Understanding Neanderthal technological adaptation at Navalmaíllo Rock Shelter (Spain) by measuring lithic raw materials performance variability

Navalmaíllo Rock Shelter is an Upper Pleistocene archaeological site in the Lozoya River Valley (Madrid, Spain) with a quartz-based Mousterian lithic assemblage. To understand the reasons behind an intense use of quartz over flint and quartzite, a mechanical experiment was carried out. Flakes from flint, quartzite, and local quartz were tested under controlled conditions and quantifiable variables. The mechanical action consisted in a standardised linear repetitive cutting protocol over antler and pine wood. Results allowed to differentiate flake resistance between raw materials through mass and edge angle material loss statistics. Results also showed that the edges produced on flint are sharper allowing to create deeper cuts, but the thin working edges break more easily meaning that they would need a higher maintenance by retouch. Quartzite and quartz have similar performances, but quartzite suffers a more intense modification of the edge angle, while quartz edges present a higher endurance. When compared with flint, quartzite and quartz are more suitable for those tasks where heavier force is applied. Based on that, we concluded that there was no functional disadvantage in using a quartz-based toolkit. Therefore, the quartz assemblages recovered throughout the sequence of Navalmaíllo Rock Shelter show that it was intensely explored not just because of its availability in the landscape but also for its suitability to the development of the different activities taking place at Navalmaíllo Rock Shelter such as big sized herbivore butchering, for a long time span