In a paper published in the journal L’Anthropologie, Juan-Luis Arsuaga –who led the team that first excavated at the site – and Antonis Bartsiokas, of Democritus University of Thrace in Greece, argue that the fossils found there show seasonal variations that suggest that bone growth was disrupted for several months of each year.

They suggest 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 hibernated and this is recorded as disruptions in bone development.

The researchers admit the notion “may sound like science fiction” but point out that many mammals including primates such as bushbabies and lemurs do this. “This suggests that the genetic basis and physiology for such a hypometabolism could be preserved in many mammalian species including humans,” state Arsuaga and Bartsiokas.