Alexander Markov, a doctor of biology and head of the biological evolution sub-department at Moscow State University’s biology department and the evolutionary theory specialist spoke to Sputnik about the reasons behind the deterioration of the human gene pool.
On the freezing of the gene pool:
“There’re two reasons, two important fundamental mechanisms which are evolving now, that work against us, that is, towards the erosion of the human population’s gene pool, at least in developed countries where there’s more or less a decent standard of living, or indeed in the vast majority of countries.”
“The first one is the relaxation of selection against deleterious mutations: those that have always historically been harmful. For example, those that ruin our health, and degrade the performance of our immune systems, brain and other organs. Previously most of the people with diseases [and those] with very weak health died, even in their childhood and in infancy (until recently infant mortality rate had been huge), and there was a kind of “sorting out” of harmful mutations. However, at the end of the 19th and in the first half of the 20th century, there was a revolution in the field of social welfare, medicine evolved, the problem of hunger was solved; [society introduced] disability pensions, rehabilitation programmes, antibiotics etc. As a result, infant mortality in developed countries has declined to pretty close to zero. So almost everybody survives and, consequently, the selection process almost doesn’t work. Of course, it works at the embryonic stage but it’s most likely not sufficient to be enough, as many of the harmful effects of deleterious mutations reveal themselves later.”
“In recent years, the speed of human mutagenesis has been identified with very high precision. It’s now done by comparing the entire genomes of parents and their children. This is a way to count the number of new mutations a child has that the parents didn’t seem to have. We know that now an average newborn has about 70 new mutations that their parents didn’t have. That’s insane. We don’t know how many of them are harmful, but, roughly speaking, taking into account that 9/10 of our genome isn’t vital for survival (so-called ‘junk DNA’), 9/10 of our genome goes there. But, nevertheless, there’s 1/10 left and that is, let’s say, 7 mutations that go to significant parts of the genome. Some of these mutations will be neutral (even if they come to any significant parts they won’t spoil anything) but there will also be some deleterious mutations. These are harmful because they ruin certain subsystems of our body. For example, muscle performance worsens, or the skeleton grows more slowly, renal system performance worsens; the brain is more likely to perform worse. You can estimate genome performance by the performance of the brain, as a lot of genes that our body has, are involved in the neurodevelopment and the work of the brain.
“Hundreds or thousands of genes should function smoothly and properly for us to have a brain that functions properly. So that will much likely affect cognitive abilities. There’s a huge amount of mutagenesis which is not offset by corresponding selection. That means an inevitable accumulation of harmful mutations for generations. Our genetic pool will degrade very fast, apparently because of the relaxation of selection.”
“The relaxation of selection is only one issue. It’s a debatable how much harm this problem is doing to us. Perhaps, while the population is growing rapidly, it’s not that harmful as there’s almost no selection. Everybody survives including good genotypes. Ill genotypes also survive but the population is growing. We seem not to be losing anything. But when, at some point, the population evens out, if there are those genotypes that survive accidentally, regardless of their quality, then the degeneration will become faster than during the ultra-fast population growth.”
“The second issue isn’t theoretic but proved by geneticists. Quite recently, in 2016-2017, the results of a large study conducted in the USA and in Iceland were published. The research was conducted on a sample of about 20,000 people, in other words, full human genomes, in the US and on a sample of more than 100 thousand people in Iceland. This very competent and very extensive study shows that everything is much worse: harmful genetic variants are not just accumulating, they’re supported by the selection and allow people to better reproduce in the current context. What we consider bad genes, that, for example, degrade our intelligence, are spreading. They’re spreading because it turns out that in our modern age (apparently, for 100 or even 150 years) there has been a tendency that stupid people, uneducated people, reproduce better.
“It’s believed that intelligence and education aren’t inherited characters and instead depend on the environment, upbringing, culture or social stratum. However, geneticists have proven that such characteristics as level of education and cognition, that is — any measure of intelligence, according to any related test [reveals that] genes have a great impact on any of these characteristics, there’s high heritability. A person’s level of education is about 40-50% dependent on their genes, it also 50-60% dependent on the environment and chance. Perhaps, the more just the society is, and the less wealth and social inequalities prevail, the more genes contribute to such things. Then, education and intelligence have a high level of heritability and the adverse selection applies to them. It’s all proven; there are numbers and diagrams. People genetically predisposed to grow up intelligent and educated not only have fewer children, they have babies a year or two later. But that’s enough to create a huge selection pressure against genes [that can be positively correlated with] intelligence and education.”
“So, from the point of view of genetics, humanity isn’t doing well at the moment.”
On the differences between Russian and French people.
“Russians are a huge patchwork. That is, genetically, the Chukchi and, for example, the Karelians are at opposite poles among non-African people. The Russian population of central Russia and the French population don’t differ much. There are some differences in the frequency of occurrence of some neutral polymorphisms. If we take the entire genomes of 100 Russians and 100 French and process them via certain programs, and count all the polymorphisms, they should at least divide into two clusters. So we’ll be able to say that one part is one thing and the other part – another. Although the majority of these differences are neutral and don’t have any impact on any characteristics that are important, they still can be used to identify relationships. But generally it’s a European population. So the differences between Russian and French people are much weaker than, let’s say, the differences between the Russians and the Afro-Americans or the Russians and the Yakuts. But no program can distinguish Russians from Ukrainians or Belarusians.”
Sourse: sputniknews.com
