The wood frog hibernates at temperatures of around 26 degrees Fahrenheit (-3.3 degrees Celsius). Their bodies are cold and stiff, seemingly frozen solid, but in the spring, they thaw and come back to life with no harm done. Other animals can perform similar feats, but how is it done, and could it hold the key to making cryogenics viable?
The wood frog's hibernation ability is so impressive because in most organisms, when exposed to freezing temperatures for a prolonged period, the water in cells freezes, and cells are ravaged by the resultant ice crystals. But in wood frogs, the animal's metabolism plummets and cells empty of some of their water as glucose floods in. The high levels of glucose act as an antifreeze, preventing the water in cells from freezing.
The process could show the way for cryonics, where people commit their bodies to being frozen in the hopes of one day being brought back to life. (Cryogenics refers to the study of very low temperatures; cryonics is the actual process of freezing human bodies for future resuscitation.)
Most mainstream scientists don't see cryonics as very credible -- more scam than science. Numerous impediments stand in the way of making the process feasible. After all, since people are only cryonically frozen after they die, techniques must be devised to not only revive them but to repair whatever damage exists in the body, all the way down to the cellular level. Similarly, current cryonic technology appears to damage the brain, though some studies show that loading the brain with cryoprotectants can minimize damage. Cryoprotectants are essentially antifreezes, mimicking the role of glucose in wood frogs, but while these liquids may prevent freezing-induced tissue damage, they may still be toxic or otherwise harmful.
Cryonics facilities use temperatures colder than -300 degrees Fahrenheit (-184.4 degrees Celsius) -- far lower than those that wood frogs face in nature, so adapting the ability to humans may require reconsidering how to freeze human remains. At the moment, these extremely low temperatures dry out cells, harming the body.
For now, in the minds of some researchers, wood frogs provide a conceptual framework for how to proceed. Eventually, advances in freezing processes, nanotechnology, and learning from examples in nature could move cryonics from the realm of the fanciful to the plausible.
Still, while the wood frogs example is alluring, it's not cryonic preservation in the true sense. These frogs don't actually die. And in replicating this process, scientists have only been able to freeze and revive individual animal organs for a short period of time -- a far cry from reviving an entire organism.