Stylistic variability of stemmed obsidian biface tools on Easter Island

The bifacially-flaked stemmed obsidian artifacts from Easter Island -known as mata’a -vary greatly in terms of the shape and form of their stems. The stem variability appears to be largely stylistic in nature as its variation does not affect the function of the tool and thus is free to change. Since performance is not a factor in structuring variation , patterns of similarity across stylistic classes of mata’a stem shape potentially reflect the effect of cultural transmission through time and across space. In order to generate hypotheses about the structure of transmission, we measured 135 complete mata’a that were collected during the 2006 CSULB archaeological field school to Rapa Nui. Using stylistic classes consisting of 7 dimensions, we performed cladistic, phenetic, seriation and correspondence analyses. We expect for the mata’a to show spatial similarity, due to the interaction structure of the prehistoric Rapa Nui populations. This would be seen as strong clusters of mata’a that correspond to areas of collection.