Archaeologists have put forward a remarkable idea neanderthals may have once followed the example of other mammals by hibernating. The intriguing idea originated from evidence unearthed from bones discovered at one of the world’s most important fossil sites.
This suggests our hominid ancestors may have dealt with extreme cold 400,000 years ago by sleeping for remarkably-long periods throughout the winter.
Apparent proof arrives in the form of signs of damage, such as lesions in early humans’ fossilised bones.
There is an uncanny resemblance to bones belonging to other animals that hibernate.
This is controversially used to argue our neanderthal predecessors coped with prolonged extreme temperatures by significantly slowing their metabolisms and sleeping uninterruptedly for months at time.
Their highly-contentious conclusions are based on excavations at the pit of bones cave, known locally as Sima de los Huesos, in Atapuerca, northern Spain.
Juan-Luis Arsuaga, who led the site’s first excavation, and Democritus University’s Dr Antonis Bartsiokas think the fossils could indicate seasonal variations, suggesting that bone growth was disrupted for months of the year.
The pair write these early humans found themselves “in metabolic states that helped them to survive for long periods of time in frigid conditions with limited supplies of food and enough stores of body fat”.
They write: “They hibernated and this is recorded as disruptions in bone development.”
And although they admit their proposal “may sound like science fiction” they do draw attention to the fact other mammals including primates such as bushbabies and lemurs also hibernate.
They researchers wrote: “This suggests the genetic basis and physiology for such a hypo-metabolism could be preserved in many mammalian species including humans.
“The pattern of lesions found in the human bones at the Sima cave are consistent with lesions found in bones of hibernating mammals, including cave bears.
“A strategy of hibernation would have been the only solution for them to survive having to spend months in a cave due to the frigid conditions.”
Additionally, the hypothesis is given added weight with the discovery of a hibernating cave bear’s (Ursus deningeri) remains discovered in the Sima pit.
They interpret this as making it increasingly believable to suggest neanderthals were also hibernating “to survive the frigid conditions and food scarcity as did the cave bears”.
Counter-arguments are also pre-emptively assessed by the archaeology experts in their paper.
For example, modern-day Inuit and Sámi people live in equally inhospitably cold conditions and do not hibernate.
However, Mr Arsuaga and Dr Bartsiokas suggest an answer could lie in the fact fatty fish and reindeer fat provide these indigenous people with food during winter, precluding the need for them to hibernate.
The environment around Sima site half a million years ago would, in contrast, not have provided anything like sufficient food.
The pair write: “The aridification of Iberia then could not have provided enough fat-rich food for the people of Sima during the harsh winter – making them resort to cave hibernation.”
Dr Patrick Randolph-Quinney, a Northumbria University forensic anthropologist, believes they have put forward an interesting argument.
He said in a statement: “There are other explanations for the variations seen in the bones found in Sima and these have to be addressed fully before we can come to any realistic conclusions. That has not been done yet, I believe.”
Dr Chris Stringer of the Natural History Museum also believes their theory offers an interesting additional to the arena of scientific debate.
He said: “The idea is a fascinating one that could be tested by examining the genomes of the Sima people, Neanderthals and Denisovans for signs of genetic changes linked with the physiology of torpor.”