Mirror for the brain
"In the world of science" No. 5-2008
Based on the materials of a conversation with the Doctor of Medical Sciences, corresponding member of the Russian Academy of Medical Sciences, Head of the Department of Systemogenesis of the Research Institute of Normal Physiology, Professor Konstantin Anokhin and Professor of St. Petersburg State University, Doctor of Philology and Biology, head of the Laboratory of Cognitive Research, neurolinguist Tatiana Chernihiv.
Why do we have a brain that sets us apart from all animals? What does the origin and evolution of the human mind look like in the light of the latest discoveries in this field? What explains the gap that exists between us and our "little brothers", from the point of view of modern evolutionary theory?
Where genes workIn 2003, one of the founders of Microsoft, Paul Allen, also known as one of the largest philanthropists, addressed scientists with the question: "What, with financial support, could science do today to figure out how the brain works?" He had very serious consultants – Nobel Prize laureates, people who stood at the foundations of modern molecular biology.
And they said that the main thing now is to understand how genes "make" the brain, i.e. to combine genome research and brain research and find out how many genes and which ones work in the brain, in which areas and how it happens. In other words, how the brain is genetically arranged is not only the most complex organ in humans, but also the most unsolved object in the universe.
Allen has allocated $100 million to make this task available. The Allen Brain Institute was established in Seattle, his hometown, where, by the way, Bill Gates is from. The Institute started working, and in January of this year a large article was published in the journal Nature on the results of this extremely effective project. In just three or four years, it was possible to map all the mouse genes and determine which of them work in the brain. A stunningly important result was obtained: it turned out that in the mouse genome, and, accordingly, in the human genome (the numbers will not differ much), more than 80% of all genes work for the brain. For comparison: in other bodies, these are units of percent. That is, in our genome, every eight out of ten genes work for the brain. This is the result of the accumulation of gigantic efforts of the genome in evolution to create a brain.
Now the same group of scientists from the Allen Institute is working on deciphering a complete map of gene expression in the human cerebral cortex. Knowing that the mouse and human genomes coincide by more than 90%, it is not difficult to predict the overall outcome of this work. However, it will certainly reveal many unexpected facts that are important for understanding the evolution of our brain and consciousness.
If we were to evaluate evolution as a set of small episodes, each of which, through natural selection, fixes the work of some gene for some functions in the body, it would turn out that genetic evolution was largely aimed at creating and maintaining the functions of the nervous system compared to other organs.
A very difficult question arises: which of these many genes working in the brain are responsible for our evolution? Can this be explained by one unique gene, which caused some kind of evolutionary explosion?
For example, according to the hypothesis of the famous American neuroanatomist and neuroscientist Pashko Rakich, a simple random mutational jump could be the basis of the emergence of the human brain, which is particularly different from the brain of other primates by the development of frontal sections associated with intelligence. It led to the fact that one of the genes associated with the cell cycle of the development of neurons in the cerebral cortex underwent small changes, and there were more division cycles. In the cerebral cortex of such a mutant, many more cells were formed than in relatives. This means that the functions performed by this area of the brain will be supported by a large number of cells, there will be more connections, more intellectual reserves. If the mutation occurred in the frontal lobe, then its carrier will have a lot of new opportunities to anticipate the situation.
And then behavior and selection suggested how to use these cells. Please note that evolution has not prepared such a mutant for anything yet. He just found himself in a situation where, with the same problems as his relatives, he has a greater resource of the number of neurons and possible calculations in this area of the brain. If this gives him advantages, and his gene is distributed in the population, then animals with the same large volume of the frontal parts of the brain will be born. Then, within the newly expanded area, those small mutations that prepare it for innate specialization in solving a certain problem will gradually gain advantages. This is the hypothesis of one gene that changed everything. But maybe it wasn't like that.
Animal – human: where is the border?First of all, we must determine for ourselves what exactly is so unique in a person, and this can be done in two aspects.
The first is morphological, or anatomical. If we think from this point of view, the answer is: our brain is three times larger than that of our closest biological relatives – chimpanzees, the cortex consists of layers, it is very complexly organized, etc. But if we think from the point of view of not just anatomy, but brain functions, it turns out that a person is distinguished from animals primarily by language. There is also the ability to perform calculations of various kinds, for example, those that allow predicting behavior, adequately assessing society, correctly imitating and creating something new, building a model of another person's consciousness. This requires a very complex brain.
The point is precisely in this, in the second part – in the functions. However, it is very difficult to determine which of them are purely human. As we study the organization of the brain and the abilities of animals, this "set" melts every year. For example, in serious textbooks it is written that the human language is a hierarchically organized system, i.e. there are phonemes – atoms or bricks, and there are a solid number of them in each of the languages. They are put into morphemes, morphemes are put into words, words into phrases, phrases into discourse... And supposedly (it has always been said so) we do not observe anything like this in the communication signals of other biological species. For example, most scientists claim that no one but a person is capable of thinking with such algorithms as recursive rules. But what about the birds that carry out very "advanced" navigation? After all, they have to calculate and navigate in a very complex space. Further, animals, especially of high rank, have an extremely multilevel society; even ants have incredibly complex organized communities. What can we say about monkeys, which it turned out to be possible to teach a human language? For example, their syntactic abilities are about the same as those of children two and a half years old. And this seriously changes the idea of our position on the planet: after all, until recently it was believed that such a thing was not available to primates, that it needed a human brain for this. Even the vranovs, whose brain is much less complicated, are able to do a lot, which gives reason to talk about the presence of reason. Singing and "talking" birds are capable of subtle and accurate imitation, which, by the way, is considered one of the main "human" qualities – at least, a person possesses it to a much greater extent than all other representatives of the animal world.
There are many more examples that suggest that there are fewer and fewer specifically human traits that we can hold on to, and which may have appeared as a result of a supposed mutation, this "big leap" from our biological ancestors to humans.
The second thing they always talk about is that human language has the property of productivity. This refers to the use of recursive, or symbolic rules: we can encode and decode an infinite number of messages built according to certain algorithms that are developed in our brain as a kind of "virtual textbook" of the first native language. And all this is available to a small child! If it weren't for some innate mechanisms that make it possible for everyone to master their first language in such a short time, it would take many decades! Hence the assumption, to which a large number of scientists are inclined, that it is necessary to look for a gene that determines the ability to speak.
And a few years ago, the well-known FOX2P gene was indeed discovered, the breakdown of which was found in families experiencing speech difficulties in several generations. However, this gene is not a "language gene". Almost every month we read about the discovery of new genes: the "memory gene", the "stupidity gene", the "reading gene", the "singing gene", etc. The question is not that these genes are not detected, but that the discoveries are misinterpreted. And so, returning to the question of human uniqueness, we first of all have to answer the question – is there this "gap" between us and our biological relatives, or is there not. A failure that gives reason to say that there was some kind of mutation that changed the brain so much that it became capable of language and other very complex algorithms, but in fact led to a much more complex organization.
Evolution of the mindSo, we must consider the scenario of how the brain could have arisen, which gave man the intelligence that we possess.
And here there are two serious alternatives. The first is that it happened as a result of a series of genetic changes that led to new modifications that could turn out to be "explosive". It's a series of mutations, a process. We are all talking about a kind of push, when one thing could happen that changed the properties of the brain, nervous system, and turned out to be evolutionarily adaptive. However, subsequently, many changes could be layered on this "explosive mutation", and what we see today is no longer the one mutation that we could possibly find, but thousands that lined up along it.
This is scenario number one, and it is being considered very seriously.
But there is another one, according to which it all started with some modifications of adaptability, plasticity of the brain, which, falling into a slightly different evolutionary niche, began to realize new possibilities. If this happened under changed conditions in a number of generations, then genetic variations could begin to accumulate, making development in this direction more and more easy. Accumulating, such variations led to the formation of the human brain in its current form. Such a scenario excludes the presence of the initial "key gene" that caused the push.
If we can call the first scenario "genetic", since genetic changes lie at the beginning of the process, then the second is epigenetic. By the way, many geneticists and evolutionists are increasingly beginning to consider it as an evolution scenario. These theories were one of the first in the world to be developed by the remarkable Russian evolutionist I.I. Schmalhausen, who said that evolution does not begin at all with changes in the genotype, but on the contrary, it is a change in the phenotype, which is gradually fixed, formalized into a change in the genotype.
What do the experimental data say about these two scenarios? In August of the year before last, the results of a study were published, which consisted in comparing the genomes of humans and chimpanzees. Scientists have been trying to find areas of DNA where strong changes have occurred over 5 million years, which separate us from chimpanzees. And there were 49 sites where the rate of change was significantly higher than the average for the genome. Moreover, on some of them, changes occurred 70 times faster than the average genome!
The sites are scattered throughout the genome, and then the question arose: what functions do they perform? As a result of detailed studies, the gene that has undergone the most significant changes has been isolated. This is the HAR1 gene encoding a small section, a small RNA, but it contained 118 (!) differences between humans and chimpanzees. And there were only two discrepancies between, for example, chimpanzees and birds (chicken).
This gene has been around for a long time. Birds and mammals have it, but it was on the way from chimpanzees to humans that the most changes occurred in it.
Then the experts asked the question: what are the functions of this gene? And it turned out that this is a gene that works in the cerebral cortex from the seventh to the nineteenth week of embryo development, when the upper layers of the cerebral cortex are laid, defining horizontal connections. It has always been believed that these are the most recently emerged evolutionary layers that greatly distinguish the human cerebral cortex from the brains of other primates. It turned out that this gene is somehow (it is not yet fully clear how) connected with the regulation of the work of other genes. It encodes a short regulatory RNA molecule that can regulate the work of others.
So, today it has already been proven that there are areas that distinguish the human genome from the chimpanzee genome by the highest rates of evolution. And the fastest in the evolving structures turned out to be the site that is associated with the work of a gene in the cerebral cortex (and not just in the brain) and with the development of this brain and those areas that can distinguish really late stages of evolution, different in humans and chimpanzees. The functions of this gene originated a very long time ago, which, by the way, is a very strong argument against any simplifications, such as, for example, with the discovery of the same "language gene". They started talking about it only when it was discovered in humans, but it turned out that mice, birds, and worse, crocodiles have it!
In general, it seems that the whole evolution is aimed at the neuropath, at the development of the brain. This could be caused by the fact that the environment required a load on the nervous system. Mutations occur in all genes responsible for certain functions in different organs, not only in the brain. It's just that natural selection puts a greater burden (from the point of view of adaptation) on those functions that are related to behavior – there is more serious pressure, there is a more active accumulation of adaptive mutations.
The nervous system "pushes" us into such conditions (and allows us to adapt to them), which entail the appearance of new morphological features. For example, if a change in behavior leads to a change in the types of food, then the structure of the body gradually changes, etc. That is, the brain can also accelerate morphological evolution.
So, one of the brain structures suddenly begins to become more complicated as a result of certain genetic changes that can accumulate due to the fact that the organism, the population got into other conditions, where their plastic brain then begins to lead the evolution of the genome. This is exactly the second, epigenetic, scenario.
An interesting parallel comes to mind here from the famous book by Terrence Deacon, Professor of Anthropology at the University of California, "Symbolic View". He writes there that it is not the language that has adapted to the brain, but on the contrary, the brain has adapted to the language. Deacon's book is, in particular, one of the first statements of the hypothesis that it was not genetic changes (even if we see them today) that underlay the appearance of language, but vice versa. It seems that in general, in the process of evolution, it is often very difficult to separate cause from effect, because we are talking about the evolution of a system that moves multidimensional. But, on the other hand, there was an objective reality, and we want to know it. It cannot be both at the same time – these are two different paradigms. Maybe in some situations some principles work more, in others - others.
But one thing we can say for sure, based on recent research: any non-evolutionary scenarios of the appearance of man and the human mind on the array of data that we have today are simply not realistic. After all, the answer must be sought within the framework of a modern, synthetic theory of evolution. And secondly: the number of similarities at the genetic, morphological, functional level, when the boundaries between properties unique to humans and other animals disappear, is such today that the mystery of the human brain and mind becomes the main one in the XXI century. This riddle will probably be one of the main ones in science, but it must have an evolutionary solution.
Memory – internal and externalIn addition to the brain itself, the mind, a person is distinguished from other animals by another unique property, namely, the so–called remote memory, the ability to carry accumulated knowledge beyond the limits of the individual brain.
It is thanks to this that cultural and social evolution has taken place, which is proceeding at an incredible pace and has led to a significant change in the number of mankind. After all, if measured on a biological scale, then our cultural evolution takes an insignificant amount of time, some millisecond - and at the same time such amazing efficiency! This process goes beyond traditional genetic selection, which fixes hereditary traits in generations.
This is also due to the fact that our brain is extremely plastic. And every next generation, being born, interacts not only with their parents, but also with society, with accumulated external memory, history, experience and is ready to assimilate all this thanks to the plasticity of the brain. And here it would be appropriate to go back to the so-called "language gene". We touched on two questions: firstly, was there some kind of push that led to the emergence of language, and was it related to the gene, and secondly, if so, whether the language? Why, say, not memory? When studying the function of this gene, it turned out that certain forms of memory – namely, the so-called "working memory" - were damaged in patients suffering from speech disorders. This is the retention in memory of operational information, events that have just occurred, goals and motives for actions – i.e. things that depend on the anterior parts of the brain, on the frontal lobes associated with goal-setting and probabilistic forecasting.
How does this system work, which controls, in particular, language as one of the most important manifestations of consciousness? Both memory and the picture of the world that surrounds you appear there, and, most importantly, how you contact it, use external memory and put your own information and your own feelings into this memory. What is called social consciousness as the fruit of human consciousness. And here we should warn against simple solutions – that all this arose as a result of single genetic changes, or that individual genes are at the heart of these complex processes. The fact that defects in some gene can selectively lead to a violation of speech, understanding, language acquisition, does not mean anything yet. Take a simple mechanical system, such as a tree with many roots and a crown. If you cut one of the roots, you can see how some of the branches are drying. But will this mean that these branches grew from exactly the same root?
Did the HAR1 gene lead to the miracle that we face when we see how a small child manages to master his first language? This is an amazing thing, because no one ever teaches him! The baby does not know in which language environment he will be born: in Japanese, in Moldovan, in Russian or another. It does have genetic mechanisms, but the awareness of the need for the existence of these mechanisms and the expectation of the discovery of one responsible gene separates a large space. Definitely, the brain has the ability to "write" the algorithm of a given language. After all, the child's brain must create a kind of "virtual textbook", and independently, since no one ever explains anything to him. How does he manage to do this – with all the structure, all the recursive rules, grammar, emotional connotations – and even in the shortest time, i.e. by the age of three, although there is a huge period of evolution behind this?
Interestingly, there is control over the expression of genes that have already done their job when a person was little and his brain was just forming, and then these genes should be silenced because they played their role. But depending on certain conditions, the genes can start working again, already in adulthood. Like Baron Munchausen, we pull ourselves out of the swamp by the hair in the sense that our brain is an organ in which development never stops. What we encounter through our experience constantly provokes changes in the work of genes and small episodes of morphogenesis that develop our brain. Cognitive processes stimulate genetic processes – a completely unexpected and simply amazing fact! But there is nothing like Lysenkoism here, although some use the metaphor of "social (cultural) inheritance."
The neural network becomes more complicated depending on what the brain is doing – this has been known for a long time. Naturally, new more complex connections are formed, and there are no miracles here. But the fact that genes are involved in this process still has a novelty, although there is nothing strange here, if we think from the standpoint of cell biology. And, nevertheless, it sounds very optimistic and in some sense moralizing: a person must constantly remember that the fate of the brain depends on what his brain is doing.
Conceptual bridgeSumming up, we can say that we touched on different levels of origin, development and work of the brain and consciousness, but the riddle of the mind will be solved only when we consistently go through them all.
In many ways, the features of the human mind depend on the functional anatomy of the brain, but this anatomy was created gradually, and we need to understand the laws of brain development, the laws of evolution related to genes, we need to build a continuous conceptual (not simplistic) bridge that will help reproduce a single picture. It is no accident, therefore, that many outstanding scientists say that in the XXI century the problems of the biology of the mind and the biology of the brain will take the place that in the XX century the problems of the biology of the gene and the biology of heredity occupied.
For beings of the human type, such a possibility of processing information is characteristic, so if we want to know anything about the world at all, we must first find out how the brain and consciousness function by which we know it.
One English encyclopedia says that consciousness is the most obvious and least understandable thing in the activity of the human brain. We all understand this, but still we are not trying to define it yet. We tried to look beyond this boundary, using modern advances in genetics, psychoneurolinguistics and understand how our consciousness works, how language works, and how we understand ourselves and others. This is, in fact, the most interesting thing in a person – the self-knowledge of our mind.
Prepared by E.V. KokurinaEditorial office "In the world of science"
expresses gratitude to the program "OBVIOUS – INCREDIBLE" for the help in preparing the material.
Portal "Eternal youth" www.vechnayamolodost.ru16.05.2008