Isotopic Evidence of Sources for Central California Olivella Beads

ABSTRACT

Without the large bead production sites present on the Channel Islands, the origin of Olivella beads in central California has been largely speculative. Stable isotope analysis of shell carbonate provides a useful test of source, production, and distribution hypotheses by providing information about the environment of shell formation. We reassess results of previous stable isotope sourcing studies and employ a cluster analysis that suggests most Olivella beads recovered from central California were produced from shell harvested from the Central Coast or Bay Area, but conveyance from southern California also contributed to the bead supply by the end of Phase 1 of the Middle Period (ca. 1,545 BP). Bead production in central California appears decentralized relative to large Channel Island workshops, a difference that likely reinforced the divergent sociopolitical trajectories of the regions.

RESUMEN

Sin los grandes sitios de producción de las cuentas en las Islas de Canal, el origen de las cuentas Olivellas en el centro de California ha sido principalmente especulativo. El análisis de isótopos estables de carbonato de conchas marinas produce una prueba de las hipótesis de origen, producción, y distribución al proveer información sobre el entorno de formación de la valva. Reevaluamos estudios de fuentes de isótopos estables y usamos un análisis de conglomerados que sugiere que la mayoría de las valvas Olivella recuperadas en el centro de California se produjeron a partir de cuentas recolectadas en la costa central o en el área bahía. El comercio desde el sur de California también contribuyó al suministro de valvas al final de la Fase 1 del Período Medio (ca. 1,545 AP). Producción de cuentas en el centro de California parece descentralizada en relación con talleres de las Islas de Canal, una diferencia que probablemente reforzada por las trayectorias sociopolíticas divergentes de las regiones.

KEYWORDS:

• Shell beads
• stable isotopes
• bead production
• trade and exchange
• sociopolitical complexity
• Channel Islands
• central California
• cluster analysis

Acknowledgements

We thank Nathan Stevens, Jessica Bean, and Rowan Gard for help in preparing samples for analysis. Assistance with abstract translation was provided by Laura Steele, Dr. Pablo Andres Cahiza, and Ishmael Medina.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Notes

1 Although many recent archaeological publications use the genus Callianax, the taxonomic classification of the genus is controversial, with morphological phylogeny elevating the subgenus Callianax (Adams and Adams 1853) to full genus status (Powell, Vervaet, and Berschauer 2020) while genetic phylogeny retains Olivella (Swainson 1831) pending further study (Kantor et al. 2017). With acknowledged participation as a pawn in heated phylogenetic battles, we here retain the use of Olivella for both artifact type and genus for consistency with archaeological literature and out of parsimony until the matter is resolved.

2 The analysis of beads to be sourced in this study is primarily limited to wall beads – beads manufactured from a portion of the outer shell wall, as opposed to beads manufactured by modification of the whole shell (e.g., spire-removed beads) or from the callus or columella. Wall beads represent a finished product with relatively high manufacture input (as opposed to spire-removed beads), and incorporate the growth bands required for serial sampling (unlike callus and columella). However, end-ground beads (types B1 and B2), made by more intensive modification of the whole shell, are included. Lipped beads (Class E) are also included, even though they incorporate a portion of the callus, but only the wall section of the bead was sampled.

Additional information

Funding

This work was supported by Wenner-Gren Foundation to JWE and JSR and from the National Science Foundation to JWE and HJS [#BCS-1220048 and #BCS-0504615].