Animals stock up on food and hibernate for the winter. They escape the snow and cold in a cave or hole. Scientists think early humans may also have hibernated. The scientists looked at the bones from our ancestors who lived 430,000 years ago. The bones were found in Spain. The scientists are experts in studying ancient bones. They say that cuts and other signs of damage on the bones are similar to those on bones of animals who hibernate. They also say that early humans may have hibernated to escape the extreme cold. Winters were much colder hundreds of thousands of years ago.
A scientist said there is evidence to show early humans slowed down their metabolism. This was so they could survive longer in winter without food. However, humans could not do this like a bear. Bears can wake up after months of sleeping and their body will be the same as before they went into hibernation. The bones showed hibernation caused early humans health problems. Many of these were because of a lack of vitamin D, which we get from sunlight. This makes our bones weaker. The scientist said: "We have to emphasise that hibernations are not always healthy."