Correcting and standardizing biometrical deformation in palaeolithic hand stencils: an experimental approach for age and sex determination

Hand representations are among the most significant and widespread motifs in Palaeolithic rock art, and they have long been regarded as a valuable source for investigating biological and social aspects of prehistoric communities, such as age, sex, or individual identity. However, morphometric analysis of these representations presents important methodological challenges due to dimensional alterations introduced during their creation. These deformations hinder direct comparability between archaeological hands and modern anatomical samples, potentially affecting the interpretation of biological variables. The aim of this study is to identify, quantify, and standardize the dimensional deviations produced by negative and positive hand execution techniques, explicitly considering the orientation of pigment application. To this end, 33 scanned anatomical hands and 198 experimental replicas, blown and pressed onto rock surfaces, were analysed across five primary orientations (frontal, up, down, left, and right). Metric measurements were performed on photogrammetric models and compared with the original scans obtained using a contact laser scanner. The results show that negative hands systematically produce outlines larger than the original anatomical model, while positive hands exhibit a general reduction in dimensions. Additionally, specific deformation patterns were identified for each orientation, particularly in the fingers. Based on these data, an average deformation index was defined, allowing for the correction and standardization of archaeological measurements. This approach improves analytical comparability and provides a tool applicable to morphometric studies of Palaeolithic rock art.