I mean, sure, there is mummification and and some bodies being naturally preserved due to coldness or dryness, but I’m talking more about the idea of cryonics- the idea that you could stop a biological organism’s entire metabolism in some kind of suspended animation and then later thaw them out and be able to continue living. Most of this is just science fiction though and greatly exaggerated. All of the people who have gotten their bodies cryopreserved as adults are people who have died and it’s essentially just mummification instead of suspended animation.
In: Biology
It’s incredibly difficult to get everything back up and running at the same time. If it’s sperm or embryos that are very small, it’s not that difficult to warm everything up at once.
For an adult human body, that’s much harder; by design, the body insulates its organs, making it hard to warm them up before other things are already warm and need the organs to live. For example, if you were thawing someone out and thawed their skin first before the heart, the skin would start dying because there’s no blood or oxygen being provided by the heart and lungs.
The water in mature cells will crystallize while freezing, causing damage to the cell walls and internal bits. The other stuff is just genetic information, and while some tiny amount may be destroyed or corrupted during the freezing process, there is enough that survives to be used as a blueprint to make the bigger stuff.
*embryos get the water swapped out for a fancy antifreeze.
In addition to what these others answers say I work in cell biology and can speak more of how we freeze the cells. But to freeze the cells we use a liquid called DMSO (dimethyl sulfoxide) which is a substance with a similar freezing temperature and osmotic pressure as water, but it doesn’t expand when freezing so that cells submerged in it won’t die. The trick is that DMSO is actually poisonous to cells so you have to quickly do the media transfer then immediately freeze the cells (but not too quickly) or they start to try to use the DMSO and get poisoned. So this presents a logistical challenge for freezing whole people because with cell suspensions you can just change out what all the cells are using at once. But with people you have lots of cells supplied by a circulatory systems which takes varying times to reach various regions of the body and it would take very long to replace the water in your body with DMSO
Because we are too thicc…
Seriously tho, think of trying to heat up a big chunk of frozen food. If you heat it up too fast, the middle will be cold. If you heat it at a lower temperature, but for too long it will dry out. It’s like that for cryo, but in reverse.
We just haven’t found the sweet spot to freezing larger tissues at an even rate.
The big reason most living things can’t survive freezing is because large, sharp ice crystals form in their cells and pop them like balloons from the inside – that’s basically what frostbite is. When something freezes really quickly all at once, the resulting ice crystals are a lot smaller than if that thing is frozen slowly. For a more accessible example, that’s part of the reason why ice cream is smooth but if you put cream in your freezer it’ll turn out slushy – commercial ice cream is frozen extremely quickly so the ice crystals are small enough that you can’t detect them.
So the reason we’re not currently able to cryopreserve, say, a whole human, is because it would take a lot of time for the parts in the middle of the body to actually freeze and you’d get large ice crystals which damage the cells beyond repair. You’d really effectively preserve the skin while causing massive internal frostbite. Small things like sperm or embryos (or lots of other cells that we freeze to preserve) are small enough to survive that process because they freeze all the way through so quickly. Additionally we tend to use compounds called cryoprotectants in that process which also reduce the size of ice crystals.
The top comment has some misconceptions. Cryonics companies do exist and they now use vitrification, rather than freezing, which avoids ice formation.
The reasons animals or humans can’t currently be revived from _that_ are that the vitrification mixtures that are used are themselves toxic, and there is of course damage that occurs. The hope is to preserve the structure (esp. of the brain) for future technology to potentially reconstruct – not to keep tissues or organs in a near-functional state.
The core idea is preventing “info-death” – there should be enough information that can be used to restore the brain in theory. Whether that is accomplished is debatable. Some people clearly think the cost/benefit analysis is favourable, and I am inclined to think that viewpoint makes sense.
Small bits of tissue like blood vessels have been successfully vitrified and revived, but nothing very large. If it’s at all possible to revive current cryonically preserved people and animals, it will probably require far more advanced technology.
Latest Answers