The painted caves of Lascaux in the Dordogne region of France are one of the most famed monuments of Ice Age art. Dating back about 17,000 years, the great Hall of the Bulls and its adjacent chambers proved so popular with visitors that a generation ago the cave had to be closed to save the paintings from encroaching mould. A replica, Lascaux II, was built nearby and has proved equally popular.

One thing that strikes the visitor is the exuberance of the compositions, with hundreds of animals, including bison, horses and deer, parading along the walls and ceilings, often overlapping. A big problem in sorting out possible groupings of animals, and possible motives for painting them, has been the issue of contemporaneity — what was painted when?

A recent study by scientists at the Louvre’s research and conservation laboratories has suggested one avenue of approach, by studying the chemical structure of pigments from the cave walls and ancient antlers from Palaeolithic sites. The presence of minuscule antler fragments in the paints may enable animal figures composed at the same time, using the same batch of paint, to be isolated and then studied apart from neighbouring depictions.

Earlier paint analyses had detected phosphorus and calcium, suggesting the presence of crushed bone material: whether this was the result of adding bone powder as an extender for the paint, or the use of bone tools for applying it, was not clear. Writing in the journal Archaeometry, Céline Chadefaux and her colleagues note that bone, ivory and antler have similar compositions and can be studied using the same techniques.

Seven antler specimens from Palaeolithic sites in the Dordogne region were examined, together with modern control samples of antler.

Sixty-three paint samples from the Hall of the Bulls and the Axial Chamber of the Lascaux cave, 18 of them with calcium and phosphorus present, were also analysed.

The use of TEM-EDX (transmission electron microscopy coupled with an energy-dispersive X-ray system) showed that antler could be distinguished from the other two substances because tiny needle-shaped crystals of hydroxlapatite were present; this feature persisted through the loss of organic matter over the millennia and the infiltration of various element from the burial soil, and, Chadefaux’s team reports: “It is therefore possible to distinguish antler apatite crystals from bone and ivory crystals on the nanometre scale.”

Calcium and phosphorus were noted in paint from a red cow on the right wall of the Hall of the Bulls, a brown horse on the left wall of the same room, and a red-and-black horse in the axial chamber, three of the most striking animal portrayals at Lascaux. The colours came from mixtures of haematite with other minerals, and antler apatite crystals were also noted.

Whether these came from powdered antler extender or from a stirring rod could not be determined, and it is also known that antler artefacts were carved by the cave users.

On a balance, the presence of the antler, which seems from its scarcity in the paint samples to have been from a single short period of activity about 17,000 years ago, can be used an an indicator of a group of paintings that were created contemporaneously, and is thus “a tracer of a specific ornamentation phase of the cave”, the team concludes. Similar discovery of unusual extraneous materials in other cave pigments might then enable different episodes in the creation of Lascaux’s rich inventory of art to be teased out.

Archaeometry 50: 516-534.