Determining the reduction sequence of Hawaiian quadrangular adzes using 3D approaches: a case study from Moloka'i

Hawaiian adze manufacture requires a great deal of skill and undoubtedly required long apprenticeships to achieve the finesse seen in many finished prehistoric adzes. Despite the presence of more than two dozen adze quarries in Hawai'i, and previous attempts at replicating adze preforms and positing reduction sequences in Polynesia, there is no detailed study that clearly defines the steps and stages of quadrangular adze preform manufacture (the most common form in Hawai'i), and the resulting characteristic debitage. In this paper we examine the sequence of adze production for a population of 109 adzes from Moloka'i, documenting the transition from blanks to preforms to the finished objects that were transported away from quarries. Reduction intensity is measured using the Scar Density Index (Clarkson, 2013) calculated from 3D scans. We document the sequence of cumulative additions of characteristic features to adzes (e.g. bidirectional edges, bevel, poll and tang) as reduction intensity increases. We also note the reasons for adze rejection at each stage of reduction. Our study provides the first detailed analysis of adze reduction in Polynesia facilitated and standardised by 3D scanning technology. Hopefully, it will serve as a useful benchmark for objectively and systematically comparing adze technology in other parts of Hawai'i and across Polynesia, leading to a better understanding of regional and temporal variation in adze technology.