Maybe some of those who have read the fragments I presented from my new book “Origin of the mind; From viruses to beliefs” asked themselves why I choose this title? In this last part I will answer to this hypothetical question.
The human body has two immune systems: innate and adaptive (or acquired). Innate immunity refers to an unspecific defense mechanism which is mobilized immediately or several hours after exposure to microbes. Humans are born with this type of immunity. It is the initial response of the organism, targeting microbe elimination and prevention of infections. Within the adaptive immune sustem, there are only some lymphocite B and T that recognize each form of microbe. These cells need to multiply rapidly in order to produce enough cells to generate an efficient immune response against a certain microbe. This process involves several days. In the meanwhile, the microbe may produce considerable harm, and as a consequence, the innate immune system plays a fundamental role. The adaptive immune system is activated by the older, non-specific innate immune system, which represents the main protection system against pathogens in all being. Subsequently, adaptive immunity is elicited when a pathogen surpasses the innate immune system and generates a certain threshold level of antigens. The adaptive immune system has the ability to memorize and recognize specific pathogens (to generate immunity), and to launch attacks each time that specific pathogen is encountered. This is called adaptive immunity because the organism’s immune system prepares for subsequent challenges, as opposed to the innate system.
The adaptive immune system appeared in the first vertebrates with jaws (jaw-fish), 450 million years ago, and evolved in a time interval spreading over a little less than 20 million years. Genetic analyses have shown that the occurrence of the adaptive immune system was preceded by the double duplication of the genome, which is responsible for the genes of the adaptive immune system. Gene duplication plays an important evolutionary role considering that one of the new copies may have a new function. Genetic studies indicated that the majority of genes in the adaptive immune system resulted from the primitive nervous system found in vertebrates, and by virtue of their duplication, they gained a new function. Genome duplication and gene diversification, which occurred 550 million years ago, before the development of the adaptive immune system, is regarded as a possible mechanism underlying the evolution of the vertebrate brain. There is an abundance of evidence demonstrating that the adaptive immune system resulted from the action of retroviruses (a retrovirus is a virus which succeded in inserting into the DNA of the host and in this way is transmitted from parrents to offspings).
The immune and nervous systems are traditionally believed to serve different functions. Nonetheless, the differentiating line between the two becomes more and more flimsy. According to genetic data, it seems that the brain evolved from molecules derived from retroviruses that have lost their initial function, and were instead co-opted to create genetic diversity and aid genome expansion – a process known as exaptation. L1 retrotransposons (retrotransposons are mobile elements from the genome which are actually fragments of ancient viruses) are considered to be the most creative force participating in the construction of genomes throughout evolution. L1 elements are to a greater extent cognate to the elements from the introns in mitochondria and eubacteria. L1-produced retrotranscription is extremely old, and that is why its generating elements may be regarded as relicts of the first systems associated with life self-replication, presumably reaching back to the “RNA world” assumed to have preceded the current “DNA world”. It seems that L1 helped the development of a brain capable to process information about rapid environmental modifications, thus facilitating increased adaptability to climate changes and any other sort of changes.
Humans and their ancestors have been permanently under the attack of viral parasites and other forms of invaders that expanded the human genome using “jumping DNA”. Their organisms were not capable to completely eliminate these invaders. Instead, they had to adapt, and in order to coexist, they silenced these invaders by means of various intelligent mechanisms, which determines their mutations in order to deactivate them. Recent studies found that L1 elements are 100 times more numerous in the adult human brain, compared to the heart, skin or liver. Most of them were found in the hippocampus and frontal cortex, thus reflecting the great contribution of newborn neurons that develop from stem cells, in these areas of the brain. L1 elements produce a specific enzyme that “writes memories”, and not just genetic memory, but immune memory and memories in the brain as well. So it seems that our memories are written by the same mechanisms that control the immune system and these mechanisms have viral origins. And many experimental data support this hypothesis showing the string connections between the nervous and immune system and also the similarities in their functioning.
Various experimental studies discovered that perception of danger threatening our social connections seems to be processed by the same neuronal network that responds to physical threat. And these structures are associated with a more general stress/anxiety system activated by any type of negative events, thus generating inflammatory responses. The neuronal mechanisms responsible for generating defensive reactions such as anger or anxiety are coupled with the immune system, which is traditionally regarded as a defender of the organism against non-Self agents or antigens. Considering these origins, the nervous and immune systems hold functional similarities. One of them refers to the process of generating novel neurons and synapses, which are maintained consequently to exposure to information during a sensitive or critical period, similarly to the process underlying T and B lymphocytes in the adaptive immune system.
It seems that the nervous system, akin to the immune system, underlies a selection in terms of identity and neuronal connectivity occurring both throughout development and during processes associated learning. Once the neurons are “marked” with a certain category of information that particular neurons become dependent upon that information. Any kind of information, from parents to culture. Subsequently, they will attempt to update and defend that information every time they get the chance, thus preventing its “dislocation” by other pieces of information (or cognitive immunity). This mechanism is similar to the one responsible with creating addiction modules, which were initially genetic. Addiction modules reflect the impact drugs have upon our brain, so is a chemical addiction. But more advanced organisms added what we call, learning. Learning mark the genes from our neurons and implement the “addiction modules” in these neurons. Life experiences are reflected in the brain in the form of the “Self”, similarly to the immune Self, while the nervous system defends this construction in the same way the immune system defends the organism against microbes or viruses. This is why we tend to search for our favorite things in life and to protect our beliefs in face of challenges – like incongruent information. So we are addicted to our beliefs and our habits because information we learn takes control over the genes of our neurons and become resistant to displacement in the same way a virus protect himself.
Given that almost half of the human genes are produced by retroviruses and the learning machine that generates values and beliefs has its origin in ancient viruses we can conclude that humans, among other beings, are the constructions of viruses and the information infects us like a virus infects a species.