evolution of species. Man-made changes that occur in the environment lead to changes within the population. But at the same time, this evolution has absolutely nothing to do with natural evolution. We can also say that biological evolution was directly dependent on social changes. So, for example,the emergence of new methods and ways of storing food has provoked changes in nutrition, which, in turn, leads to changes within the population. True, it is impossible to compare these processes in terms of speed. Social evolution is fast enough, while biological evolution takes many times more time.
In order to maintain or even improve the standard of living that exists at the present time, humanity must continue to change the world around it and create artificial evolution. At the same time, artificial or man-made evolution does not mean that it is controllable. Social change occurs uncontrollably and spontaneously and is subject exclusively to the personal interests of a small group of the rich. This means that poor people, that is, most of the world's population, will be forced, for example, to eat harmful foods. There can be a lot of similar examples. Despite the fact that it is not difficult to arrange controlled biological evolution, however, in a market society that is torn apart by contradictions, it is impossible. To make the changes necessary for humanity, society must be rebuilt.
Meanwhile, American scientists have proved that human evolution continues to this day. Back in 1948, a large-scale medical study began in the American town of Framingham. 5 thousand people of different ages were invited to participate in the experiment. Every two years these people were examined, and in 1971 their children were also involved in the experiment. Currently, doctors are working with the third generation. Moreover, 100 volunteers served science after their death, bequeathed their brains to neurophysiologists.
The results of the research are placed in a database, with the help of which scientists try to establish the extent to which the propensity to various diseases is inherited.
Several years ago, these studies interested the biologist S. Stirns from Yale University, who decided to study the changes that have occurred in generations. And he was able to prove that the modern human population is still evolving.
It is generally accepted in the scientific world that a person has not changed for a long time. Allegedly, the successes of modern medicine put an end to human evolution, because the carriers of "defective" genes not only live to old age, but also leave offspring, so there is no need to talk about natural selection. But Stearns refuted this hypothesis.
After comparing the results of medical examinations of volunteers from Framingham, in particular women of different generations, he caught a certain pattern: daughters differed from mothers in a number of parameters. In particular, this is the difference in proportions: daughters turned out to be more overweight than mothers. At the same time, the daughters had lower blood cholesterol and blood pressure levels. But the difference between generations did not end there. In the younger generation, menopause came later.
The study participants included women with Italian, Irish, French and English roots, but they all fell under the pattern found by Stearns.
The scientist took into account social differences, but they had very little effect on medical indicators. In addition, he tried to explain the difference between generations by the intervention of medicine, but the results of the examinations were not influenced by the women taking medicines. Before the examination, the women reported on the use of hormonal drugs, but after studying the list of these drugs, Stearns came to the conclusion that they had no effect.
All this gave the scientist grounds to assert that all his observations reflect the course of evolution. During the period of research, natural selection has taken place in the modern human population. And the difference between generations is the result of changes in the genotype.
Stearns built a mathematical model that can predict human evolution for many years to come. If evolution continues at the same pace as now, then in three centuries the weight of a woman leading a healthy lifestyle will increase by about 2 percent, but at the same time menopause will come a year later.
Colleagues of the scientist vigorously condemn the results of Stearns' research. They note that no one before has been able to follow the changes in the human body in such a short time for evolution. At the same time, scientists argue that only a large-scale genetic analysis can conclusively prove the existence of evolution in modern human society.
It is possible that this will happen soon. At the moment, more and more scientists are engaged in such observations. And now it has been possible to prove that man has evolved quite recently. So, in 2007, a group of geneticists from Helsinki compared the genomes of people of different nationalities in search of special forms of genes that are responsible for the normal absorption of lactose. This carbohydrate, found in milk, can cause severe stomach upset. According to the results obtained, the least common lactose intolerance is found in Europeans, but the inhabitants of Asia, almost all suffer from this congenital deficiency.
Milk began to be consumed in Europe almost 10 thousand years ago. At that time, lactose resistance was not very common in the population. However, over time, under the influence of natural selection, the variants of genes that made it possible to drink milk without problems came to the fore. Geneticists have proven that the generally accepted conclusions are not so simple. Scientists managed to find in the genotype of the inhabitants of the Basque Country and southern Italy variants of genes that determine resistance to lactose, which have not been previously described. These genes were not similar to each other, but they were united by the fact that they arose about 1.5 thousand years ago.
Thus, according to scientists, man continues to develop, and the process of evolution has never stopped. I would like to believe that in the future the human population will only get better, adapting as much as possible to the conditions of the surrounding world.