Are there genetic differences between races and peoples? Yes, and this is a fact long established by science. Thanks to genetic mutations in some parts of the world, they are poisoned with milk and do not tolerate alcohol at all, while in others, beans threaten people with sudden death. But the same genetic diversity allows science to look into the distant past of mankind and provides important clues to medicine.
In the 80s of the last century, the world was swept by a panic wave associated with the detection of the AIDS virus. Humanity has felt completely unprotected in the face of a deadly disease that can occur as a result of infection with the immunodeficiency virus. The slogans of "free love" of the previous era were forgotten: now they talked more and more about "safe sex", dangerous razors disappeared from hairdressing salons, and in medicine, a bet was made on everything disposable.
Later it turned out, however, an interesting thing: there are people who are resistant to HIV infection. In these people, the mutation has disabled the gene for the chemokine receptor, which encodes a protein that acts as a landing site for the virus. No site - no infection. Most of these people are in Northern Europe, but even there they are no more than 2-4%. And the "landing site" for the virus discovered by scientists has become the target of developing therapeutic drugs and vaccines against HIV.
Anti-AIDS - no AIDS
The most striking thing in this story is not even that, for some reason, it was in Northern Europe that a certain number of people were found who were not afraid of the "plague of the 20th century." Another thing is more interesting: the mutation, and with practically the modern frequency, was present in the genome of the Northern Europeans as far back as … 3000 years ago. How could this happen? Indeed, according to the data of modern science, the AIDS virus mutated and “migrated” from African monkeys to humans no earlier than the 20s of the last century. He has not been in the form of HIV for hundreds of years!
Peoples and genes
Population is a biological concept, and it can be studied using biological methods. The people are not necessarily a genetic unity, but a cultural and linguistic community.
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Nevertheless, it is possible to distinguish populations comparable to individual ethnic groups and to identify genetic differences between them. It is only necessary to understand that the differences between people within one ethnic group will always be greater than the differences between the groups themselves: the interpopulation differences will account for only 15 percent of the total number of differences. Moreover, these differences can be harmful, neutral and only in a certain case useful, adaptive.
If we take genetic differences over large areas, then they will line up in some geographic patterns associated, for example, with climate or the intensity of UV radiation. An interesting question is the change in skin color. In the conditions of the African ancestral home of humanity with its scorching rays of the sun, all mutations that create light skin invariably were culled by selection. When people left Africa, and ended up in geographic areas with a large number of cloudy days and low intensity of UV radiation (for example, in northern Europe), selection, on the contrary, supported such mutations, since dark skin in such conditions prevents the production of vitamin D, which is necessary for calcium metabolism. Some peoples of the Far North, however, retained a relatively dark skin, since they replenish the lack of vitamin D from venison and liver of marine animals. In areas with variable intensity of UV radiation, due to another genetic mutation, the skin was able to form a temporary tan.
Africa is the cradle of humankind, and the genetic differences between Africans are much greater than between Europeans and Asians. If we take the genetic diversity of Africa for 1000, then the rest of the world from this thousand accounts for 50.
Obviously, the once arisen mutation of the chemokine receptor gene was fixed by selection in the northern European region, since it gave the advantage of survival against the background of the spread of some other viral infection. Its penetration into the human body took place using a molecular mechanism similar to AIDS. What kind of infection it was is now not known exactly, but it is more or less obvious that the selection, which gave an advantage to the owners of the mutation, went on for millennia and was already recorded in the historical era. How was this established?
As already mentioned, 3000 years ago, among the inhabitants of the region, the "anti-AIDS" mutation already had an almost modern frequency. But the exact same frequency is found among Ashkenazi Jews, who originally settled in Germany, and then migrated to neighboring areas of Central and Eastern Europe. Jews began to settle en masse in Europe 2,000 years ago after the defeat of the anti-Roman uprising in the 1st century AD. and the fall of Jerusalem. In addition to the Ashkenazi (Germanic) branch, there was also a southern, "Sephardic" branch, with a localization mainly in Spain.
In the homeland of Jews, in Western Asia, a mutation of the chemokine receptor gene was also encountered, but with a frequency of no more than 1–2%. This is how it remained among the Jews who have lived for generations in Asia (Palestine, Iran, Iraq, Yemen), in North Africa, as well as among the Sephardim. And only Jews living in the region close to Northern Europe have acquired a local high mutation rate. Another example is the gypsies who came from India to Europe about 1000 years ago. In their homeland, the mutation rate was no more than 1%, but now it is 15% among European Roma.
Of course, both in the case of the Jews and the case of the Roma, there was an influx of genes from the outside due to mixed marriages. But the existing estimates in science do not allow attributing such an increase in frequency to this factor alone. Natural selection was clearly at work here.
Humanity clock
It is known that mutations in the human genome occur constantly, they work as a kind of biological clock by which it is possible to establish how the distant ancestors of mankind migrated: first they settled in Africa, and then, leaving their native continent, and throughout the rest of the world, except Antarctica. In these studies, mitochondrial DNA, transmitted through the female line, and male Y chromosomes, transmitted through the male line, provide the greatest assistance. Neither the genetic information of mitochondria, nor a part of the genome stored in the Y-chromosome, practically does not participate in the recombination of genes that occurs in the sexual process, and therefore go back to the genetic texts of the foremother of mankind - "mitochondrial Eve" - or some African "Adam", Y- which chromosomes are inherited by all men on Earth. Although mtDNA and Y chromosomes did not recombine, this does not meanthat they came from the ancestors unchanged. It is precisely the accumulation of mutations in these two repositories of genetic information that most reliably demonstrates the genealogy of humanity with its endless branching and dispersal.
Congenital vulnerability
Obviously, there are regional populations on earth, or even whole ethnic groups, in the genome of whose representatives mutations have developed that make these people more vulnerable.
And not only when drinking alcohol, but also in the face of certain diseases. Hence, the idea may arise of the possibility of creating a genetic weapon that would strike people of one race or one ethnic group, and would leave representatives of others unharmed. When asked whether this can be done in practice, modern science answers "no." True, one can jokingly speak of milk as an ethnic weapon.
Considering that about 70% of the Chinese population suffers from genetically predetermined lactase deficiency, and digestion is impaired by the consumption of milk in most Chinese adults, it is possible to disable the PRC army by sending it to latrines, if, of course, you find a way to give it milk - More serious an example is the intolerance of legumes among residents of a number of Mediterranean countries, which is described in the article. However, even the pollen of leguminous plants will not allow to disable, say, only all Italians in a multinational crowd, and in fact it is this kind of selection that is meant when they talk about fantastic projects of ethnic weapons.
However, mutations occurring in the part of the genome to be recombined, that is, in the X chromosomes, are much more significant for humans and humanity. In the study of adaptation, more attention is paid to mutations that have arisen in the part of the genome to be recombined - that is, all chromosomes except the Y chromosome. Moreover, the age of these mutations can also be tracked. The fact is that next to the part of DNA that has undergone a mutation there are other completely recognizable regions of the chromosome (possibly carrying traces of other, older mutations).
During recombinations, fragments of parental chromosomes are intermixed, but at the first stages, the environment of the mutation of interest to us will be preserved. Then new recombinations will gradually fragment it and bring new "neighbors". This process can be estimated in time and an approximate time of occurrence of the mutation of interest to us can be obtained.
Ethnogenomics data allow, based on the history of the accumulation of mutations, to trace the history of the exodus of mankind from the African ancestral home and spread across all inhabited continents. These data at certain time intervals can be supplemented with data from linguistics and archeology.
From the point of view of an individual organism or community in which one or another mutation frequency is observed, mutations can be neutral or negative, or they can carry an adaptive potential. It can manifest itself not at the place of origin of the mutation, but where its effect is most in demand and will be supported by selection. And this is one of the important reasons for the genetic diversity of peoples on the ethnological map of the world.
And this applies not only to alcohol consumption, but also to certain diseases. Hence, the idea may arise of the possibility of creating a genetic weapon that would strike people of one race or one ethnic group, and would leave representatives of others unharmed. When asked whether this can be done in practice, modern science answers "no." True, one can jokingly speak of milk as an ethnic weapon.
Sobriety mutation
In the example already cited, a mutation that gives resistance to AIDS is present with low frequencies in India, the Middle East, and southern Europe. But only in the north of Europe its frequency jumped up sharply. There is another similar example - a mutation leading to alcohol intolerance. In the 1970s, during studies of liver biopsy preparations in the Chinese and Japanese, it was found that representatives of these Far Eastern peoples have a very active liver enzyme, alcohol dehydrogenase, which converts alcohol into acetaldehyde - a toxic substance that does not give intoxication, but poisons the body.
In principle, the processing of ethanol into acetaldehyde is a normal stage in the body's struggle with ethanol, but this stage should be followed by the second - the oxidation of acetaldehyde by the enzyme aldehyde dehydrogenase and the production of harmless, easily removed components. But this second enzyme was not produced in the examined Japanese and Chinese at all. The liver quickly turned alcohol into poison, which was then not excreted from the body for a long time.
Hence, instead of "high" after the first glass, a person received tremors in his hands, redness of the facial skin, nausea and dizziness. It is highly unlikely that such a person could become an alcoholic.
As it turned out, the mutation that gives rise to aversion to alcohol arose around the beginning of agriculture somewhere in the Middle East (there is still a frequency of about 30% among Arabs and Asian Jews). Then, bypassing India (through the steppes of the Black Sea region and southern Siberia), it ended up in the Far East, where it was supported by selection, covering 70% of the population. Moreover, in Southeast China, its own version of the "anti-alcohol" mutation appeared, and it also spread over a large territory up to the steppes of Kazakhstan.
All this means that in the Far East there was a high demand for such a mutation among local populations, just … we must remember that this happened several thousand years ago, and alcohol was practically not present in human culture. Where did anti-alcohol genes come from?
Obviously, at one time they also came to the court as a means of fighting some kind of infection, and then - lo and behold! - it so happened that in both the Far and the Middle East there are now many people who genetically do not accept drunkenness. This whole story, like the story of the AIDS resistance gene, perfectly shows that this or that mutation in the past could have been supported by selection not at all on the basis of which it was discovered in our time.
And what about Russia? In Russia, the mutation responsible for aversion to drinking has a frequency of 4%, that is, no more than 10% of the population are carriers. Moreover, we are talking about both mutations - both in the Middle East and in the Chinese variants. But even with the combined forces they did not take root in us, so in the fight against drunkenness, genes are of no help to us.
A cure or an Achilles heel?
During the Korean War, US Army soldiers suffering from malaria were given a drug called primaquine. The pharmacological action of this drug was to destabilize the erythrocyte membrane. The fact is that the malarial plasmodium, penetrating into the blood, "captures" the erythrocyte and develops inside it. To make it more convenient to develop, plasmodium destabilizes the erythrocyte membrane.
It was then that primaquine appeared, which literally knocked out a wedge with a wedge. He additionally "softened" the membrane weakened by the plasmodium, and it burst. The malaria causative agent could not develop further, the disease receded. And what happened to the rest of the erythrocytes that were not captured by the plasmodia? But nothing. The action of the drug passed, the membrane stabilized again. But this was not the case for everyone.
A number of soldiers who took primaquine died from hemolysis - the complete destruction of red blood cells. When they began to investigate the issue, the following became clear. First, all the deceased had a deficiency in the enzyme glucose-6-phosphate dehydrogenase, which was responsible for stabilizing erythrocyte membranes, and this deficiency stemmed from a genetic mutation. And secondly, the deceased soldiers were of either African American or Mediterranean ancestry. The mutation, as it turned out, was found only in some peoples.
Today it is known that approximately 16-20% of Italian men (this effect is not manifested in women) are at risk of death from hemolysis, and not only after taking primaquine (which weakens the already weak erythrocyte membranes and leads to their mass death).
These people are also contraindicated in beans and some other foods and medicines that contain strong oxidants. Even the smell of bean pollen can cause a fatal reaction. The strange nature of this mutation ceases to be strange if we consider that it was supported by selection precisely in the places where malaria was spread and was a kind of “natural” primaquine.
In addition to Italy, a relatively large number of carriers of the mutation is noted in Spain, and its frequency is about 2% in North Africa and Azerbaijan. In Soviet times, it was even decided to ban the cultivation of legumes in the Azerbaijan USSR, so frequent were cases of favism, that is, the occurrence of hemolysis from contact with beans.
Winners are all
The science of ethnogenomics, which has been actively developing in recent years, which studies the genetic characteristics of races and ethnic groups, as can be seen at least in the examples given, is a completely applied discipline. It is closely related to pharmacogenomics, which studies the effect of drugs on people with different genetic characteristics, including those characteristic of certain ethnic and racial groups.
Indeed, for some of them, some drugs can be harmful (for example, primaquine), and some, on the contrary, are much more effective. In addition, ethnogenomics has become a great help in compiling a picture of the preliterate history of mankind and its languages, based on scientific data, and not on myths.
And one of the main conclusions that we can draw today from research on ethnogenomics is that with all the diversity of mankind, there is no reason to talk about genetically more or less developed peoples. All living generations are champions of life, for their ancestors managed to survive the harsh vagaries of nature, epidemics, long migrations and give a future to their offspring. And genetic diversity is just a memory of what biological mechanisms helped different parts of humanity to adapt, survive and win.
Svetlana Borinskaya