Painting Altamira Cave? Shell tools for ochre-processing in the Upper Palaeolithic in northern Iberia

Much of our knowledge of the symbolic world of Upper Palaeolithic hunter-gatherers is based on the study of the graphic representations found in Western European caves. However, to date, few studies have been conducted on rock art apart from chronological and stylistic characterisation. Altamira Cave (northern Iberia) is characterised by an outstanding rock art ensemble, whose representations cover practically the whole Upper Palaeolithic. The site is equally important for the rich Upper Palaeolithic deposits in the cave entrance, which contain large shell assemblages. Traditionally, the presence of shells in hunter-fisher-gatherer settlements has been interpreted as part of the diet and/or the symbolic world (through the creation of ornaments) of these groups, regardless of their possible use as an instrument. In this paper we utilise use-wear methodology, chemical analysis and analytical experimentation to verify the initial hypothesis that shells in the archaeological deposits of Altamira were used to obtain the ochre powder utilised to produce the magnificent and diverse rock art ensemble in the cave. The results provide new information on the process of obtaining pigments for the realisation of paintings and confirm that the use of shells to obtain ochre was a systematic activity throughout the whole study period. Finally, our conclusions support the explanatory model that highlights the role played by marine resources for Upper Palaeolithic human populations.