Will Human Hibernation Ever Be Possible? 

Health and medicine explained.
Sept. 5 2014 8:02 AM

Do Lemurs Hold the Secret to Suspended Animation?

What we might be able to learn from our closest hibernating cousins. 

140904_MEDEX_Hibernation
A fat-tailed dwarf lemur in an artist’s rendering of a suspended animation chamber.

Photo illustration by Slate. Photos by Shutterstock.

Excerpted from Shocked: Adventures in Bringing Back the Recently Dead by David Casarett. Out now from Current.

You know all about suspended animation because it makes an appearance in virtually every science-fiction movie that’s ever been made. Usually it’s portrayed as a handy device for space travel. But what you probably don’t know is that suspended animation isn’t just science fiction. It’s real. And it could save lives.

Suspended animation is really just slowed metabolism, like hibernation. Think of it as artificial hibernation. When animals hibernate (and when science-fiction characters venture off-world), they’re in a state in which their cells have downshifted to low gear and they need very little oxygen.

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That’s handy for intergalactic travel, of course. But what if we could use that trick in situations in which our cells—and particularly our brain cells—don’t have access to much oxygen? That might be the case for a patient who has suffered a cardiac arrest and who isn’t breathing. Or someone injured in a car accident, or someone with a serious gunshot wound. Or a soldier injured on the battlefield.

These people all have one thing in common: Their brains and other vital organs aren’t getting enough oxygen. And their cells are dying. Biologists call that process of cell death “apoptosis.” Soon, those people’s bodies will be dying. Biologists just call that “death.”

But suspended animation could prevent those deaths simply by decreasing the amount of oxygen that those people need to survive. Decrease their metabolism by 50 percent and we double the time that they can survive without oxygen (more or less). Decrease it by 90 percent and we increase it tenfold. Normally, even 15-20 minutes without oxygen will typically cause serious brain damage, but in theory, suspended animation could open that window to an hour, or even a day.

That’s why lots of researchers are very interested in understanding how hibernation works in animals, and that’s why I’m standing in a small, cool room that’s lit only by a weak red light. I’m here because this room holds the secret—maybe—to new treatments that will save lives and help us cheat death by putting people into suspended animation.

Specifically, I’m here to meet lemurs. They’re the only primates that hibernate. So lemurs might be able to teach us humans how to do the same thing. Peter Klopfer, one of the founders of the Duke Lemur Center, is a fervent believer that lemurs are the best way to learn hibernation lessons that could help people.

Soon my eyes adjust enough to see three little lemurs hopping around their cage. I’m surprised by how small they are. They have big eyes and fat tails. And they’re maybe 12 inches long.

As we watch the lemurs frolic, Klopfer gives me a whispered summary of lemur hibernation research. He tells me that until very recently no one thought that any primate could hibernate. Bears, yes. Rodents, certainly. But everyone thought that when primates face a tough winter, we just bundle up and tough it out.

In 2005, though, a German team of researchers collected the first evidence of prolonged hibernation in fat-tailed dwarf lemurs (Cheirogaleus medius). That discovery raised the very intriguing possibility that other primates—like humans—that don’t normally hibernate might be able to pull off the same trick. Lemurs are much closer to us, genetically, than other hibernating animals are. And that’s important, because if we want to understand how hibernation works in a way that might someday help people, it pays to study hibernation in an animal that’s as close to us as possible.

This is the challenge of interspecies research. If we find the secret ingredient of hibernation in another species that happens to fit our physiology, then there may be enormous opportunities for saving lives. But if whatever provokes hibernation in another species isn’t in our physiologic repertoire, then we’re back where we started. So Klopfer and his colleagues are looking for something in the lemur’s repertoire that we also have in ours.

So what’s the secret to lemur hibernation? Now we’ve left the lemurs to themselves, and Klopfer is taking me on a tour to see some of the obviously nonhibernating lemurs that are swinging merrily through the trees on the grounds of the sprawling sanctuary.

“Hibernation,” Klopfer tells me as we walk, “isn’t a conserved trait.” He pauses. “It’s convergent.” Klopfer adds this last little clarification with a clipped precision that seems like it should make things crystal clear.

Alas, it doesn’t. I suspect that my blank look reveals my ignorance. Conserved? Convergent?

What he means, he explains, is that hibernation is something that species have evolved to do in very different ways. Hibernation in a squirrel might look like hibernation in a lemur or a groundhog, or a bear. In fact, the physiology—low temperature, slow metabolism, low blood pressure—look exactly the same. And indeed, there are plenty of researchers studying hibernation in all of those animals.

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