Humans
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Life in the Ice Age was no walk in the park, yet Neanderthals managed to endure hundreds of thousands of years of repeated glaciations, only to perish just a few dozen millennia before the start of the Holocene. To last that long, our extinct cousins must have had a few heat-conserving tricks up their sleeve, and researchers are now beginning to understand just how Neanderthals managed to survive the bitter cold.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Snuggling up with a woolly mammoth may have been the cosiest way to make it through a glacial period, but given the unlikeliness of this scenario, researchers suspect that fire could have been the greatest ally of the Neanderthals during the Ice Age. Despite this, there remains some debate over whether or not these archaic humans actually knew how to make fire from scratch, with some experts suspecting that embers from wildfires may have provided the only source of ignition for Neanderthal hearths.
Whether they could conjure fire or not, though, there’s ample evidence that Neanderthals made use of this life-saving element. At one site in Catalonia, for instance, researchers found the remains of channels dug beneath a fireplace in order to deliver oxygen to the flames, suggesting that Neanderthals may have understood the basics of pyrodynamics.
Clothing, meanwhile, would have prevented our ancient relatives from freezing their bits off, and while the animal hides they wore have all long-since decomposed, archaeologists have found indirect evidence for Neanderthal tailoring. Eyed sewing needles made from animal bones, for instance, have been recovered from the famous Denisova cave in Siberia, dated to a period when the site was inhabited by Neanderthals some 50,000 years ago.
Other osseous tools known as lissoirs, meanwhile, are commonly found at Neanderthal sites and are believed to have been used in the production of leather garments. According to the authors of a new study, “these tools may have been invented by Neanderthals… and are directly comparable to tools used by modern leatherworkers to rub hides to make them more waterproof and/or polished.”
In addition to these behavioral interventions against the cold, biological adaptations are likely to have aided the Neanderthals during glacial periods. For instance, the study authors point out that the high body mass, broad trunk, and short limbs of this ancient species would have reduced their relative surface area, thus restricting heat loss.
They also point to indirect evidence that suggests that Neanderthals may have had a higher basal metabolic rate (BMR) than we do, meaning they generated more heat. This may have been partially mediated by elevated levels of thyroid hormone, as has been observed in some indigenous Siberian reindeer herding communities and has been associated with increased BMR.
At the same time, Neanderthals may have possessed more brown fat than we do. Previously thought to be present only in babies, this type of fat has recently been identified in adults, and is known to produce heat when under acute cold stress.
Typically found in the tissues surrounding the carotid arteries and jugular veins, brown adipose tissue (BAT) could conceivably have formed part of the Neanderthals’ arsenal of cold adaptations, argue the study authors. “Given its thermogenic properties, BAT could have been critical to Neandertal survival in glacial regions, helping to maintain core body temperature by insulating the life-sustaining major blood vessels,” they write.
Finally, there’s the long-standing controversy surrounding Neanderthals’ noses. Until recently, it was thought that these wide nasal openings were unsuitable for cold weather and that Neanderthals must have possessed some sort of internal structure that helped them warm up the air they inhaled. However, this theory was recently disproven when researchers gained the first-ever look at the internal morphology of the Neanderthal nasal passages, revealing that these proposed features did not actually exist.
According to the study authors, though, Neanderthals possess “strikingly large” bony structures called turbinates in their noses, which helped to filter, warm, and humidify inhaled air.
Taking all this evidence together, the researchers write that Neanderthals “were cold adapted not through a single hallmark, but through an integrated suite of traits,” including the use of fire and clothing as well as a range of biological and physiological mechanisms.
“This integrated perspective helps explain Neandertals' ecological breadth and their persistence across varied climates for over one hundred thousand years,” they conclude.
The study has been published in The American Journal of Human Biology.
