Did early humans hibernate? / Could we really sleep in space for years? | Dr Antonis Bartsiokas

The central claim is that some early humans—specifically the Sima de los Huesos population at Atapuerca in Spain—may have entered a hibernation-like state for months, and that their bones preserve medical signatures of that physiology. The argument matters because it challenges the common assumption that humans can’t tolerate prolonged cold, darkness, and metabolic shutdown; it also reframes “hibernation” from a purely animal trait into a potentially latent human capability with implications for medicine and long-duration spaceflight.

Hibernation is defined as a physiological adaptation to anticipated famine that drives down metabolic rate and body temperature under constant darkness. Darkness and food scarcity are treated as key triggers: darkness is linked to cortisol release from the adrenal glands, which contributes to hypothermia and even suppresses growth. Famine is emphasized through comparisons with Arctic peoples—who do not hibernate because they have year-round access to fat-rich foods that supply vitamin D—contrasting with animals that must endure winter scarcity.

Ancient and ethnographic accounts are then used to support the idea that humans can fall into long, low-activity states. Herodotus is cited for reports of people north of Scythia “falling asleep” for half a year, and Epimenides is mentioned for a story of yearly cave-like cycles. More recent references include Northern Russia accounts of people entering a state described as sleeping for half a year when food is unavailable.

The case for a human hibernation-like state rests on bone pathology. During hibernation, animals accumulate pre-hibernating fat in summer, which supplies energy and nutrients—especially vitamin D. Vitamin D is tied to calcium regulation and parathyroid hormone activity, which can erode bone. In the Atapuerca skeletons, the researcher points to histological lesions consistent with hyperparathyroidism: trabecular bone appears “tunneled” or eroded under microscopic examination. A second line of evidence is rickets (described as evidence of vitamin D deficiency), argued to be absent in other cave skeletons because those populations presumably entered and exited caves rather than staying for months.

The bone record is presented as unusually diagnostic because the lesions are not treated as generic disease markers but as patterns expected from poorly tolerated hibernation physiology. The Atapuerca site is described as exceptionally rich—thousands of bones from at least 19 individuals—allowing repeated observation of these features.

Additional support comes from bone growth patterns. Hibernation is said to halt bone formation during metabolic slowdown, producing “gaps” and stratified zones of bone deposition separated by empty intervals. The researcher compares these to growth arrest markers seen in hibernating animals, arguing that the human pattern is distinctive: not just lines of arrested growth, but whole zones of missing deposition.

Finally, the discussion extends beyond paleontology. Modern experiments are cited as showing that humans can be induced into hibernation-like states via medical interventions that lower metabolic and cardiovascular activity. For spaceflight, the proposed benefit is reduced radiation damage: hibernation is framed as keeping DNA strands more closed, limiting cosmic-radiation-induced faults. The practical goal becomes making hibernation medically controllable—maintaining vitamin D and other hormonal balance—so astronauts could endure multi-year missions. The researcher’s estimate for the Atapuerca hibernation duration is roughly four months, possibly up to eight, based on the timing implied by the bone growth gaps.

Overall, the argument is that multiple independent bone-based signals—hyperparathyroidism, rickets, and growth arrest stratification—converge on a months-long, darkness-associated metabolic shutdown, with downstream relevance for medicine and space travel.