The use of fire is a well-established human practice, at least from the Late Pleistocene. The variability in fuel type highlights complex practices regarding fire technology throughout this period. This contribution provides the organic signatures from fireplaces and is based on a set of experimental studies using different types of fuel, notably bone and/or wood. Soil layers affected by fire operation were compared with soils unaffected by heating and soils impregnated with unburned bone fat. The carbon content and lipid and bulk organic matter (OM) composition were determined through organic carbon measurement, gas chromatography–mass spectrometry (GC–MS), as well as TMAH (tetramethylammonium hydroxide)-assisted pyrolysis (py) coupled to GC–MS.