Neandertal use of fire is a highly debated topic, particularly the question of the extent to which these hominins were dependent on fire and how they used fire in their adaptations. To address this, our project focused on Layer 8 at the site of Pech de l'Aze IV in southwestern France. This layer has evidence for multiple burning events in the form of ashy layers, burned bones, and burned stone artifacts. However, individual hearths are usually poorly visible with the naked eye and thus cannot be individually excavated and analyzed using traditional archaeological methods. To overcome this limitation, we developed a methodology that incorporates meticulous, high-resolution, microstratigraphic excavation with 100% sampling, digital recording, and new software programs to allow us to capture the entirety of the contents and sediments from Layer 8.

Over our four-year project, we removed 10 intact blocks of Layer 8 sediments and transported them to our laboratory, where 6 were excavated (Figure 1: laboratory excavation stations). Three blocks were reserved for geoarchaeological analysis (including how each microstratigraphic layer was formed) and archaeomagnetic analysis; one block is maintained as a reference that is stored with all excavated materials. Each individual microstratigraphic layer was systematically described according to their lithostratigraphic attributes (Figure 2: Block 05 microstratigraphy) and these characteristics guided how the excavation of each Layer 8 block proceeded. Our software allowed us to use Microscribes in lieu of total stations to record the 3D position of all excavated materials (e.g., animal bones, stone artifacts, natural stones, excavated sediments) as if we were excavating at the site itself (Figure 3: point provenienced Layer 8 materials from three excavation blocks placed in 3D at the site). Each sediment block was photographed prior to and during excavations so that digital models of each could be constructed. The blocks were excavated in the form of several hundred, tiny 10 x 10 x 0.5 cm sections that were each point provenienced (3D position within the site grid) with a Microscribe. The sediment from each of these small sections was collected in a glass vial using a specially designed vacuum system (Figure 4: meticulous excavation at a laboratory station); the location of the vial-collected sediments was positioned in 3D space using a Microscribe.  All materials (animal bone, stone tools, natural stones) larger than 0.7 mm from each of these excavation contexts were analyzed, and observations included whether these materials were burned. The resulting 1,383 sediment-filled glass vials (ca. 50 ml each) are stored in a freezer to prevent degradation of the materials.

Because we were able to recover and store everything from each sediment block, we have detailed data that can be used to identify areas of individual hearths within Layer 8. For example, 5-gram subsamples of sediment from the same glass vial (strategically selected glass vial samples) are sent to various specialists who study evidence of the past presence of fire. These include analysis of phytoliths (opaline plant cells), geochemical biomarkers (e.g., plant and animal lipids), geomagnetic properties, thermoluminescence (heated minerals), Fourier transform infrared spectroscopy (FTIR; spectral data from organic and inorganic compounds), and micromorphology (sediment thin sections). We can then combine the results of each analysis with information from the examination of burned stone tools, burned animal bone, and geoarchaeological observations to isolate the boundaries of individual hearths or burned zones within Layer 8, including those not visible to the naked eye in the field or in the blocks themselves. These results give us information about how Neandertals made and used fire, as well as specific aspects of their pyrotechnology, such as temperature of burning, the type of fuel used, and the duration of individual fire events during the time represented by Layer 8.

The project incorporates the analyses produced by many different specialists; as yet we do not have comprehensive results from each of them. However, preliminary results of micromorphology, archaeomagnetism, FTIR, and thermoluminescence suggest specific loci of past burning events in the Layer 8 sediment blocks.

Last Modified: 05/31/2023
Modified by: Deborah I Olszewski