All over the northern hemisphere, millions of animals are tucked up somewhere safe, hibernating through the cold, ready to come up smiling in spring. Bats, marmots, hedgehogs, bears. And not just in the wintry north: animals in the tropics do it too, such as some fruit bats and one primate, the dwarf lemur. It had long been a dream to copy the process in people 鈥� and by the 2050s, it had become a reality.
Animals hibernate at different 鈥渄epths鈥�, with varied reductions in metabolism and body temperature. Arctic squirrels are the champions, dropping their metabolic rate by 98 per cent and their body temperature to a freezing -3掳C (27掳F). It wasn鈥檛 possible to replicate such extremes in humans without risking cardiac damage, but people could tolerate a gentler, bear-like hibernation. Bears, and humans entering the physiological state of reduced activity known as torpor, enjoy fairly shallow hibernations, cutting their metabolic rate by 80 per cent and decreasing body temperature to 31掳C (89掳F).
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Earlier in the 21st century, cryopreservation 鈥� infusing people with ice-cold saline to reduce body temperature 鈥� began to be used on those with life-threatening wounds or diseases. But it was a gruelling process if you just wanted to skip winter, and it wasn鈥檛 great for the skin either. When the genetics of hibernation were uncovered in a range of mammals, then activated in humans, this allowed less-intrusive, 鈥渘atural鈥� hibernation.
The trick is to first activate genes that reduce metabolism, then get the body temperature down. If you do it the other way round, you have a fight on your hands, as the metabolism tends to try to accelerate in order to combat the temperature loss. Scientists had found ways back in 2019 to trick the brains of pigs and rats into , and the method was modified to work in humans.
Deep hibernators such as Arctic squirrels live off their fat for long periods, without drinking or passing waste during their hibernation. Shallow hibernators such as bears bring food with them and wake up from time to time to snack. Since humans undergo bear-like hibernation, this was the protocol used, but with small amounts of food inserted directly into the stomach by a tube. The method meant that people didn鈥檛 need to gain a lot of weight before hibernation, and it stopped deterioration of essential gut symbionts 鈥� that is normally lost as waste, for use as a nutrient.
Many people used hibernation as animals do 鈥� to skip the winter. It was done not so much to avoid the gloomy symptoms of seasonal affective disorder as to enjoy a boost in lifespan. Biologists knew hibernating animals live longer than non-hibernators of the same size, because their bodies age more slowly during hibernation. In a state of deep torpor, recycle and repair pathways in the body are switched on and cells undergo what is effectively a deep clean. All the bits of damage that contribute to ageing are mopped up or fixed. Human life expectancy, boosted by cycles of hibernation, reached 130 to 150 years.
This breakthrough initially caused great upheaval, worsening inequalities in society as rich people paid to extend their lifespans. Human hibernation centres had to be guarded and sited in secret locations, to prevent attacks by the non-hibernating masses. Eventually, governments intervened to regulate access to the technology. Most countries offered hibernation as a state-provided health resource, giving everyone access to the benefits.
Society became highly intergenerational, something that previously was only pronounced at Christmas and other times when extended families got together.
Future Chronicles explores聽an聽imagined history聽of聽inventions and聽developments yet to come.聽Rowan Hooper is the聽podcast editor at New Scientist and author of How to Spend a Trillion Dollars: The 10 global problems we聽can actually fix. You can follow him on X @rowhoop
