Lemurs are nocturnal mammals native to the island of Madagascar. Feasting largely on fruits and flowers, these animals have a bushy tail that serves as an area for fat storage. In winters, when the weather gets rough, lemurs reduce their activity and sleep in curled positions for months together. While this is popularly known as hibernation, scientists call this torpor – where an animal reduces its metabolic rate and temperature to survive harsh weather conditions. Lemurs kept in captivity lose their ability to torpor. But recently published study shows that it is possible to reinduce torpor in captive lemurs.
We have long known about hibernation. We tend to associate bears, snakes and tortoises with the act of hibernation. But it is only recently that science is helping us realise that hibernation consists of multiple-day torpor. These animals engage only in the most important tasks, needed for survival at a slowed-down pace. When the environmental conditions become severe, these animals switch off non-essential tasks in their body. Many question if this would be possible for humans too.
Can humans go through torpor?
To answer the question, we need to look at which animals use torpor. Bears and lemurs are mammals like us. If they can hibernate, it is likely we can as well. A study showed that ancient humans in Spain were able to tolerate hibernation during the extreme Ice Age. But modern-day humans seem to lack this ability. Our bodies do not metabolically slow down during winters to conserve energy.
When did we lose this ability to stop hibernating?
It happened around the same time we gained the ability to control our environment. Our inability to hibernate could be the after-effect of our ability to build structures and devices that keep us safe from freezing temperatures. In modern day, we no longer live in caves, exposed to the elements. We can transport food and fuel across the world. Conserving energy is not the human strategy to survive harsh conditions.
However at a molecular level, our body seems to use the age-old strategy of conservation. The evidence for this is so convincing that one might even say that the ability to hibernate is ingrained in our DNA. Studies carried out for cancer research show that after a chemotherapy session, cells use a slow cell division process. This is similar to the process used by cells waking up from torpor. This evidence shows that our bodies have always retained the ability to counter harsh environments and then return to normal activity when conditions have improved. This is similar to what our ancestors did after the thaw in the Ice Age.
What benefits are associated with torpor?
The advantages of hibernation are not limited to survival alone. Studies involving smaller animals like bats, squirrels, hamsters and mouse lemurs have shown that engaging in torpor increases longevity too. Scientists have found that given their size and metabolic rates, these animals have longer lifespans compared to other animals with similar side and metabolic rates thanks to torpor. For example, the maximum lifespan of bats has been recorded at 41 years. This is almost ten times the lifespan of an animal that size. Scientists attribute longevity to the cells’ ability to tolerate stress while undergoing torpor.
Reduction in body temperature is a key step in inducing torpor. While humans are not capable of doing this by themselves, doctors have medically been able to induce cooling to prevent damage to the body. For example this could be done while the heart is repaired surgically. This is the very principle on which the field of cryonics is based on. It involves reducing the temperature of the body to extremely low temperatures to preserve tissues, neurons and other body parts so that they can be resurrected at a later point.
Drug-induced cryonics and more
But freezing may not be the only method to induce torpor. Scientists are also experimenting with drugs that could bring about this cooling at a cellular level. Similar to how lemurs and bears direct their bodies to lower their temperatures and metabolic rates to induce torpor for a few days, doctors have tried to use a combination of drugs and cryonic storage to try to induce long term torpor. The usage of drugs to reduce temperature is not only limited to inducing torpor alone but it also opens up opportunities for new research into inflammatory diseases such as diabetes and obesity.
Today we do not completely understand the molecular changes that occur when cells are induced or emerge from torpor. Understanding this will be key if we would like to reap advantages from torpor. Scientists are also working on improving cryonic technology and working ways of storing and resurrecting tissues from the ultra-cold. Put together, these technologies will not only help us live again in the near future but also bring the treatments of the future to our lives today.
