Why did Ice Age people paint animals deep inside caves?

Nobody knows for certain, and that is the honest answer. What we do know is striking. In September 1940 an 18-year-old named Marcel Ravidat found a hole left by an uprooted tree, in France, and his dog investigated it. The cave behind it holds paintings of animals. Today the Lascaux paintings are usually dated to between 17,000 and 22,000 years ago, and the cave was painted with mineral pigments: ochre, hematite, manganese.

The animals tell a puzzle. Painters at Lascaux left mostly reindeer bones behind, yet horses are the most common animals on the walls, and only one reindeer appears. Chauvet cave, in the Ardèche, adds another surprise: its walls show cave lions, leopards, bears and hyenas, not only grazing animals.

Scholars have offered rival answers, and none has won. Early in the 20th century, Salomon Reinach and Henri Breuil read the pictures as hunting magic, a way to ensure a plentiful hunt. David Lewis-Williams, drawing on studies of living hunter-gatherers, proposed that shamans went into the dark, entered a trance and painted what they saw. R. Dale Guthrie suggested that many images are the work of adolescent males. Specialists also warn that a reader's own beliefs can colour the interpretation.

What the evidence does suggest is how closely they watched. A 2012 study found that cave artists drew the gait of four-legged animals more accurately than modern artists do.