Why are they so reluctant to use it? Mainly because they think that rock art pictures are not datable and consequently that one does not know the page of faunal history to which these documents relate. However, this is incorrect. In the Sahara, as elsewhere, rock art can be classified into "schools" that can be dated, admittedly in a crude way and inevitably with an important margin of uncertainty. Once this margin is known and accepted, observations and inferences become possible.