Dating the Cassis Rufa Shell from the Mousterian Levels of the Grotte Du Prince, Monaco

Article excerpt

A fragment of Cassis rufa shell, in modern times a species of the Indian Ocean, was reliably reported from the deep Mousterian deposits excavated at the beginning of the century from the Grotte du Prince, Monaco. Because its known habitat is so distant and exotic, there has always been question about the specimen's authenticity. A radiocarbon determination shows it to be recent, and no evidence for long-distance movement of shell in the European Middle Palaeolithic.

In 1906, Boule (1906: 123) and Villeneuve (1906: 244) reported an unusual shell fragment among the faunal remains from one of the lowest hearths in the deep Mousterian deposits excavated from the Grotte du Prince, one of the Grimaldi Caves along the Mediterranean coast of Monaco. The excavations were conducted from 1895 to 1902 under the direction of Le Chanoine Villeneuve. The Mousterian deposits were contained in a talus cone that progressively filled the cavern almost to its 20-m height. Although the deposits at the entrance to the cave had been disturbed by railway and quarrying activities, the inner deposits were 'intact' and very voluminous. Five distinct hearth zones were identified in the interior; hearth D was the second from the bottom. It was from this hearth that the fragment of Cassis (Cypraecassis) rufa was reportedly excavated. In referring to this shell, Villeneuve (1906: 244) stated in his report that: 'Il n'y a pas de doute sur l'origine de cette piece, elle gisait dans le foyer D, par consequent tres bas'. However, in his report, Boule (1906: 123) wrote a long footnote expressing surprise at the recovery of this specimen from Mousterian deposits in Monaco, as it was not a Mediterranean species; the closest known habitat was the Aden coast and the Indian Ocean, implying long-distance transport at a very early time.

The implications of this find remain of considerable interest today, and some prehistorians have expressed scepticism about the Mousterian age of the specimen in present-day reflections similar to those of Boule (Renfrew 1986; Reese 1989; 1991; pers. comm.; D. Bar-Yosef pers. comm.). While the transport of shells and other materials (e.g. pyrites) up to 90 km from their source has been documented from Mousterian sites in France and the Levant, such transport was still relatively rare (O. Bar-Yosef 1989: 178; pers. comm.; D. Bar-Yosef 1989: 170; J.-M. Geneste pers. comm.; see also Hayden 1993). The distance of transport implied by the Cassis shell would have been most unusual for a Mousterian assemblage, and indeed far greater than anything else documented for the later Upper Palaeolithic and even Neolithic periods. It is difficult to reconcile such movement with our current understanding of Palaeolithic hunter/gatherer mobility and socio-economic organization.

Subsequent research has not added new information to resolve this difficulty. Malacologists agree on the identification, as the species has a very distinctive morphology, size and colouring. No closer present-day habitat has been identified (Abbott 1969), and it seems unlikely that a species from warm present oceans would have been found further north in the Pleistocene. It seems indisputable that the only possible means that the shell could have been deposited at the Grotte du Prince was via human transport.

The remaining question is the age of the sample, and fortunately that can be tested. The specimen itself is in the collections of the Musee d'Anthropologie Prehistorique de Monaco, and we received permission to photograph and remove a small portion for radiocarbon dating.

Radiocarbon dates on marine shells may be affected by two potential problems:

1 Exchange of the shell carbonate with carbonates in the ground water. In the calcareous terrain of southern Europe, ground-water carbonates are likely derived from the old calcareous rocks and modern biogenic and atmospheric carbon dioxide. Any exchange processes would thus make very old shell samples appear considerably younger, and very young shell samples appear somewhat older. …