Why Don’t Humans Hibernate?

Over 100 years ago, in 1900, an article was published in the British Medical Journal about a place in Russia called Pskov, where the people would engage in a practice of “winter sleep.”

Families would huddle together and sleep nearly all day and night. They’d take turns keeping the stove fire alive, and they’d all get up once a day to eat a little bread. This “hibernation” would continue all through the harsh winter months until the grass was green again.

Similar stories are told about peasants in 18th-century France.

There isn’t any strong evidence that these narratives are true. It’s likely that these accounts of apparent “human hibernation” have been exaggerated or misunderstood.

What is Hibernation?

Hibernation is a state of reduced metabolic activity that animals enter to conserve energy.

During hibernation, animals enter a state known as torpor—a deep sleep-like state in which their body temperature, heart rate, and breathing rate are all significantly reduced. 

Hibernation allows animals to survive long periods with minimal (or completely without) food. Some animals, such as bears, will eat large amounts of food before hibernating to build up fat stores that they can use for energy during the hibernation period.

Hibernation is a common adaptation among many animals, including bears, squirrels, bats, frogs, bees, snails, and hummingbirds.

Hibernation is most common in animals that live in cold climates, where it allows them to conserve energy during the winter months when temperatures are too low for them to be active hunting and foraging. However, some animals that live in warm climates, such as some species of bats and bees, also enter a state of torpor during periods of food scarcity or extreme temperatures.

Why Don’t We Hibernate?

Humans do not hibernate because, unlike many other animals, we do not appear to have the biological adaptations that are necessary for hibernation. 

Hibernation is a complex process that involves significant changes to an animal’s body to an animal’s physiology, including a dramatic reduction in heart rate, breathing rate, and body temperature. These changes would potentially be dangerous for humans, as our bodies are not adapted to withstand such extreme changes in temperature and heart rate.

Recent research indicates that human ancestors from half a million years ago may have had the ability to hibernate. If it is true, it is likely that modern humans lost this trait over time as we evolved and adapted to different environments. 

Hibernation may have become less advantageous, or it became more advantageous to not hibernate. The humans that reproduced, hunted, and defended from predators all year round were more likely to survive and pass on their genes than the ones who were inactive for several months each year.

Innovations such as fire, clothing, and better food gathering and storing practices may also have helped make hibernation unnecessary for our species.

Applications of Human Hibernation

If our evolutionary ancestors had the ability to hibernate, some researchers believe this ability may still lie dormant in our genetic code.

Through advancements in medical technology, human hibernation may be possible in the future. Already, healthcare teams will occasionally induce therapeutic hypothermia in high-risk situations, such as traumatic injuries, transplants, and difficult surgeries.

Although this isn’t exactly hibernation, therapeutic hypothermia reduces body temperature and breathing rate to a point where the risks of life-threatening emergencies may be reduced.

Further advancements in this domain may unlock more possibilities in medicine and in space travel. For example, long space flights may become more achievable if there is a way to keep inactive people safe and healthy with significantly fewer resources.

But for now, there aren’t any known ways to safely put a human into a prolonged state of torpor. Reducing the body temperature and metabolic functions in this way carries a great risk of organ failure, nutritional deficiencies, immune system malfunctions, and other life-threatening conditions.