What helped our ancestors survive freezing winters?

Our primitive ancestors really had a hard time with harsh winters. In severe frosts, the only thing that helped them survive is a constant source of heating, fire, which they tried to maintain around the clock. Also in winter, ancient people took refuge in caves or primitive dwellings, which provided some protection from wind and precipitation. To warm the dwelling, furs and skins of killed animals were used, and fur clothes were made from them, which also helped our ancestors to maintain their existence.