Blind tests of inter-analyst correspondence and accuracy in the identification of cut marks, percussion marks, and carnivore tooth marks on bone surfaces

We show through blind tests that marks inflicted on bone surfaces by carnivore teeth, hammerstone percussion, and metal knife cutting and scraping can be distinguished with near perfect reliability without scanning electron microscopy or consideration of only conspicuous marks. Using low-cost and high-volume hand lens and low-power light microscope techniques, we determined the presence or absence of conspicuous and inconspicuous marks with 97% three-way correspondence, and diagnosed marks of known origin to actor and effector with 99% accuracy. Novices with less than 3 h training on control collections correctly diagnosed 86% of classic but mainly inconspicuous marks. Novices spending several more hours studying control specimens elevated their diagnostic accuracy on morphologically representative marks to near-expert levels of 95%. Our results show that published cautions about mimicry among cut marks, percussion marks, and carnivore tooth marks are overstated. All types of marks examined can be identified reliably, regardless of conspicuousness. As such, fully standardized comparisons of mark frequencies can be drawn among assemblages, even those documented by different analysts. However, such robust interpretations can be attained only if analysts base diagnoses on (a) a firm familiarity with bones marked under strictly controlled conditions, (b) the systematic application of published morphological and contextual criteria, and (c) the use of prescribed low-power magnification techniques.