What does size mean? Searching for reasons for small tools in Navalmaíllo Rock Shelter by experimenting with quartz knapping from the Lozoya river Valley (Madrid, Spain)

Abstract

Navalmaíllo Rock Shelter is one of five Middle Palaeolithic sites located in the karstic Calvero de la Higuera hill of Pinilla del Valle in the Lozoya river valley in the Central System of the Iberian Peninsula at c. 1100 m a.s.l. The intra mountain valley is an Hercinic pop-down structure covered by preserved Upper Cretaceous dolomites where karst systems are formed. The surrounding pop-up structure of Alpine orogeny gneisses and granites comprises the Guadarrama Mountain Range of the Central System. Level F of Navalmaíllo Rock Shelter has a Neanderthal occupation between MIS 5a – early MIS 4 characterized by an abundance of lithic industry in quartz (c. 80% of total assemblage) with a strong tendency towards microlithism. Use-wear analyses performed on quartz samples point toward the versatility and intensive use of micro-tools. Reasons for small tools and intense reduction of lithics in the Middle Palaeolithic are usually interpreted as economic or cultural adaptations, functional reasons or limitations such as - economic response to scarce raw materials of good quality, ramification of production by recycling existent tools into cores of new generation supports, adaptation to raw material constraints (support format and mechanical properties), a cognitive development linked to learning processes or cultural differentiation. In the case of the Lozoya river valley, quartz is the most abundant raw material. To understand the reasons for the intense exploitation of this raw material and microlitization processes we did: 1) an intensive survey of the valley to record the availability of quartz, nodules format, and physical properties, 2) an experimental analysis using different knapping methods (bipolar, discoid, Levallois recurrent centripetal and preferential flake) using quartz nodules from the Lozoya valley. With this study we aim at understanding the transformation processes by knapping quartz following the most common reduction techniques of the Navalmaíllo Rock Shelter assemblage, the non-common (and almost inexistent such as Levallois) and analyse the knapping products. It is known that raw materials mechanical properties are important to understand technological adaptations within the chaîne opératoire. Mechanical constraints, together with a lower level of dexterity are assumed to be determining factors for the microlitization of quartz tools in older chronologies. Through the analysis of quartz properties and its behaviour when submitted to different knapping methods we hope to better understand Neanderthal technological adaptation to the resources of the Lozoya valley and tackle the reasons for the abundance of small tools in Navalmaíllo Rock Shelter.