Here it may be asked, What is to be thought of the already-mentioned pebble-markings from the Mas-d'Azil Cave at the close of the Old Stone Age? If they are truly phonetic, then we must suppose that palaeolithic man not only invented an alphabetic writing system, but did this right off by intuition, as it were, without any previous knowledge of letters. At least no one will suggest that the Dordogne cave-dwellers were already in possession of pictographic or other crude systems, from which the Mas-d'Azil "script" might have been slowly evolved. Yet E. Piette, who groups these pebbles, painted with peroxide of iron, in the four categories of numerals, symbols, pictographs, and alphabetical characters, states, in reference to these last, that 13 out of 23 Phoenician characters were equally Azilian graphic signs. He even suggests that there may be an approach to an inscription in one group, where, however, the mark indicating a stop implies a script running Semitic-fashion from right to left, whereas the letters themselves seem to face the other way[118]. G. G. MacCurdy[119], who accepts the evidence for the existence of writing in Azilian, if not in Magdalenian times, notes the close similarity between palaeolithic signs and Phoenician, ancient Greek and Cypriote letters. But J. Dechelette[120], reviewing (pp. 234, 236) the arguments against Piette's claims, points out in conclusion (p. 320) the impossibility of admitting that the population of Gaul could suddenly lose so beneficial a discovery as that of writing. Yet thousands of years elapse before the earliest appearance of epigraphic monuments. [Illustration: EVOLUTION OF THE SUMERIAN CUNEIFORMS.]