Significance: Our paper evaluates a long-standing debate and examines whether the prehistoric population of Rapa Nui experienced a significant demographic collapse prior to European contact in AD 1722. We have used dates from hydrated obsidian artifacts recovered from habitation sites as a proxy for land use over time. The analysis suggests region-specific dynamics that include the abandonment of leeward and interior locations. These temporal land-use patterns correlate with rainfall variation and soil quality. This analysis demonstrates that the concept of “collapse” is a misleading characterization of prehistoric human population dynamics. As a result, we see our approach as useful in the study of other prehistoric societies for which a sudden demographic collapse has been proposed in prehistory.

On the island of Rapa Nui the Cult of the Birdman reflected a very visible expression of political competition and cooperation at the island-wide level. This paper synthesizes recent archaeological and chronological information for the cult’s central site – ‘Orongo, in order to document the temporal shift in ideology from an emphasis on lineage autonomy to a more integrated leadership. While Rapa Nui was experiencing internal pressures from the loss of arable land and territory reconfiguration, brought on by soil nutrient depletion and limited rainfall, we hypothesize it was only the events associated with repeated European contact that were sufficiently disruptive to initiate rapid social change at the collective level. One social response was a realignment of ideological values represented by the formation of the Cult of the Birdman. The first cult activities, in front of the stone houses at ‘Orongo, occurred during the early AD1600s. Activities intensified near AD1800 possibly due to the negative impacts of European contact and it is hypothesized that stone house construction occurred at this time.

Temporal coverage Collections include artefacts that may date from the initial settlement by the ancestors of Māori around AD 1280 through the period of regular contact with Europeans after AD 1850. (2) Methods Each artefact was assessed mid-z elements (Nb, Rb, Y, Zr, Sr) and other elements (Fe, Mg) using a pXRF and then matched to a geochemically distinct natural source of obsidian. Geographically ambiguous source assignments, such as assignment to a general volcanic zone, were not included. We note that out of the 15 known geochemically distinct natural sources of New Zealand obsidian [12], only 13 have been identified in archaeological collections. Steps The two university laboratories that produced this data each specified procedures in a series of publications. The specific lab protocols and machines used evolved over this period and so readers are directed to original studies for a fuller description. Examples of methods for Bruker pXRF, a type used in both laboratories, is summarised below.

The obsidian dating method converts the quantity of diffused molecular water within a near‐surface hydration layer to elapsed time using an experimentally derived diffusion coefficient predicted from the structural water content of the glass. Infrared spectroscopic transmission measurements on transparent archaeological samples record vibrational responses of water bands in the near‐infrared region, permitting determination of structural water content (OH), and the amount of diffused ambient water (H₂O). In this application, the H₂O water band at 5200 cm⁻¹ is measured directly. The accuracy of the approach is assessed by an evaluation of the precision of each contributing variable. The new protocol is evaluated using obsidian artifacts from radiocarbon‐dated deposits at Salamanca Cave in Argentina.