Dating the Cassis rufa shell from the Mousterian levels of the Grotte du Prince, Monaco.

Dating the Cassis rufa shell from the Mousterian levels of the Grotte du Prince, Monaco. A fragment of Cassis rufa shell, in modern times a species of theIndian Ocean, was reliably reported from the deep Mousterian depositsexcavated at the beginning of the century from the Grotte du Prince,Monaco. Because its known habitat is so distant and exotic, there hasalways been question about the specimen's authenticity. Aradiocarbon determination shows it to be recent, and no evidence forlong-distance movement of shell in the European Middle Palaeolithic. In 1906, Boule bouleDeliberative council in the city-states of ancient Greece. It existed in almost all constitutional city-states, especially from the late 6th century BC. In Athens the boule was created as an aristocratic body by Solon in 594 BC; later, under Cleisthenes, 500 members (1906: 123) and Villeneuve (1906: 244) reported anunusual shell fragment among the faunal remains from one of the lowesthearths in the deep Mousterian deposits excavated from the Grotte duPrince, one of the Grimaldi Caves along the Mediterranean coast ofMonaco. The excavations were conducted from 1895 to 1902 under thedirection of Le Chanoine Villeneuve. The Mousterian deposits werecontained in a talus cone that progressively filled the cavern almost toits 20-m height. Although the deposits at the entrance to the cave hadbeen disturbed by railway and quarrying activities, the inner depositswere 'intact' and very voluminous. Five distinct hearth zoneswere identified in the interior; hearth D was the second from thebottom. It was from this hearth that the fragment of Cassis(Cypraecassis) rufa was reportedly excavated. In referring to thisshell, Villeneuve (1906: 244) stated in his report that: 'Iln'y a pas de doute sur l'origine de cette piece, elle gisaitdans le foyer D, par consequent tres bas'. However, in his report,Boule (1906: 123) wrote a long footnote expressing surprise at therecovery of this specimen from Mousterian deposits in Monaco, as it wasnot a Mediterranean species; the closest known habitat was the Adencoast and the Indian Ocean, implying long-distance transport at a veryearly time. The implications of this find remain of considerable interesttoday, and some prehistorians have expressed scepticism about theMousterian age of the specimen in present-day reflections similar tothose of Boule (Renfrew 1986; Reese 1989; 1991; pers. comm.; D.Bar-Yosef pers. comm.). While the transport of shells and othermaterials (e.g. pyrites) up to 90 km from their source has beendocumented from Mousterian sites in France and the Levant Levant(ləvănt`)[Ital.,=east], collective name for the countries of the eastern shore of the Mediterranean from Egypt to, and including, Turkey. , suchtransport was still relatively rare (O. Bar-Yosef 1989: 178; pers.comm.; D. Bar-Yosef 1989: 170; J.-M. Geneste pers. comm.; see alsoHayden 1993). The distance of transport implied by the Cassis shellwould have been most unusual for a Mousterian assemblage, and indeed fargreater than anything else documented for the later Upper Palaeolithicand even Neolithic periods. It is difficult to reconcile such movementwith our current understanding of Palaeolithic hunter/gatherer mobilityand socio-economic organization. Subsequent research has not added new information to resolve thisdifficulty. Malacologists agree on the identification, as the specieshas a very distinctive morphology, size and colouring. No closerpresent-day habitat has been identified (Abbott 1969), and it seemsunlikely that a species from warm present oceans would have been foundfurther north in the Pleistocene. It seems indisputable that the onlypossible means that the shell could have been deposited at the Grotte duPrince was via human transport. The remaining question is the age of the sample, and fortunatelythat can be tested. The specimen itself is in the collections of theMusee d'Anthropologie Prehistorique de Monaco, and we receivedpermission to photograph and remove a small portion for radiocarbondating. Radiocarbon dates on marine shells may be affected by two potentialproblems: 1 Exchange of the shell carbonate with carbonates in the groundwater. In the calcareous calcareous/cal��car��e��ous/ (kal-kar��e-us) pertaining to or containing lime; chalky. cal��car��e��ousadj. terrain of southern Europe, ground-watercarbonates are likely derived from the old calcareous rocks and modernbiogenic biogenic/bi��o��gen��ic/ (-jen��ik) having origins in biological processes. biogenichaving the property of originating in a biological process. and atmospheric carbon dioxide. Any exchange processes wouldthus make very old shell samples appear considerably younger, and veryyoung shell samples appear somewhat older. 2 Since marine organisms obtain their carbon from the ocean, theradiocarbon ages of the organisms are apparently too old. In this case,that is not a problem, as the magnitude of this affect is seldom morethan a few hundred years, and the problem here is to determine whetherthe shell age is, or is not, many tens of thousands of years. The exchange problem is the primary difficulty. Our approach was toobtain a sufficiently large piece of the shell so that we could examineits microscopic structure and remove a portion from the interior. Thisportion would then be radiocarbon dated using the accelerator massspectrometry accelerator mass spectrometryn.Mass spectroscopy in which a particle accelerator is used to disassociate molecules, ionize atoms, and accelerate the ions. (AMS AMS - Andrew Message System ) method, with one of two anticipated outcomes: i a very young age, close to the time of excavation if the samplein some way reflects excavation problems, or ii an intermediate or apparently Mousterian age which wouldindicate that the sample was either truly of some antiquity or that ithad been contaminated by exchange. If the latter result were obtained, then we would have to dofurther work to establish the true age. To do this, we planned to use anew method for radiocarbon dating protein (Nelson 1991) which wouldyield an age not affected by carbonate contamination. The fragment removed for analysis (FIGURE 1) had approximatedimensions of 2 x 1 x 1 cm and weighed 2.5 g. Examination of thenewly-cut surface clearly showed that the shell interior remains inpristine condition. The surface is lustrous lus��trous?adj.1. Having a sheen or glow.2. Gleaming with or as if with brilliant light; radiant. See Synonyms at bright.lus and retains thebrownish-pink colouring for which the shell is named. Detailed,individual growth layering is clearly visible under the microscope. Ourimmediate impression was that the shell is remarkably well preserved ifit is indeed 50,000 years old. [CHART OMITTED] A small portion of the sample was cleaned in distilled water andplaced in an evacuated reaction vessel. Phosphoric acid was added, andthe first carbon dioxide released was pumped away, so that we would besampling only interior material. The subsequent [CO.sub.2] was collectedand converted into two portions of graphite for separate AMSdeterminations. These measurements were made in the normal fashion(Davis et al. 1990) at the Center for Accelerator Mass Spectrometry,Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory:see Lawrence Berkeley National Laboratory. (body) Lawrence Livermore National Laboratory - (LLNL) A research organaisatin operated by the University of California under a contract with the US Department of Energy. , USA. While the normal procedureis to determine the stable isotope ([delta][.sup.13C]) value for eachindividual sample, we have here assumed a value typical of marineshells. The uncertainty in so doing is at most a few decades, which isof no consequence to this study. The two ages obtained are given inTABLE 1. [TABULAR DATA OMITTED] The two measures obtained are self-consistent, giving a weightedaverage of 670 [+ or -] 50 Before Present. Can this be a contaminatedMousterian shell? It is highly unlikely. For a shell of true age40,000--50,000 years to have an apparent age of 670 years, > 90% ofits carbon must have been exchanged for carbon of Modern [.sup.14C]concentration. This is highly unlikely even if the shell could have beencontaminated by groundwater containing [.sup.14C] from nuclear weaponstesting, and in this case the specimen was collected a half-centurybefore the advent of nuclear fission fission,in physics: see nuclear energy and nucleus; see also atomic bomb. . Clearly, the shell is recent, notof Mousterian age. How recent? As discussed above, to obtain the true age we mustadjust the age obtained for the ocean-water effect. Using data on theapparent ages of recent (pre-bomb) shells from the Indian Ocean area (J.Southon pers. comm.) and the calibration provided by Stuiver et al.(1988), we obtain a possible calendrical age range for this sampleextending from about 1700 AD to the time of the excavation. Thus, the shell is not evidence for Mousterian long-range trade,but rather it appears to be an example of the problems inherent inarchaeological excavation. How could it have got into hearth D? The measured age provides only fuel for speculation. Cassis rufashells were traded into the Mediterranean during this time period; asVilleneuve (1906: 244) himself notes, 'C'est un morceau Mor`ceau´n. 1. A bit; a morsel.Noun 1. morceau - a short literary or musical compositionpiece - an artistic or literary composition; "he wrote an interesting piece on Iran"; "the children acted out a comic d'une grande coquille co��quille?n.A scallop-shaped dish or a scallop shell in which various seafood dishes are browned and served.[French, from Latin conch bien connue dans nos ports ou les marinsl'apportent de l'ocean Indien ou du Pacifique; Cassis rufa, lecasque rouge utilise en Italie pour la confection con��fec��tionn.A sweetened medicinal compound. Also called electuary. des camees'. How such an item would then find its way into the cave is open toconjecture. It may have been a prank. Even today, various objects thatare considered to be 'obvious' fakes are sometimes slippedinto the matrices of unsuspecting co-workers. Unfortunately, these jokesare not always evident to everyone involved, and once taken seriously byprominent investigators, it becomes difficult for perpetrators to admitresponsibility. Fortunately, with modern dating techniques, it has nowbecome possible to correct some of these distortions of ourarchaeological data. Acknowledgements. We are extremely grateful for the generouscooperation of the Musee d'Anthropologie Prehistorique de Monacoand for the kind assistance of Daniella Bar-Yosef, Henk Mienis and DavidReese. We thank N. Shackleton for critical comments and suggestions. Themeasurements and interpretations were undertaken at LLNL LLNL - Lawrence Livermore National Laboratory with the kindpermission of Jay Davis and the expert assistance of John Southon andother staff members. References ABBOTT, R.T. 1968. The helmet shells of the world (Cassidae), PartI, Indo-pacific Mollusca 2(9): 69--70. BAR-YOSEF, D. 1989. Late Paleolithic and Neolithic marine shells inthe southern Levant as cultural markers, in C. Hayes (ed.), Proceedingsof the 1986 shell bead conference, Rochester Museum and Science Center The Rochester Museum and Science Center, or RMSC, is a museum in Rochester, New York that features many exhibits related to science. These include AdventureZone, Expedition Earth, How Things Work, and the temporary traveling Dinosaurs exhibits. Research Records 20: 169--74. BAR-YOSEF, O. 1989. Upper Pleistocene cultural stratigraphy stratigraphy,branch of geology specifically concerned with the arrangement of layered rocks (see stratification). Stratigraphy is based on the law of superposition, which states that in a normal sequence of rock layers the youngest is on top and the oldest on the insouthwest Asia, in E. Trinkaus (ed.), The emergence of modern humans:154--80. 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