Rock art manufacture as a signal: an experiment and evaluation of the costliness of petroglyph production

This study evaluates the potential of petroglyph manufacture and the resulting\ud imagery as a costly signal by analyzing how well it conforms to the conditions of\ud Costly Signaling Theory (CST), particularly to the assumption of costliness. CST attempts\ud to explain how seemingly wasteful behavioral and morphological signals can\ud evolve provided that these signals honestly advertise the underlying qualities of the signaler\ud to an observer. One way that honesty can be ensured is if the signal imposes some\ud sort of cost on the signaler. To ascertain the costs associated with petroglyph manufacture,\ud an experiment was conducted using open-circuit indirect calorimetry to obtain accurate\ud measurements of energetic expenditure. Subjects created a number of standardized\ud petroglyph images using stone tools while instrumented to a metabolic cart to measure oxygen consumption and carbon dioxide production, from which energetic expenditure\ud is derived. Two methods of petroglyph production were tested, including indirect\ud pecking and direct pecking. A thorough analysis of the results of this experiment,\ud followed by a brief examination of other factors that may contribute to energetic expenditure,\ud indicates that petroglyph manufacture does not meet the costliness condition of\ud CST. The results also indicate that there is no significant difference in the energetic expenditure\ud of petroglyph production using the direct pecking method versus the indirect\ud pecking method. Additionally, a mathematical technique was developed that can be\ud used by researchers to estimate the energy expended during the production of any given\ud petroglyph encountered in the field.CSU, Chic