That’s a fair question. I was assuming that creatures which can survive full dehydration are so different at the cellular level that nothing less than genetic redesign would do the job, but I’m guessing.
I think part of the problem, too, is that animals who can survive full dehydration, or being thoroughly frozen within and without, are small. We don’t often realize just how big humans are, even for land-dwelling tetrapods. We’re very large, very active, and very resource-intensive—certainly there are bigger land animals about today and in our recent past, and very much bigger ones in the fossil record (brachiosaurs, anyone?), but even then we still qualify as megafauna.
The consequences of that size, especially in light of our activity level, are significant. Human physiology is very adapted to dissipate heat well (and our water intake is a big part of that), yet we still routinely have trouble doing it fast enough to avoid ill effects, forcing us to adapt culturally and individually to the problem. We have to conserve quantities (of temperature regulation, of water) at fairly specific levels; our physiology is critically dependent on them.
So, yeah—if people can be put in suspended animation of some sort (regardless of mechanism), it’s gonna have to take our particular case into account. You can flash-freeze a mouse, thaw it, and get biological activity after (they don’t exactly go on to live long and prosperous mousey lives, but they do come out the other side for a bit). A mouse is tiny; you can’t extend that to a human without different physics becoming relevant. You can dehydrate a tardigrade quickly (just let it do its thing in a low-moisture environment for long enough until it loses enough water) and then leave it sitting until it gets doused again; you can’t do that to a human, because we have a lot of water to lose, our bodies fight to hang on to it, our health declines rapidly as we lose even modest amounts, and we proceed straight to death once quantities are insufficient.
I think part of the problem, too, is that animals who can survive full dehydration, or being thoroughly frozen within and without, are small. We don’t often realize just how big humans are, even for land-dwelling tetrapods. We’re very large, very active, and very resource-intensive—certainly there are bigger land animals about today and in our recent past, and very much bigger ones in the fossil record (brachiosaurs, anyone?), but even then we still qualify as megafauna.
The consequences of that size, especially in light of our activity level, are significant. Human physiology is very adapted to dissipate heat well (and our water intake is a big part of that), yet we still routinely have trouble doing it fast enough to avoid ill effects, forcing us to adapt culturally and individually to the problem. We have to conserve quantities (of temperature regulation, of water) at fairly specific levels; our physiology is critically dependent on them.
So, yeah—if people can be put in suspended animation of some sort (regardless of mechanism), it’s gonna have to take our particular case into account. You can flash-freeze a mouse, thaw it, and get biological activity after (they don’t exactly go on to live long and prosperous mousey lives, but they do come out the other side for a bit). A mouse is tiny; you can’t extend that to a human without different physics becoming relevant. You can dehydrate a tardigrade quickly (just let it do its thing in a low-moisture environment for long enough until it loses enough water) and then leave it sitting until it gets doused again; you can’t do that to a human, because we have a lot of water to lose, our bodies fight to hang on to it, our health declines rapidly as we lose even modest amounts, and we proceed straight to death once quantities are insufficient.