Cryopreservation via a cryonics provider, such as Alcor or the Cryonics Institute in the US, is presently the only option available to the billions who will age to death prior to the advent of a comprehensive package of rejuvenation therapies. Sadly, it is not yet a well-developed industry, operating at scale. The technology exists to vitrify people immediately following clinical death, preserving the fine structure of brain tissue if the vitrification process is of sufficiently high quality, but very few people choose to take advantage of this opportunity. Every year, tens of millions go to oblivion rather than chose the better option. Given preservation, there is the chance of restoration to life in a more technologically advanced future. The odds of success are unknown, but any chance is better than the certain oblivion of any other end of life choice. The cost of cryopreservation is small, provided that preparations are made decades in advance, as it can be funded via life insurance.
The popular science article noted here presents an array of comments from people for and against cryonics as an endeavor, and captures most of the important divisions. There is the disagreement over whether sufficiently well performed vitrification can preserve the structures that encode the mind, which seems to me to be the case, given the evidence from experiments in nematodes. There is the debate over whether present practices actually constitute sufficiently well performed vitrification. Then there are those who think it is better to go to oblivion than to be restored in a new era, which I can't say I agree with at all. Finally there are those who will never be convinced by any amount of indirect evidence, such as the nematodes or reversible vitrification of whole organs for use in the transplant industry, and will be skeptics until the day that someone is restored to life.
As is the usual case in the popular press, the article title and commentary willfully substitutes "frozen" for "vitrified". These are two very different things. Only the earliest of the preserved individuals were frozen, and we can be rightfully skeptical that there is anything left to restore there. Freezing produces ice crystals that shred cell structures, such as the synapses where it is thought that memory is encoded. Vitrification, on the other hand, involves the use of cryoprotectants that minimize ice crystal formation, turning tissue into a glass-like state. Reversing this process will require advanced nanotechnologies, of a sort that can be envisaged today but will only arise many decades in the future at our current pace of development. For so long as the structure is preserved, then reversal remains a possibility, only waiting on the technical capability to do so.
Dr. Joao Pedro de Magalhaes, Biologist at the University of Liverpool and coordinator of the UK Cryonics and Cryopreservation Research Network
I'd say that with today's technology, cryonics severely damages the body's cells. Even under optimal conditions (i.e., the procedure starts right after death), there are several problems in cryonics. In particular, cryoprotectant agents have toxic effects on human tissues with prolonged exposure. Vitrifying large organs like the brain can also result in fractures due to different cooling rates in different parts. Under non-optimal conditions (i.e., if a significant time elapses between death and being cryopreserved) much more damage can occur because cells start to die, and brain cells in particular start to die within minutes after cardiac arrest, due to lack of nutrients and oxygen (called ischemia). Therefore, it will take huge scientific advances in areas like tissue engineering and regenerative medicine to make cryopreserved individuals alive and healthy again. As such, I would say that the chances of cryopreserved individuals ever be revived is low but not impossible. And then the argument is that the worse possible outcome of being cryopreserved is to remain dead, so cryonics gives you a chance of future revival that will not happen if you are buried or cremated.
Mark Kline, Co-Founder and CTO, X-Therma Inc., a company improving cold storage of stem cells, tissues, and whole organs
The hardest thing to solve is: how do you freeze things without damaging them? You mix in all these cryoprotectants - like antifreeze for your car, but geared towards biology - in an effort to prevent ice formation within the cells and tissues. But you need to drastically lower the temperature - down to about -196 degrees C, liquid nitrogen temperature. Preventing ice formation at that temperature, throughout a very large tissue, is very, very difficult. So there's the chemistry problem (preventing ice), the biology problem (tissue damage, connection damage), the physics problem (how do you evenly cool something as large as an organ? And how do you warm it up evenly afterwards, without damaging it?). I think there are much more imminent applications for cryopreservation, like organ preservation. Preserving organs has a high-value impact for the medical system, and also is much more feasible than preserving a whole body. You can save many, many lives with organ preservation.
Nick Bostrom, Professor at the University of Oxford and Director at the Future of Humanity Institute and the Governance of AI program
Technically it seems like it should probably work. The freezing (rather: vitrification or plastination) and storing we can do now. The bringing back part may however require the assistance of machine superintelligence in order to repair the extensive cellular damage that occurs during the suspension process.
Dennis Kowalski, President, Cryonics Institute
The scientifically correct answer is that we do not know, since no one knows the future and what will be possible. However, that is why some people have signed up to preserve their bodies at liquid nitrogen temperatures in hopes that future technology and medicine will be able to answer that very question. New technologies moving forward might mean advanced, AI-guided stem cell therapies that regenerate tissues that have been damaged by aging, freezing, or death itself. Technologically we are advancing at an exponential pace, and this means that things considered impossible even a few decades ago will become reality.
Cathal O'Connell, Researcher in 3D bioprinting and biofabrication at BioFab3D, St Vincent's Hospital, Melbourne
All signs point to no. The freezing-down process is critical. Doing this in a way that preserves cell function - especially regarding connectivity in the human brain - is way beyond our current capabilities. Unfortunately, everyone who has ever been frozen so far is essentially turned to mush. These people will never be revived. Cryonics in its current form is more of a religion than a science. Rather than a divine entity, its followers place their faith in technological progress. The ability of some organisms to survive freezing is a sign from nature that what cryonics promises might one day be possible. But getting there will require a massive investment - billions of dollars, thousands of scientists, decades of research. Without a clear economic incentive, that investment is not forthcoming. As my old professor says, a vision without funding is hallucination.
Ralph Merkle, Director of Alcor Life Extension Foundation, the world's leading cryonics organization
The short version is: many of the patients at Alcor will likely be revived sometime this century. Had you asked a random person in 1940 if flight to the moon was possible, you'd likely have been told "no." If asked why, a typical answer was "because there's no air to push against in space." This scientific-sounding but totally false objection was infamous among knowledgeable scientists, and was the basis for the New York Times' 1920 editorial denouncing Robert Goddard. Yet those knowledgeable about space flight had been forecasting flight to the moon for decades before the event. Similarly, those knowledgeable about nanomedicine have also been forecasting the revival of cryopreserved patients for decades, and those forecasts are likewise based on a sound assessment of physical law. Until the structures in the brain that encode our memories and personality have been so obliterated that they cannot in principle be inferred and restored to a functional state, you are not dead. This information theoretic criterion of death is obviously much more difficult to meet than current legal or medical definitions, hence the belief that cryopreserved patients are not actually dead.
Michael Hendricks, Canada Research Chair in Neurobiology and Behaviour and Assistant Professor of Biology at McGill University and wrote "The False Science of Cryogenics" for the MIT Technology Review
If you mean people who have already had their brains, heads, or bodies cryogenically stored after death (or are doing so with current technology): no, they will never be revived. They are dead, and will remain dead forever. Will it ever be possible to store a dead person (or a dead person's brain) in such a way that they can be revived? Almost certainly not. Look at the world. The only good thing we still reliably do for future generations is get out of their way. Let's not take that away from them too... they will have their hands full with all the horrific problems we've left them because of our selfishness and greed. We shouldn't making them responsible for keeping our bodies cold, too.