Eternal life? Don't get your hopes up!
Why are we all going to die
Several recent scientific publications
greatly undermine our hopes for eternal lifeAlexey Aleksenko, "Snob"
There is an opinion that to live forever, well, or at least longer, is the main interest of mankind throughout its conscious history. This opinion is complete nonsense, of course.
Interest in the problems of longevity briefly captured the minds of people exclusively in relatively prosperous, sluggish epochs that did not promise imminent cataclysms. For example, at the very beginning of the twentieth century (the well–known "Madam, I will transplant your monkey ovaries!" by Professor Preobrazhensky is a distant echo of those scientific daring). Another peak is the end of the 60s, and the last explosion of interest in life extension falls at the end of the 90s, when the half–crazed freak Aubrey de Grey said: "The first person who will live to be a thousand years old has already been born, and now he must be fifty years old."
On the contrary, there are such historical epochs when talking about longevity means gaining a reputation as a cheerful idiot. I'm not sure if we're living in one of them now, because it's not always noticeable from the inside of history. For example, Ivan Mechnikov made a mistake at the time: he decided that it was time to extend his life to a hundred years with the help of a special Mechnikov curdled milk, but then Leo Tolstoy, already then the "mirror of the Russian revolution", ridiculed him maliciously and maliciously, anticipating the coming changes.
Nevertheless, let us be filled with benevolence and talk about the long life that the editorial board of "Snob" wishes to all readers, even if contrary to scientific forecasts. A couple of recent scientific studies give us, if not a reason for optimism, then at least a topic for conversation.
Until recently, one could hear the following argument proving the inevitability of prolongation of life, if not immortality. Look here. Now, every five years, the average life expectancy of a person on Earth increases by two years (and forty years ago it increased by one year in five years). That is, scientists strained a little, and life expectancy began to grow faster.
And this means that if scientists try a little more, it may turn out that every five years the average life expectancy will increase by five years.
That is, now I can statistically expect to live another thirty years, and five years later – again thirty, and so on indefinitely. And that means what? That people "on average" will become immortal.
Probably, it is not even necessary to explain where the rat is hiding here. It lies in the fact that in fact the life expectancy of a person has practically not changed for the last hundred thousand years. For example, the biblical "The days of our years are 70 years, and with a greater fortress of 80 years" is quite relevant to this day (well, maybe now in developed countries a little more, but this is not at all the staggering growth rate that was briefly observed in the second half of the twentieth century).
A curious review in Scientific American (Why Humans Live So Long) provides interesting data on life expectancy in primitive communities (both ancient, according to the results of the study of mummies, and preserved to this day). Yes, life expectancy at birth barely reached thirty years, but if a person lived to puberty, he had another forty years left. At the same time, octogenarians were not uncommon at all. So where is your progress?
This observation has actually been going on for thirty years, but the article goes a little further, posing the question: if a longer human life compared to, say, a chimpanzee is the result of a single mutation, then what kind of mutation is this, what kind of gene? It turns out that there are already specific suspects – for example, the APOE gene, which affects, in particular, the intensity of the inflammatory response to infection. The authors argue in favor of the fact that this gene was subject to strong selection pressure, and this is due to the exit of human ancestors from the forests to the savannah and the transition to animal food.
And here we should have a question if we are thinking at least a little, and not just sitting in front of the monitor. Why, in fact, has the human life expectancy gene become susceptible to positive selection precisely in connection with meat-eating? Common sense suggests that a gene that brings individuals even a couple of extra years of full life will allow them to leave more descendants, and therefore should ALWAYS be supported by selection. Is not it so?
And why then, after a billion years of evolution, does all living things still age and die? Why did life need death? If some mad scientist hopes to get immortality for people without knowing the answer to this question, he is really mad. And no one knows the answer, as luck would have it.
Nick Lane in his wonderful book Life Ascending gives a curious fact. In all animals that geneticists are currently working with, from the C. elegans worm to mice and flies, it is quite easy to get mutations that noticeably lengthen life. Mutations that shorten life (apart from some severe genetic diseases that greatly reduce fitness) are practically unknown. It seems that nature has always refused the possibility of a long life for its creatures, by default setting the timer to a minimum. How this mechanism is supported by selection is completely unclear. But, apparently, it is supported, or then God punished us for something.
A very similar picture, by the way, is observed with sex. From the point of view of selection, sex is a property of organisms when not one, but two are needed for procreation. That is, the efficiency of gene transfer to descendants is exactly twice as low as with immaculate conception. And yet the immaculate conception is an unprecedented miracle. And even worse: almost all kinds of organisms that are capable of this (like, for example, dandelion) are very evolutionarily young. And this means that a species without sex does not seem to live long. It is dying out for reasons that are not yet fully understood.
Maybe it's the same story with death. And this means that humanity, a very young species that received the cherished mutation of longevity a million years ago by the will of fate, is also doomed. For some reason that is still unclear. And to deal with this is probably even more important than prolonging our lives for another couple of hundred years, not to mention eternity.
Thus, scientists have not even decided yet whether we live too little or too much for our own good – what can we expect from them.
One of the attempts to understand this issue was recently reported by the journal Nature (Diversity of aging across the tree of life, see "Aging options: a slice of the evolutionary tree" – VM). But instead of clarifying the question "Why is death necessary?", the article by Danish biologists only confused everything even more. These pesky guys tried to find out how mortality varies with age in different species and how it depends on the duration of the reproductive period.
Answer: it does not depend in any way. For people in developed countries, for example, the probability of death begins to grow very slowly shortly after birth, and then, decades after your last children are born, it soars sharply. This rise, in fact, we call "death from old age", and gerontologists – "J-shaped curve".
But most species of living beings do not have anything like this. For example, in hermit cancer, the probability of death does not depend on age at all. And in tits and some lizards, it grows slightly with age, but without any hint of this sharp rise at the end, which, in fact, constitutes such a painful existential problem for a reasonable person.
Worse: turtles and oaks have a lower probability of death with age. In other words, the longer you live, the longer you can expect to live. If you are afraid to remain a widow, girls, marry Mr. Dolgikh, a ninety-year-old member of the Federation Council of the Russian Federation from Moscow: there is a high probability that he will even survive Putin, not to mention you and me. That is, it's not real, but if he was an oak or a turtle.
Of course, all this does not cancel out the pessimistic reasoning from Nick Lane's book: perhaps nature does not bother with a special "mechanism of death" in cases when representatives of the species are already effectively dying from accidental causes. The question of why natural selection does not support a constant, from generation to generation, increase in longevity in all its creations has remained unanswered.
And another myth about old age has been shaken as a result of a recent study. American neurophysiologists decided to check whether the human brain really deteriorates so terribly and irreversibly with age that it would be simply inhumane to prolong this farce. And it turned out that it does not deteriorate at all, but even improves.
They investigated functional connections between different parts of the brain. And they found that they really change with age, but they change not just "for the worse", but very sophisticated and purposeful, with a noticeable complication of some networks. In order not to bore the reader with clever names of different parts of the brain, let's just say that the result of such changes could be an acceleration of information processing and an increase in "life satisfaction" (psychologists have long noticed that old people, paradoxically, despite the proximity of death and the likelihood of illness, rarely soar over trifles, and now it becomes clear that this the process is programmed in the development of brain structures).
Thus, we get better with age, and then we die for something. And we have such a question for scientists: "Is this really necessary for some reason?" But scientists cannot yet give a negative answer to it, which we expect so much from them that sometimes we even see it from scratch.
Because, it seems, you still need to. However, we will follow the further development of the plot – while we are alive, of course.
Portal "Eternal youth" http://vechnayamolodost.ru20.01.2014