Genes and environment

Steve Jones, Emeritus Professor of Human Genetics, Chief Researcher at University College London, Fellow of the Royal Society
Post -science

When it comes to genes and the environment, I often think of William Shakespeare. He wrote the play "The Tempest", and according to the plot, a shipwreck occurs on one island. A devil named Caliban lives on this island, and the people from the wrecked ship tried to treat him kindly, but he turned out to be absolutely terrible: he did not help them, but only hindered them. And in despair, one of them says: "On thy foul nature nurture will never stick" – this means that "you were born so terrible that no our actions, no upbringing will make you better."

In conversations about genetics, this idea often arises – the opposition of nature and nurture (nature vs. nurture). Few people know that this phrase itself goes back to Shakespeare. Francis Galton, who in a sense was the founder of human genetics, was fully convinced (as almost everyone was then) that everything depends on nature, that is, on how you were born. He was an outstanding scientist. Of course, he made mistakes, but all scientists make mistakes. Galton wrote a book called "The Heredity of Talent" (Hereditary Genius), in which he pointed out that if your father was a judge, and his father was a judge, and his father was a judge, then with a high probability you will also become a judge. But he went even further: he went to Newcastle upon Tyne (the Tyne is a river where rowing competitions are often held) and discovered that the rowing champions had fathers who were also champions, as well as their grandfathers and great-grandfathers. He tested his theory on various signs, and everything was repeated everywhere. For him, it proved that everything depends on your nature and no amount of education will change anything.

Of course, he was wrong. Among other things, money is also passed down through generations – and often through many generations: many modern millionaires became them because their parents were millionaires. Now, in our technological era, this is not true in all cases, but for a long time it was so. However, money genes do not exist. The very existence of repetitions is very weak evidence in favor of the influence of genes, but many still do not understand this. If you type the phrase "scientists have found a gene" into Google, the last time I did it, I got 63 thousand links. Considering that we have only 23 thousand genes, this is impressive. But all this is stupid: "scientists have found the gene for language", "scientists have found the gene for unhappiness", "scientists have found the gene for musicality", "scientists have found the gene for growth". The most dangerous thing in genetics is the phrase "the gene that is responsible for ...", because genes are just dull sections of DNA, they work only in the environment. Without the environment, they wouldn't work, and it's amazing when you study genetics. But the environment seems less important to society, whereas geneticists know that it is more important.

I often give a classic example from the genetics of cats. I have many examples from this field, and one of them is related to black and white cats. We all know that there are black and white cats. Charles Darwin, by the way, discovered a very interesting thing about white cats: all white cats with blue eyes are deaf. Darwin discovered this. It turned out that white cats do not produce the pigment melanin. We all have it: if you have dark hair, there is melanin in it; if you have dark skin, there is melanin in it, and it is also present in our brain, inner ear and other organs. A black cat can create melanin during the biochemical production chain: it starts with simple substances that combine to form this complex pigment. If one of the mechanisms in this chain is broken and the chain reaches this place and stops, you get a white cat. Everything is simple.

But sometimes the mechanism does not break completely, it is only slightly damaged and does not work quite correctly. Then cats have rather strange colors. I will tell you about Siamese cats – I don't know what they are called in Russian, but they are cats with a black nose, ears and tail, and if it is a cat, then he also has black testicles. The color of Siamese cats is a genetic mutation, their DNA is changed. We know what went wrong and where, we know the basis of this DNA chain well, what broke down there, we conducted breeding experiments with other cats, and everything repeats there according to the laws discovered by Mendel on peas. So these are genes. I'm happy to admit it, it's definitely the work of genes.

But what is important, it all depends on the environment. Cats acquire this strange color due to the fact that the enzyme responsible for the creation of melanin works well only in colder parts of the cat's body, where less excess energy affects the biochemical process, and works much worse in warm areas, that is, in the main part of the body, which is 2-3 degrees warmer. The nose, ears, tail and testicles, which are the coldest part of any man's body, turn black. If you want to get a dark Siamese cat, you can breed dark Siamese cats for many generations, or just take a Siamese kitten and keep it in a cold room, and it will become much darker. If you want to get a light Siamese cat, you can take a Siamese kitten and keep it in a warm room, and it will be much lighter. And if you want a very expensive black cat, you can take a Siamese kitten and keep it in the refrigerator, and you will get a black cat. So the color of the Siamese cat depends on the genes, but also depends on the environment. They work together, and we see it all the time.

We see how it works in our lives as well. When I was born, that is, 75 years ago – it's sad, but a fact: I was born at the end of World War II – after the war there was no serious famine, but there was some shortage of food, and there was a normalized distribution. In Russia and Germany it was even worse than in Western Europe, but people here were forced to stick to a simple diet. If you look back, you can understand that it was a very healthy diet: little sugar, little cakes and the like, almost no butter. And in general, people were quite thin. Since that time, everything has changed. And then, and in the XIX century, and in Russia of the XIX century, if you read Tolstoy, one of the key characteristics of the ruling class, that is, the rich, was that they were fat. The peasants were starving and were thin. The same thing happened here in Britain: if you read Charles Dickens, you will see that many rich characters-Londoners of the XIX century, in top hats and with cigars, were obese, and the poor were thin. Now we see the opposite situation. When I give a lecture about this to my students at University College London, I look at them – and they are very smart and all from the middle class – and I'm not sure I can find someone fat among them. But if I go to those parts of London where the working class lives, obesity is a big problem there. In America, this is a huge problem, life expectancy in the United States is falling rapidly, and this is due to obesity. Where did it come from? And food was freely available: in the 1930s, the average working-class person had to work more than half a week to provide food for himself, his wife and two children. Now it takes him on average less than a day to do this if he buys disgusting cheap, greasy, sweet food. Food is now publicly available, and people are eating it and gaining weight.

We know a lot about the genetics of this process. There is strong evidence that if individuals with specific genes eat a lot of food, they will become fat. But the effect of these genes is manifested only where there is cheap food. It's like the phenomenon of Siamese cats. If there is no food, it doesn't matter if you have the genes that will make you fat: you just don't have enough food to get fat. The effect of them is huge, but, very unexpectedly, they do not work in the intestines or liver, they do not change your metabolism – at least, most of them. They work in your brain, and almost all of them are related to appetite. There are various hormones that change the feeling of hunger, including insulin. But the first hormone discovered – and I will have to advertise University College London, because the discovery took place here, about 200 yards from here – is a hormone called ghrelin, the appetite hormone, discovered in 1903. We all know the feeling of hunger. We want to eat and go to McDonald's – whether in Paris, London, or Moscow – we buy some junk food there and eat it - well, I personally don't, and you probably don't either, but many people eat it and say, "Oh, it was delicious, wasn't it Lee?" And I think: "God, that's disgusting." But you don't go and buy a second or third cheeseburger or milkshake afterwards because you have other hormones that say: "You've had enough." These are satiety hormones. You have hunger hormones and "stop eating" hormones.

From time to time, people are born who do not produce these hormones, and they are always hungry. One of these hormones is called "leptin", and one person in 50 or 100 thousand is born without it. As a child, such people want to eat all the time, and they don't pretend: they are really insanely hungry. Of course, they scream, yell and make noise, their parents in frustration give them too much food, and they develop morbid obesity. Fortunately, we can now treat this with leptin injections. But this is again an example of the interaction of nature and the environment: these obesity or hunger genes have been present since the appearance of humans as a species, but they have become a problem only in the last 20-30 years, when food became available. This is a joint work of nature and the environment.

There is a second subtlety that people don't really like to think about: these genes affect your consciousness. They work in your head, and people are very worried that DNA can change your appetite. But I'll say, "It's a hormone." There is another hormone that also shows the interaction of nature and the environment and affects our consciousness – this is testosterone, the hormone that makes us men, beautiful creatures. Women also have it, but in smaller quantities, so some older women grow mustaches with age. Women have a little testosterone, but men have a lot more. Testosterone is a nasty thing: because of it, men live less, are more susceptible to infectious diseases, because it suppresses the immune system, and because of it, men are more likely to be killed.

Testosterone changes your behavior, and we know well how it happens, we know a lot about the biochemistry of this process. For example, bodybuilders who use testosterone to increase muscle mass often die for "male" reasons: they are killed, they die in car accidents, they commit suicide, and so on. So testosterone affects your mind. But in addition, it definitely changes your predisposition to violent behavior.

All over the world, men are killed ten times more often than women. The murder rate in Britain is quite low, although not the same as in Singapore, but the murder rate in Colombia (in South America) is a thousand times higher than the murder rate in Singapore. The murder rate in the US is five times the murder rate in Britain. Testosterone is the same here and there, but in Colombia there are drugs, gangs and weapons, there is poverty, unemployment, cruelty, and this puts part of the population, that is, men, at genetic risk. They have genes that put them at risk of murder if placed in a criminal environment. If you want to get rid of murders, you need to do what they did in Singapore and Britain – get rid of weapons. In these countries you can't get a gun: it's impossible. Singapore is trying to improve living conditions, reduce unemployment, and it's all working. So you can solve a genetic problem by changing the environment, and this is probably the most important thing you can tell the modern world about human genes.

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