Isotopic Methods for Sourcing Shell Beads in California

在国家科学基金会的支持下，杰尔默·埃肯斯博士和霍华德·斯佩罗博士将在之前研究的基础上，开发一种可靠的方法来追踪加州中部古代贝壳珠子的地理来源。这种方法是基于保存在用于制造珠子的贝壳中的稳定同位素特征。加利福尼亚州海岸的季节性水温、盐度以及寒冷和营养丰富的海水的上升流都有很大的变化。总而言之，这些效应赋予了沿海岸不同部分生长的贝壳独特的同位素特征。当贝壳在海岸上被收集起来，变成珠子，并在内陆交易时，它保留了贝壳的碳酸钙结构中最初生长的地方的特征。当考古学家找回远离海岸的贝壳文物时，他们可以从文物并通过同位素签名向后工作，以确定贝壳最初在哪里生长。考古学家使用这些类型的技术来追踪原材料在整个景观中的移动，这使他们能够重建古代的贸易和互动网络。通过这些贸易网络，可以评估人们如何适应不断变化的社会和自然环境。随着新技术的创新和推广，对支持这些技术的原材料的需求也在增加，可靠地获得当地无法获得的原材料将是重要的。考古学家可以通过检查原材料从哪里获得，生产的文物的风格，以及这两种技术是如何随着时间的推移共同进化的，来追溯不同技术的历史和发展。虽然这里要研究的具体案例研究涉及加州中部的古代贝壳文物贸易和交换，但这种方法几乎可以应用于世界任何地方的贝壳文物。在加利福尼亚州，土著人民通常用紫色橄榄壳Olivla biplicata制作珠子。在接触的时候，也就是18世纪末，这些贝珠的使用方式类似于货币，它们在考古遗址中随处可见。目前还没有确切的统计数字，但在过去的100年里，考古学家已经从加州中部的遗址中发现了100多万颗奥利维拉珠子。即使是加利福尼亚州最早的遗址，可以追溯到10000多年前，也有由双褶纹斑潜蝇制成的珠子。加州原住民为什么选择这种特殊的物种尚不清楚，但这项拟议的研究可能能够解决这个问题。该项目将支持一名兼职博士后研究员和一到两名加州大学戴维斯分校的本科生，他们将接受地球化学和考古分析方面的培训。这些数据和分析结果将通过加州大学戴维斯分校的外联活动与加州中部社区共享，包括在加州大学人类学博物馆的公开展示，博德加湾海洋实验室的学童项目，以及在专业会议上的演讲。

With support from the National Science Foundation, Drs. Jelmer Eerkens and Howard Spero will build on previous research to develop a robust method for tracing the geographic origin of ancient shell beads in Central California. The approach is based on stable isotope signatures preserved in the shells used to make beads. There is significant variation along the California Coast in seasonal water temperature, salinity, and upwelling of cold and nutrient-rich seawater. Together, these effects impart distinctive isotopic signatures to shells growing along different sections of the coast. When a shell is collected on the coast, turned into a bead, and traded inland, it retains the signature of where it originally grew in the calcium carbonate structure of its shell. When archaeologists recover shell artifacts far away from the coast, they can work backwards, from the artifact and through the isotopic signature, to determine where the shell originally grew.Archaeologists use these types of techniques to trace the movement of raw materials across the landscape and this allows them to reconstruct ancient trading and interaction networks. These trading networks, by extension, allow evaluation of how people adapted to their ever-changing social and natural environments. As new technologies were innovated and spread, demand for raw materials to support them also increased, and reliable access to raw materials that were not locally available would have been important. Archaeologists can trace the history and development of different technologies by examining where raw materials were procured, the style of artifacts produced, and how the two co-evolved over time. Although the specific case study to be examined here addresses ancient trade and exchange of marine shell artifacts in Central California, the approach can be applied to shell artifacts almost anywhere in the world.In California, indigenous peoples commonly made beads out of the purple olive shell, Olivella biplicata. At the time of contact, in the late 1700s, these shell beads were used in a manner akin to currency and they are ubiquitous in archaeological sites. An exact tally is not available, but over the last 100 years archaeologists have recovered well over a million Olivella beads from sites in Central California. Even the earliest sites in California, dating to over 10,000 years ago, have beads made out of Olivella biplicata. Why Native Californians selected this particular species is not known, but is something the proposed research may be able to address.This project will support one part-time post-doctoral researcher and one to two UC Davis undergraduate students, who will be trained in geochemical and archaeometric analysis. The data and resulting analysis will be shared with the Central California community through outreach efforts at UC Davis, including public displays at the UCD Anthropology Museum, programs with school children at Bodega Bay Marine Laboratory, and presentations at professional conferences.