Date Published: March 14, 2019
Publisher: Public Library of Science
Author(s): Thegn N. Ladefoged, Caleb Gemmell, Mark McCoy, Alex Jorgensen, Hayley Glover, Christopher Stevenson, Dion O’Neale, Peter F. Biehl.
Over the span of some 700 years the colonizing populations of Aotearoa New Zealand grew, with subsequent changes in levels of interaction and social affiliation. Historical accounts document that Māori society transformed from relatively autonomous village-based groups into larger territorial lineages, which later formed even larger geo-political tribal associations. These shifts have not been well-documented in the archaeological record, but social network analysis (SNA) of pXRF sourced obsidian recovered from 15 archaeological sites documents variable levels of similarity and affiliation. Three site communities and two source communities are defined based on the differential proportions of obsidian from 13 distinct sources. Distance and travel time between archaeological sites and obsidian sources were not the defining factors for obsidian source selection and community membership, rather social considerations are implicated. Some archaeological sites incorporated material from far off sources, and in some instances geographically close sites contained material from different sources and were assigned to different communities. The analytical site communities constitute relational identifications that partially correspond to categorical identities of current Māori iwi (tribal) territories and boundaries. Based on very limited temporal information, these site communities are thought to have coalesced sometime after AD 1500. By incorporating previously published and unpublished data, the SNA of obsidian artefacts defined robust network communities that reflect differential levels of Māori interaction and affiliation.
The Polynesian colonists who settled New Zealand some 700 years ago  brought with them cultural conceptions of chiefdoms based on genealogical affiliation and territoriality . It has been suggested that the initial settlers lived in relatively autonomous villages  , and over several centuries these groups grew and formed geographically larger social units referred to as hapū . Genealogical and historical evidence suggests hapū membership was organized through kinship and spatially referenced to particular rohe (territory). At certain times and places hapū were dynamic and non-exclusive in nature . Although there was considerable variation, historic evidence suggests hapū affiliation provided access to resources, exchange opportunities, and security. By the 18th century historic evidence suggests hapū had often coalesced into larger social groups known as iwi  . Iwi affiliation potentially offered greater security against aggressors, but competition and infighting among aligned hapū was also common. While some of these social transformations are well attested in recorded oral traditions and historical accounts, they are not well documented in the archaeological record. To investigate changes in Māori interaction and affiliation we focus on tracing the spatial and temporal distribution of artefacts made of obsidian, an important stone resource that was used for a variety of tools  .
The combined data set comprises 2404 obsidian artefacts from 13 distinct sources recovered from 15 archaeological locations (Table 1; Fig 1; S1 Table). In nearly all cases these locations correspond to a single site number in the New Zealand Archaeological Association’s geodatabase of archaeological sites (www.archsite.org.nz), and we use the term site to refer to these locations. The temporal associations of the sites vary, and for 13 of these, we determined whether the assemblages from the sites likely pre or post-date AD 1500 based on the reported radiocarbon dates (see Table 1, and     ). The largest assemblage from a site, in terms of the number of artefacts, is Ponui Island with 565 artefacts, while the sites with the smallest assemblages are Taputiketike and the Sundae site, with 20 and 22 artefacts, respectively. As noted above, Mayor Island was often a major source of obsidian found in archaeological sites, and is by far the dominant source of material in the data set, with 915 artefacts, almost twice the number of the next most prolific source; Kaeo with 501 artefacts. The rarest sources, Rotorua, Taupō, and Tairua contribute only two, two, and five artefacts, respectively.
Peeples’  recent archaeological analysis of social networks in the American Southwest distinguishes between relational and categorical identification. These are two non-mutually exclusive modes of social identification that were created and maintained through differential processes. Relational identities were the result of networks of interpersonal interaction, created by direct and indirect connections between people. These identities did not involve explicit group membership or social roles, rather were often the result of interactions and exchanges of material culture. In contrast, categorical identification involved individuals explicitly identifying with others as members of larger groups. Membership in these groups could be consciously symbolized with material culture, with visually strong material being particularly affective. Peeples  suggests that dense relational networks of interaction were more susceptible to the creation of categorical identification, and in particular contexts the two could coalesce. The social network analysis of Aotearoa New Zealand obsidian artefacts provides insights into the relational and categorical connections of Māori identity.
Network analysis has identified discrete site and source communities on the basis of the composition of artefact assemblages and produced measures of the relative strengths of the relationships between them. The robust patterning of obsidian source frequency at archaeological sites does not directly correspond to geographical considerations. The source communities associated with these site communities are also not geographically close. Notably, while geographic distance influenced assemblage source compositions at some archaeological sites, divergence from the principles of acquiring material from the closest sources, or within small, local procurement areas, provides indications of social considerations. Sites within the Northland Site Community A were located close to each other and had similar compositions of artefact assemblages, as was the case for some sites within Site Community B and Site Community C. However, some sites within Site Communities B and C are located close to sites in the other community, yet contained very different compositions of source material in their artefact assemblages. This would suggest that people living in these relatively close locations had differential interaction levels, mobility patterns or procurement networks that were influenced by social considerations as opposed to purely least-cost geographic distances. While the temporal dimension of the spatial patterning is insecure due to small sample sizes, the community distinctions between sites that were geographically close was only identified when late period sites (post-AD 1500) were included in the analysis. Some of the site communities correspond to some boundaries of contemporary iwi rohe. We suggest that the relational identities associated with site community zones of interaction were significant in the development of iwi and hapū categorical identification. Future work on increasing sample sizes and refining chronological associations, possibly through the use obsidian hydration dating, will help clarify these and other aspects of Māori social affiliation.