Broken ostrich eggshells are commonly found in Middle Stone Age sites of southern Africa, presumably collected for food consumption, and later used as artefacts. At Diepkloof Rock Shelter, Middle Stone Age inhabitants used ostrich eggshells as a medium to convey abstract depictions. Since 1998, excavations at Diepkloof have recovered 408 engraved pieces of ostrich eggshells. The study of these shows that Diepkloof inhabitants applied a restricted set of geometric engraving patterns, with the dominance of 2 main motifs, one using a hatched band and the other sub-parallel to converging lines. These motifs coexisted, but shifted in frequency toward the latter through time. Together with evidence that ostrich eggshells were used as containers, these patterns support the hypothesis that engravings were made with respect to clear but flexible social conventions and were part of a complex system of visual and symbolic communication. Since our last report (Texier et al., 2010), a few engraved pieces have been found in lower stratigraphic units, expanding substantially the time-range of the engraving practice on ostrich eggshells at Diepkloof. The earliest engravings appear at the end of the Early Howiesons Poort phase, but become numerous only during the Intermediate and Late phases of the Howiesons Poort. The collection from Diepkloof is presently unique and likely underlines the existence of regional traditions within the Howiesons Poort. Interestingly, and significantly in our view, the engraving disappears at the same time as the Howiesons Poort technology. We argue that this disappearance may reflect a modification in the way late Middle Stone Age inhabitants interacted with one another.