Is loading a significantly influential factor in the development of lithic microwear? An experimental test using LSCM on basalt from Olduvai Gorge

Lithic microwear develops as a result of abrasive friction between a stone tool’s working edge and the surface of a worked material. Variation in the loading (i.e. force) applied to a stone tool during its use alters the amount of friction created between these two materials and should subsequently affect the level of any wear accrued. To date, however, no comprehensive account of the interaction between variable working loads and wear development has been undertaken. If such a relationship does exist, it may be possible to calculate the loading levels applied to stone tool artefacts during their use. Here, we use 30 basalt flakes knapped from raw materials collected in Olduvai Gorge, Tanzania, in a controlled experimental cutting task of standardized duration. Loading levels are recorded throughout with each flake being used with a predetermined load, ranging between 150 g and 4.5 kg. Laser scanning confocal microscopy (LSCM), coupled with the relative area (Srel) algorithm, is used to mathematically document the surface texture of the flakes to determine whether variation in loading does in fact significantly affect the amount of wear on the flake surfaces. Results indicate that working load does play a role in the development of lithic microwear; however, its interaction with other variables, including the naturally rough surface of basalt, may reduce the likelihood of its accurate determination on tools recovered from archaeological deposits.