New evidence and interpretation of subvertical grooves in eandertal teeth from Cueva de Sidrón (Spain) and Figueira Brava (Portugal)

Abstract

Interproximal tooth wear is caused by tooth-to-tooth rubbing that results in the formation of flat wear surfaces characterized by an intense pattern of enamel pitting caused by prism-plucking. The rate of wear of such surfaces depends on the forces involved in food processing and chewing. In some instances, the interproximal wear facets, mainly of molar teeth, show a number of subvertical grooves with a nearly vertical direction. These grooves are mostly present in Neanderthal teeth, but have also been described in some African fossil teeth and in European Homo heidelbergensis, as well as in several modern hunter-gatherer populations, such as Australian Aborigines. Subvertical grooves have seldom been attributed to taphonomic processes, although most probably they are caused by natural biomechanical processes during mastication of hard objects included in the diet. They have also been associated to acidic dietary habits given their radial disposition and their inter-digitalisation. The present study analyses the subvertical grooves observed in the Neanderthal dentition of Cueva de Sidrón (Spain). Comparisons are made with the similar interproximal grooves pattern observed in the Neanderthal specimen from Figueira Brava (Portugal) and some remains of H. heidelbergensis from Sima de los Huesos (Spain). Other cases have been described for the Neanderthal sites of Genay and Le Fate (France). The results obtained allow discarding a post-mortem origin of these structures, the most probable cause of the subvertical grooves being natural biomechanical chewing processes combined with some dietary habits indicative of hard plant foods ingestion.