New York University scientist Sam Parnia claims that under certain conditions it is supposedly possible to bring the dead back to life. Such statements always cause a wide resonance. Are there real scientific prerequisites today to talk about the irreversibility of death?
First of all, I will explain that there are two types of death — clinical and biological. In the first case, life processes stop, which leads to the destruction of the cellular structure in organs and tissues. Destruction in each organ occurs at a different rate. The brain is the least able to cope without oxygen and nutrients. Some tissues, such as bones, can survive for several days in a state that allows them to be brought back to life.
In fact, it is due to this difference in the rate of tissue decay that transplantology is possible, since after brain death most organs are still intact and can be transplanted to another person. Cryopreservation also allows for this state of organs to be prolonged until transplantation.
What Parnia is talking about, of course, so far sounds more like science fiction.
How does the transition of a living cell into a non-living state occur at the molecular level? Can frozen embryos, for example, be considered non-living? After all, they are capable of returning to an active state later...
Embryos are not yet an organism, but only a few cells. As part of the in vitro fertilization (IVF) procedure, embryos are indeed subjected to cryopreservation in liquid nitrogen for a time. Like sex cells, gametes, embryos can tolerate freezing, thanks to which many reproductive technologies are now being developed.
When the idea of reviving dead people or animals is discussed, cryopreservation is also usually discussed. However, these are complex multicellular organisms, not individual cells. Between the cells in the tissues there is intercellular fluid, which will change its volume during freezing and defrosting, which will damage the cells themselves. Therefore, even those scientists who are working on the topic of cryopreservation of people say that it will take several months to defrost the preserved bodies.
But this is all just a theory, because so far there has not been a single case of reviving a defrosted human or other mammal in the world. And the main problem is precisely the impossibility of ensuring the complete preservation of the structure of tissue and organ cells, primarily the brain.
According to one theory, nanorobots will help solve this problem - special molecular 'machines' with which it will be possible to 'repair' all cellular damage. But at the moment this is very far from implementation, only ideas. Such technologies have not been tested even on laboratory animals, let alone humans.
So far, the maximum is experiments on individual cells, but, as I said earlier, a cell is not the same as a whole organism, or even an organ. And even if we learn to prolong life or return individual organs and tissues to it, it is unlikely that this will help to “reassemble” a person from them, because an organism is not a Lego constructor.
It is known that amphibians can return to life even after freezing, this largely inspires supporters of the ideas of cryopreservation of people. Do we understand correctly that in this case we are not talking about reviving a dead creature, but about exiting suspended animation?
Yes, the anabiosis that frogs fall into when the temperature drops is not death, but a special condition in which organs, systems and tissues stop functioning, and hibernation begins. All processes in the body slow down or stop. But since this is not death, the structure of tissues and organs is not damaged.
What exactly happens in the brain during the dying process? What exactly is destroyed the fastest? And why is this particular organ so vulnerable?
It is precisely because of the vulnerability of the brain that people so rarely come out of a deep coma and return to normal life; this is a very small percentage of the total number of cases. The fact is that the work of our brain is provided by neural connections. When oxygen stops flowing into the brain cells, rapid destruction of not only neurons but also the connections between them begins. The cerebral cortex, which is key to thought processes, is located farthest from the large arteries that feed the brain, and therefore it suffers first. This further aggravates the situation. Thus, even if a person suddenly survives after defrosting as a result of cryopreservation, or is preserved in some other way, he will wake up as a “vegetable”, will be in a vegetative state with a very high probability.
The reasons for this are explained by molecular biology. Each cell contains organelles called mitochondria, which are busy producing energy, and they are very sensitive to lack of oxygen. When the mitochondria stop working, the cell cannot function and begins to deteriorate.
The rate of cell destruction depends on the density of the tissue. For example, bones, as I have already said, can last for several days. They have a higher margin of safety, their cells do not urgently need a constant supply of oxygen. The softer the cellular structure, the more vulnerable it is in this regard, in the case of the brain, every minute counts. And this is the main problem for doctors and resuscitators.
Parnia cites the results of a study by Yale scientists who in 2019 managed to restore the brain function of a pig four hours after its death. However, the authors of the study themselves note that, although the pig’s brain formally began to be supplied with blood, “came to life,” electrical activity, that is, the work of neurons, did not resume. So, this is equivalent to being in a completely unconscious state?
Yes, in essence, these researchers managed to prevent biological death, but not clinical death. This is not some kind of huge scientific breakthrough, because, unfortunately, patients falling into such a vegetative state after severe injuries or poisoning is not uncommon in medicine. For example, it happens that after a stroke, some parts of the human brain are preserved, but, in fact, it can no longer function normally. Here it would not be superfluous to recall how important it is to protect the brain from injuries, unfavorable factors, oxygen and nutrient deficiency. This is the most complex organized structure in our body, it has not even been fully studied.
Is that why transplanting a new body to a head is not yet possible? After all, the Italian surgeon Sergio Canavero never actually performed a human body transplant, although his bold announcements attracted a lot of media attention at the time — as do all such promises by scientists.
Yes, the difficulty is that such an operation cannot be performed instantly, within a couple of minutes. And this means that the brain will suffer while a new body is being sewn onto the patient's head.
Most often, the search for solutions to revive the dead is discussed in the context of discussions about currently incurable diseases. People hope that after defrosting and reviving in a few decades, they will, for example, be able to cure these ailments, because science will have made great strides by that time.
But it is not yet known how organs affected by disease will tolerate such preservation, in the case of the brain, this is, of course, primarily Alzheimer's syndrome and oncology. In this regard, the ideas of transhumanists who dream of transferring the human connectome, that is, the totality of neural connections, consciousness, to some non-biological carrier, such as a processor, are even more interesting. But, by and large, all this is just science fiction for now.
In any case, life has a finite duration, so such technologies, if they are ever created, will be able to help those who have fallen ill with some incurable disease at a young age or have been injured. And even then, if science has not learned to solve these problems by that time, and there will be hope that it will be able to do so in some distant future. Especially since a young organism is more likely to be able to withstand such manipulations to revive, etc.
In fact, thanks to advances in medicine, we already live on average twice as long as our relatively recent ancestors. This is already quite a sufficient reason for joy - today's 80-year-old people live, in essence, another life that our great-great-grandmothers and great-great-grandfathers did not have.
