Humans Used to Be Able to Hibernate, Evidence Suggests
It will be the ultimate alien megastructure, one that will signal the passage of our species from a planetary species to an interstellar one.
While it’s difficult to make a conclusive case after thousands of years, researchers have combined observations from the fossil record and believe humans had a form of hibernating ability in the long-ago past.
The results show through evidence like bone structure and growth over time, which scientists can use to backform what people were eating and doing during the seasonal cycle.
Would you hibernate through the winter of 2021 if you had the ability?
Homo sapiens—that’s us!—evolved somewhere around 300,000 years ago. In this research, paleoanthropologists from Greece and Spain studied fossil evidence from about 500,000 years ago, making those the remains of an extinct humanlike ancestor. “[W]e examined the hominin skeletal collection from Sima de los Huesos, Cave Mayor, Atapuerca, Spain, for evidence of hyperparathyroidism after a thorough review of the literature,” the researchers explain in their paper.
The location in the caves of Atapuerca, a precious archaeological site where scientists have found over 1,600 human fossils from a key period in the evolutionary timeline of Homo sapiens, is important for the specific scope of this research. Caves are a natural shelter, and researchers study them as an example of an early type of settlement as humans developed technologies, like agriculture, that enabled them to “put down roots.”
In this case, the researchers believe those roots included staying inside the caves a lot of the time, including through the cold and difficult winter months.
Today, we know that hibernating animals walk a very fine line of preparation and subsistence, building fat stores and activating biological triggers to lower body temperature and metabolism. But while modern humans have technology that staves off nutritional diseases, for example, our prehistoric ancestors had no such luck.
It’s in these absences, which leave physical marks on the human skeleton, that researchers have found their clues. Here’s just part of the laundry list of self evident health conditions:
“We found trabecular tunneling and osteitis fibrosa, subperiosteal resorption, ‘rotten fence post’ signs, brown tumours, subperiosteal new bone, chondrocalcinosis, rachitic osteoplaques and empty gaps between them, craniotabes, and beading of ribs mostly in the adolescent population of these hominins. [T]hese extinct hominins suffered annually from renal rickets, secondary hyperparathyroidism, and renal osteodystrophy associated with Chronic Kidney Disease – Mineral and Bone Disorder (CKD-MBD). We suggest these diseases were caused by poorly tolerated hibernation in dark cavernous hibernacula.”
The scientists found many examples of destruction or weakening of the skeleton based on an existing understanding that these signs are caused by diseases. And because of the periodic nature—happening annually, but not constantly—they believe they can pinpoint these seasonal damages to a survival tradeoff made by our ancestors.
They chose to spend the worst part of the year trying to sleep through it inside of relatively safe caves, and to do that, they sacrificed nutrition and vitamin D from the sun.
What does this all mean? Well, the human metabolism is unusual on its own, but it also fits into the bigger picture of how mammals and then humanoid mammals evolved. To hibernate requires even another step beyond what we have—not only to burn enough food fuel to keep our warm-blooded bodies working, but to store up and safely expel enough to survive.
Understanding which species managed this feat could help archaeologists understand why Homo sapiens emerged as the ones who are still here.