eli5 Why can human embryo’s be frozen but not human adult?
In: Biology
Isn’t there a company that freezes whole people?
Size. The freezing and defrosting process of something small like an embryo is vastly quicker and easier than an adult.
The biggest thing they have managed to freeze and defreeze is a hamster.
There’s just noway to get the defreezing agent into the tissue cells quick enough. It would invariably lead to cell death and probably death death.
Either by not entirely defreezing the person or by defreezing them and cooking them in the process.
There’s a relevant Tom Scott about this, which actually relates to the invention of the microwave. Basically, anything bigger than a small rodent cannot reheat quickly and evenly enough to be able to reanimate.
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I read that they were once successfully able to freeze and unfreeze dogs, half the dogs had brain damage but still.
The larger the organism they harder it is to avoid complications.
Anything can be frozen, it’s the unfreezing that becomes the problem. In my lab, I would freeze cells all the time as a kind of record of progress. You add special buffers to prevent ice crystals from tearing the cells apart and then cool them down to eventually -80 C, and then you can cryogenic freeze them in liquid nitrogen. You slowly “unfreeze” them in crushed ice / water slurry which is just at about 0.2 C. You can’t do that with organs or I should say we haven’t figured out how just yet. We do transport chilled organs, but they aren’t frozen. If we could do that organ donations would much, much less of a logistics and timing issue.
I have seen goldfish that where left outside for some reason and freeze solid in the ice. The next day was very warm and the ice melted and the fish started swimming again for a while… yet eventually died, so it is possible. No clue how it happened at the cellular level.
edit: words
My actual eli5:
Embryos are super tiny with a few simple parts. You can freeze/defrost it fast enough that nothing breaks.
Adults have tons of complex parts that would break if you froze them, and unfreezing them would break more since it takes so long, and they all have to be working at once or it doesn’t work.
I would then take a bit of an ice cube out of a freezer, and sit it on the counter next to some frozen piece of meat. In ten minutes I’d show them the water from the sliver of ice cube that already melted, and then knock the frozen meat off of the counter to get a good thud. Maybe even show them in an hour how only a small part of the outside is even remotely defrosted. No good, you see, because everything in an adult has to be working at once. We can’t magically make it unfreeze all at once. That is one dead adult we’re eating for dinner. (Bonus points if you’re a cannibal and you actually used a frozen adult for this).
Simple small thing, ok. Big complex thing, not ok.
It skips some details, but, it gets the job done.
it’s a function of limiting current technology. the concept is more or less simple, and we’ll get there. there was an ELI5 question the other day asking why freezer burn exists. similar reasoning, and avoiding that is key.
I’m assuming you’re talking about reanimation.
Tom Scott recently published a very interesting video, where he interviewed a scientist tangentially involved in the invention of the microwave, he was using it to experiment on reanimating mice. The short answer to your question, is that they were only able to get it to work for small things – it worked for some of the mice, but for larger creatures it doesn’t work well, and that goes for both the reanimation process and also for the freezing process.
The bigger a living organism is, the harder it is to freeze it quickly enough to not permanently damage it.
This is because, generally speaking, you can only cool the surface of something, but you have to cool its whole volume.
If you have something that you can freeze and you make it twice as big, the new, bigger thing has ~8x the amount of material to cool, but only ~4x the surface area to cool it with. So it’s effectively twice as hard to cool down.
This just gets worse and worse as you get bigger and bigger. Freezing an embryo is thousands of times easier than freezing a grown adult. There were experiments decades ago where hamsters were frozen and revived, but that’s about as large as can be done with living things on Earth.
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