Dec 29, 2020

Early Humans May Have Hibernated Through Long Winters, Study Hints

While many folks might long to merely sleep through this complete winter, humans - unlike plenty of other mammals - haven't got the capacity to hibernate.

But a newly published study has investigated if early humans had this ability at some point. The results – although preliminary – surprisingly suggest that they did, whether or not they weren't great at it.

When a bear wakes up from its extended torpor (a style of energy-conserving sleep state often used synonymously with hibernation), sleepy and prepared for a feed, their bones and muscles are relatively identical as they were before, spared from the body's self-feeding frenzy over the winter.

Bears have specialized metabolic processes to safeguard them from this extended slumber, but sometimes this process doesn't quite head to plan. as an example, animals can find themselves with a bunch of diseases post-hibernation if they do not get enough food reserves before they're going down for the winter.

"We need to emphasize that hibernations aren't always healthy," paleoanthropologists Antonis Bartsiokas and Juan-Luis Arsuaga write in their new paper.  

"Hibernators may suffer from rickets, hyperparathyroidism, and osteitis fibrosa if they are doing not possess sufficient fat reserves. These diseases are all expressions of renal osteodystrophy in step with chronic renal disorder."

The researchers believe this might are the fate of some human ancestors whose remains were discovered in an exceedingly Spanish cave called Sima de Los Huesos – the chasm of bones. This deep shaft within the Cave Mayor of Sierra de Atapuerca is home to an implausible number of fossils, with archaeologists having discovered thousands of hominin skeletal remains that are around 430,000 years old.

This is long before Homo sapiens walked the world, and although there's some debate about which human ancestor the fossils are from, a minimum of some are H. heidelbergensis.

Working out if human ancestors once possessed a type of hibernation-like state thousands of years after the actual fact seems like an impossible task, but the team thinks they need found some tell-tale marks on the fossils.

"The evidence of annual healing caused by non-tolerated hibernation in adolescent individuals [points] to the presence of annually intermittent puberty during this population," the researchers write, explaining that other signs of ergocalciferol deficiency from lack of exposure to sunlight are evident in bone defects just like the 'rotten fence post sign'.

"The hypothesis of hibernation is in keeping with the genetic evidence and therefore the proven fact that the Sima de Los Huesos hominins lived during an ice age."

The idea is that these ancient hominins may need been trying to sleep through the colder months, so their bones show the scars of months of sleeping without enough fat stores, an absence of fat-soluble vitamin, and - in teenagers - weird seasonal growth spurts.

Before we are able to claim that human ancestors once did indeed hibernate, we've got to recollect that this research is incredibly preliminary. Even the researchers themselves admit that this sounds a small amount like "science fiction".

"While many questions about their life histories and metabolism are still open, there's little question on the immense consequences that hibernation has for hominin/human physiology and life history," they write. 

"The notion that humans can undergo a hypometabolic state analogous to hibernation may sound like a fantasy but the very fact that hibernation is employed by very primitive mammals  and primates, suggests that the genetic basis and physiology for such a hypometabolism can be preserved in many mammalian species including humans."

We will need lots more info before we will confirm if these ancient human ancestors were indeed hibernating and if it absolutely was the case, how the human species ended up losing the flexibility entirely.

"It may be a very interesting argument and it'll certainly stimulate debate," forensic anthropologist Patrick Randolph-Quinney of North Umbria University told Robin McKie at The Guardian.

"However, there are other explanations for the variations seen within the bones found in Sima and these should be addressed fully before we will come to any real conclusions."

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