Art in time. Diachronic rates of change in the decoration of bone artefacts from the Beagle Channel region (Tierra del Fuego, Southern South America)

This paper explores the differential rates of diachronic change developed by diverse features of portable art in southern Tierra del Fuego. It is argued that decorative designs and techniques, which simultaneously constitute each decorated artefact, had asynchronic rates of change throughout the archaeological sequence. Results indicate that: (I) decorated harpoon points (1) had a broader and more complex design repertoire which entailed a higher labour investment and showed a faster rate of change than beads, due to a greater individual input in their decoration, (2) were richly decorated in spite of their high risk of loss/fracture, yet their decoration was concentrated in the early period of the archaeological sequence and then decreased in time due: a) to such loss/fracture risk, which jeopardised the labour invested in their decoration, (b) to a relative decrease in pinniped hunting which might have reduced the socio-economic and symbolic value of harpoons; (II) decorated beads (1) had a simpler and more standardised design repetoire which entailed a lower labour investment and showed a slower rate of change than harpoons, due to a stricter process of teaching/learning or imitation during their production and a collective way of ornamentation during their display, (2) increased with time and have been decorated during the three periods of the archaeological sequence due to: (a) their lower risk of loss/fracture, which did not endanger the labour invested in their decoration, (b) their social function as a shared form of ornamentation; (III) decorative techniques had a slower rate of change than decorative designs throughout the archaeological sequence due to their differential instrinsic variability potentials.