The environment in which some of humanity’s first–and still best–works of art, in the cave of Lascaux nearly thirty thousand years ago, is described here by Randall White:

Plant materials, especially wood, would have been important fuel for cooking, heating, and light. Again, the excellent preservation at Lascaux indicates that certain species of trees and shrubs were sought, especially as fuel for bonfires and torches and as wicks for the stone lamps used to provide light in the cave. The charcoal recovered from Lascaux comes primarily from juniper bushes. Their wood provides long-burning aromatic fuel because of its high resin content.

      People relied primarily on fireplaces for warmth in cold weather. These take a surprising number of different forms that vary from period to period and from region to region. They vary from very small (a few centimeters in diameter) to immense (as much as two meters in diameter), and from cobble-lined structures to simple pits. Some were dug into the ground; others were not. Where available, wood served as the primary fuel. However, bone scraps (which make excellent fuel because of their fat content) were also used, especially in periods and regions lacking abundant wood.

      Cooking included techniques for boiling. Upper Paleolithic sites often have pits full of cobbles fractured by temperature change in the same way that a glass bowl might break if removed from the oven and placed in the refrigerator. To boil water, people simply took red-hot cobbles from a fire and dropped them into a skin-lined pit full of water.

      Prehistoric people developed strategies to reduce their fuel requirements as many people have done since (including ourselves in recent years). For example, in southwestern France, 75% of known Upper Paleolithic sites are located on south-facing slopes and at the bases of south-facing cliffs. This familiar strategy is based on the recognition that, at European latitudes, south-facing embankments and cliff faces take on solar heat during the day and give it off slowly at night.

– Randall White, Prehistoric Art: The Symbolic Journey of Humankind, 35