Perhaps inevitably in such turbulent, uncertain times, there’s a renewed interest in cryonics: the freezing and storing of human remains so that they can be resurrected in the future when medical technology is sufficiently advanced.
The appeal of this is obvious. It’s basically the mortality equivalent of a video game save point, allowing you to ‘undo’ whatever life-ending harm you’ve experienced and pick up where you left off.
But a growing enthusiasm for cryonics doesn’t change the fact that, at present, it’s a process with many significant hurdles to overcome before it could be said to ‘work’, in any meaningful way.
Freezing is fatal
Cryogenically freezing someone is rarely, if ever, permitted before that person has died. Why? Because freezing a living body is inherently a lethal process and, even if they’re okay with it, it’s illegal to kill a person.
It’s often said that the human body is mostly water. Water makes up the bulk of the vital fluids that keep our cells and tissues alive and functional.
When you freeze water, however, it turns to ice. Solid, expansive, spiky ice. If living cells are suddenly filled with it, ice does a lot of damage. This is why freezing and thawing things like strawberries renders them mushy – the cells that give strawberry flesh its structure are badly disrupted.
And that’s a piece of fruit. A human body is far more complex, sustained by countless different tissues and delicate biochemical processes.
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There are ways around this. The speed of freezing can reduce the presence of ice crystals, as can the inclusion of cryoprotectants (chemicals that prevent or reduce the cellular damage done by freezing).
While such approaches can work for individual cells or tissue samples such as embryos, the more cryoprotectants are needed, the more toxic they become to the delicate chemical processes that sustain life. So, the larger and more complex an organism is, the harder it is to freeze ‘safely’.
More importantly, no sufficiently complex living organism is ever fully inert. It’s always biologically active, being sustained by innumerable biochemical processes. Freezing shuts these down. Turning them back on again isn’t like flicking a switch on a machine, but more like trying to unscramble an egg. While not impossible with sufficiently advanced technology, it’s certainly not easy.
The delicate brain
Many prospective ‘cryonauts’ freeze only their head or brain. Presumably because, if medical science has advanced enough to defrost your noggin, it’ll be just as able to replace the body that was once attached to it. And as long as your brain is intact, you’re still ‘you’, right?
But freezing and restarting the brain is likely the biggest challenge of all. Because neurons – the brain cells that form the biological basis of everything that you are – are significantly more intricate and vulnerable than any other type of cell.
For one thing, neurons and brain cells are the most metabolically demanding; they consume about a quarter of the body’s available energy just to stay alive. A frozen body has zero available energy. Consider that a stroke is what happens when the blood supply to just one part of the brain is disrupted, even briefly.
The internal structure of a neuron is also very intricate and far more vulnerable to chemical and physical damage. Also, while other tissues may be able to regenerate or repair damage caused by a less-than-perfect cryogenic process, neurons struggle to do this. So, the brain is both more vulnerable to harm from the cryogenic process and less able to recover from it.
And this is key. It’s not just the presence and number of neurons that support our minds and consciousness, but the exquisitely precise and sophisticated way in which they’re arranged and linked. The typical brain contains trillions of spindly microscopic neuronal connections, which are how our memories and identities are stored. Such fundamental connections would be very easily wrecked by the freezing process.
Even if future medicine could rebuild and restore these connections, how would a future neurologist know what connections go where? Unless you have a full molecular-level brain scan before you’re frozen, and that scan is stored with your head or body, trying to rebuild neuronal memories would be like trying to rewrite a burned book by studying the ashes.
Basically, however it’s set up or applied, every modern manifestation of cryonics relies on one vital resource: optimism. And while there’s nothing wrong with that per se, you’d hope people would think twice before gambling their lives on what is currently a very unlikely outcome.
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