For 20,000 years, the bones from dozens of mammoths have held together in a large structure constructed by ancient humans during the European Ice Age. Now, archaeologists digging below the Earth’s surface are illuminating the lifestyles of our ancient relatives during times of scarcity.

Kostenki 11 is a well-known archaeological site located about 500 kilometers (310 miles) south of Moscow. Here, archaeologists with the University of Exeter unveiled a 9-by-9-meter (30-foot) circular feature constructed almost entirely of large mammoth bones used to house ancient people during the last ice age, which began in northern Europe around 75,000 years ago and ended around 18,000 years ago. Climate reconstructions of the time suggest that summers in the region were short and cool while winters were long and cold, often seeing temperatures of -20°C (-4°F) and colder.

Altogether, the site represents a “rare example of Palaeolithic hunter-gatherers living in a harsh environment” where survival was difficult and resources scarce. Many groups of ancient people left the region when temperatures plummeted, creating large bone structures along the way to warmer climates. But what might have set Kostenki 11 apart from other potential stops?

“One possibility is that the mammoths and humans could have come to the area on masse because it had a natural spring that would have provided unfrozen liquid water throughout the winter – rare in this period of extreme cold,” said study lead Dr Alexander Pryor in a statement.

There are around 70 known similar structures in Ukraine and the west Russian plane, but Kostenki 11 is likely one of the oldest features in the region.

"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,” said Pryor. “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."