Did Ancient Humans Hibernate? | Unveiled

Did Ancient Humans Hibernate?

We have a reasonably clear understanding of how the last 300,000 years or so of human history unfolded. It’s when what science commonly refers to as the modern human took its place on planet Earth. Organising itself and imposing itself on the environment so that now, in the contemporary world, we’re the top dog. But every so often an alternate theory on the human story comes along… imploring us to rethink everything we thought we knew before.

This is Unveiled, and today we’re answering the extraordinary question; did early humans hibernate?

What is hibernation? And why do some animals go through it? At its simplest, it can be described as a prolonged period of rest. It’s usually taken during the winter months when conditions are harsher and food is scarcer… so, in one sense, it’s all about biological efficiency. It’s a chance for a hibernating creature’s body to recuperate, usually at a time of year when it isn’t so worthwhile for it to move, hunt, eat or… do anything else.

Not every animal hibernates, but a wide variety do. From bears to bats to squirrels… from mammals to marsupials to reptiles. The general reasons and processes for hibernation do differ slightly between species, and especially between warm and cold-blooded creatures, but the general idea is always the same. It’s a vital period of physical preservation and energy conservation. Scientists refer to hibernating animals as being in a state of metabolic depression… but it’s nothing to be concerned about. And, ultimately, it’s crucial to ensuring that animal’s waking months are as productive as possible.

So why, you may ask, don’t humans do this? Why don’t we all just hunker down when the weather gets cold, close the curtains, and not open them again until spring? On the bleakest midwinter days, it might be tempting! But, of course, no human hibernates as a matter of biological necessity. The cold weather isn’t as much of a threat to us, we don’t need to worry any more than usual about foraging for food in the winter months, and we don’t need to steer clear of predators for months on end, either (which is another, occasional reason why some animals hibernate). The modern human moves from season to season with relative ease. But, according to one study, it might not have always been this way.

News broke in December 2020 of a co-authored paper, published in the journal “L’Anthropologie”, and titled, “Hibernation in Hominins from Atapuerca, Spain Half a Million Years Ago”. The study involved bone analysis from hundreds of human bone fragments, discovered deep in a cave in northern Spain. In general, the Atapuerca site is a crucial location for anthropologists as they try to piece together the history of us. It was first unearthed in the 1960s and has been providing a basis for eye-opening study ever since - and today has UNESCO World Heritage status. But this could be one of the most unusual theories it has inspired so far.

Conducted by leading researchers Antonis Bartsiokas and Juan-Luis Arsuaga, the hibernation study in particular brought attention to how the Atapuerca bones showed signs of seasonal change. There was evidence of annual bouts of disease, and there were seemingly patterns in bone growth to indicate prolonged periods of inactivity. These human bones shared some resemblance to some animal bones… including to the bones of bears, also found in the same cave system. The suggestion is, then, that early humans, like those from around 500,000 years ago in Spain, may have hibernated. Or, at least, that they may have done something very similar to hibernation, as we understand it today.

But, if that were true, the next question is… why? In this case, Bartsiokas and Arsuaga suggest that the motivation might’ve been much the same as it is for any other animal. For early humans on the Iberian Peninsula, the winter was an extremely difficult time. Food sources dried up, temperatures fell, and daylight hours shortened. The risks of being caught out in the cold were potentially life threatening. And so, they slept. Perhaps not in full hibernation mode, but in something close to it… preparing their bodies for the more promising, more prosperous summer months.

At present, it’s important to note that this is still just one study, and one set of conclusions to draw from it. We can’t definitively say that early humans did hibernate. But we can, with some confidence, predict that they might’ve done in some regions of the world. So, why’s this of relevance today? Well, it actually addresses a major problem that future humans could find themselves facing. A problem not even of this planet, that we’ve all grown to call home.

In space and science circles, crewed space travel is back on the agenda in a big way. And nowadays the moon just doesn’t cut it anymore. Yes, there are initiatives like the Artemis Program aiming to get us back on the lunar surface, but really the world’s eyes are set on Mars. And on even further afield than that. And even allowing for the most optimistic predictions on how future spaceships might look and fly… we’re anticipating months, years, maybe even generations to make just one trip from Earth to somewhere else. One way around this is for our intrepid astronauts to live every minute of their time as they usually would, waking and sleeping all their hours, days and weeks away inside their vessel. But, for most, that’s not exactly an enticing prospect. Another solution, then, is human stasis.

Placing humans into stasis has long been a major plotline in science fiction. For writers and filmmakers, it solves a tricky issue we have with space - that it’s just too big. The distances we’re dealing with when hopping from planet to planet range from thousands of miles to billions of lightyears, and no one wants to sit through the transit. So, could cryosleep be the way to go?

Since 2014, NASA has been working with the private aerospace firm SpaceWorks Enterprises on a “Torpor Inducing Transfer Habitat for Human Stasis to Mars”. With torpor relating to the general metabolic slowdown that happens when a creature hibernates, the plan is to put astronauts to sleep… and then wake them up when we get there. The SpaceWorks proposal is still very much in development, but it would require “medical advances in therapeutic hypothermia” to control an in-stasis astronaut’s low body temperature, as well as total parenteral nutrition to ensure that a long-distance crew is kept well nourished (without the need for them to physically eat and drink). Among the benefits that such a technology could bring, NASA lists a reduction in on-board consumables (meaning a smaller payload, and simpler logistics) plus the potential to lessen the psychological challenges that long distance space travel could bring.

Meanwhile, a 2019 study by the European Space Agency arrived at a similar conclusion. ESA considers human hibernation to be an important “enabling technology” if humanity ever hopes to get off Earth and explore the stars in the future. With this in mind, it painted a picture of what a mission to Mars with human hibernation pods could look like… determining that by travelling in this way “spacecraft mass could be reduced by a third” and that this could result in “several tons of saved mass”. The ESA predictions also included that any proposed hibernation mission would need to rely on hugely advanced AI, as well… but that, thankfully, a trip to Mars shouldn’t result in any long-term health problems for hibernated travellers.

Again, then, we can see that even in the far-off depths of interstellar space, hibernation is arguably the most efficient solution to our problems. Just as animals hibernate to bypass the winter and all the perils that cold weather brings, astronauts could one day hibernate to avoid the obvious (and many) pitfalls of long-distance space voyages. But what’s perhaps most incredible is that if this version of the future does transpire, it could ultimately represent a return to the time of our most ancient ancestors.

Today, human hibernation is a fantastic possibility, a far-off fantasy, and a sci-fi dream, but 500,000 years ago it may have been the norm for early humans, once a year every year. According to the Atapuerca study, our ancient ancestors might’ve developed a most unusual means to get themselves through the winter. They may have done as some other animals do today, and fallen into a deep, unbroken sleep. And that’s big news for everyone… from anthropologists to rocket scientists!