Many animals hibernate for the winter. They stock up on food and hide away in a hole or cave to escape the snow and cold. Scientists now believe early human beings may have hibernated too. The scientists looked at the fossils of bones from our early ancestors who lived around 430,000 years ago. The bones were found in a site in the north of Spain. The scientists are experts in studying fossils and ancient bones. They say that the cuts and other signs of damage on the bones they examined are similar to those on bones of animals who hibernate, like bears. They also say that early humans may have hibernated to escape the extreme cold. Winters were much colder hundreds of thousands of years ago.

The scientists looked at the bones of several dozen humans. Scientist Antonis Bartsiokas said there is evidence that early humans slowed down their metabolism so they could survive longer in winter without food. However, humans could not slow their metabolism like a bear. Bears can wake up after months of hibernation and their body will be the same as when they went into hibernation. The bones of the early humans showed people suffered health problems because of hibernation. Many of the problems were caused by a lack of vitamin D, which we get from sunlight. This can make our bones weaker. The researchers said: "We have to emphasise that hibernations are not always healthy."