Mysterious bone circles consisting of hundreds of mammoths bones helped scientists understand how people survived the last ice age. According to a new analysis, the bones at one location in Russia were more than 20,000 years old.

25,000-year-old mammoth bone structure, Kostenki, Russia: 12.5 meters in diameter

The wall of the 30 ft building was constructed using a combination of 51 lower jaws and 64 individual mammoth skulls. There were also a small number of reindeers, goats, rabbits, dogs, red foxes, and arctic fox bones.

Researchers said the bones were most likely sourced from animal graveyards.

In the site, which is situated near the current village of Kostenki, some 500 km south of Moscow, an archeologist from Exeter University discovered remains of charred wood and other soft non-woody plants.

It indicates that people used to burn wood as well as bones for fuel, and the communities who lived there had learned where to forage for edible plants during the Ice Age.

Dr. Alexander Pryor, who led the study, said: “Kostenki 11 represents a rare example of Palaeolithic hunter-gatherers living on in this harsh environment.

“What might have brought ancient hunter-gatherers to this site?

“One possibility is that the mammoths and humans could have come to the area en masse because it had a natural spring that would have provided unfrozen liquid water throughout the winter – rare in this period of extreme cold.

“These finds shed new light on the purpose of these mysterious sites.

“Archaeology is showing us more about how our ancestors survived in this desperately cold and hostile environment at the climax of the last Ice Age.

“Most other places at similar latitudes in Europe had been abandoned by this time, but these groups had managed to adapt to find food, shelter, and water.”

The last Ice Age swept northern Europe between 75-18,000 years ago and reached its coldest and most severe state around 23-18,000 years ago.

Most communities fled the region, likely due to a lack of prey to hunt and scarce plant resources they depended upon for survival, the scientists said.

The bone circles, of which more than 70 are known to exist in Ukraine and the west Russian planes, were eventually abandoned as the climate grew colder and more inhospitable.

Archaeologists previously assumed the circular mammoth bone structures were used as dwellings, but the new study, published in the journal Antiquity, suggests this may not always have been the case.