Stable isotopes as a tool for investigating changes in Holocene hunter-gatherer strategies along the northern California coast

在美国国家科学基金会的支持下，安·罗素博士、罗伯特·贝廷格博士和迈克尔·肯尼迪先生将在加利福尼亚贻贝（Mytilus californianus）贝壳的边缘使用稳定的氧和碳同位素（d18O和d13C），这些贝壳从14c年代的考古部件中收集，以确定在过去8600年里，史前北加州狩猎采集者收获这种边缘海洋资源的季节。此外，他们将评估贻贝收获的季节性与d18O和d13C年记录重建的海洋条件变化之间的关系。近年来，人们越来越关注狩猎采集者海洋适应性的出现，以及气候变化在形成文化反应中的选择性力量所起的作用。加州南部和中部的主要文化变化，如边际资源的使用以及经济和社会政治复杂性的增加，可能是由与海洋表面温度（SST）和海洋生产力变化相关的资源压力发展而来的。人们对加利福尼亚北部沿海地区狩猎采集者进化的这些方面知之甚少。重建北加州海岸的季节性觅食模式，以及上升流强度和海洋营养水平，将为了解该地区海洋资源集约化的出现提供关键信息。以往的研究表明，软体动物壳方解石中稳定同位素（d18O和d13C）的记录提供了海洋环境条件（海温、营养水平和推断的海洋生产力）的重要信息。初步结果证实了这一点，并建议同时使用加州贻贝（Mytilus californianus，加利福尼亚贻贝）的终缘（生长边缘）的d18O和d13C的方法是确定收获季节的有价值的工具。在加利福尼亚北部，狩猎采集者全年对边缘海洋资源（贝类）的利用有多密集？海洋气候在强化海洋觅食策略的发展中发挥了什么作用？为了解决这些问题，研究小组将从加利福尼亚博德加湾附近的五个14c考古成分中提取贻贝方解石中d18O和d13C的三个季节记录。这些剖面将提供平均海洋环境条件的资料，以及占领时期海温和d13C的典型季节变化范围。除了这些长期记录外，研究人员还将从每个组成部分的至少20个额外贝壳的末端边缘获得同位素数据，以确定收获季节。研究的一个重要方面将是继续进行现代校准/验证，从壳终端边缘使用耦合的d18O和d13C，以确定收获季节。利用这些研究结果与其他考古数据相结合，研究小组将重建自8600年前以来加利福尼亚北部海洋狩猎采集者的环境条件和适应策略的变化。这项研究将允许对过去~8600年的年度觅食强度进行区域评估，并将对加利福尼亚北部海岸的海洋资源集约化提供比以前研究更复杂的检查。

With NSF support, Dr. Ann Russell, Dr. Robert Bettinger, and Mr. Michael Kennedy will use stable oxygen and carbon isotopes (d18O and d13C) at the edges of California sea mussel (Mytilus californianus) shells collected from 14C-dated archaeological components to determine the season in which prehistoric northern California hunter-gatherers harvested this marginal marine resource over the last 8600 years. In addition, they will evaluate the relationship between seasonality of the mussel harvest and changes in marine conditions reconstructed from annual records of d18O and d13C. In recent years, there has been increased focus on the emergence of hunter-gatherer maritime adaptations and the role of climate change as a selective force in shaping cultural responses. Major cultural changes in southern and central California, such as the use of marginal resources as well as increasing economic and sociopolitical complexity, may have developed from resource stress related to changes in sea-surface temperature (SST) and marine productivity. Little is known about these aspects of hunter-gatherer evolution along the coast of northern California. Reconstruction of seasonal foraging patterns, as well as upwelling intensity and marine nutrient levels along the coast of northern California will provide critical information for understanding the emergence of marine resource intensification in this region.Previous research has shown that the record of stable isotopes (d18O and d13C) in shell calcite of mollusk shells provides important information on marine environmental conditions (SST, nutrient levels, and inferred marine productivity). Preliminary results confirm this and suggest that the approach of using both d18O and d13C of the terminal margin (growing edge) of Mytilus californianus (California sea mussel) shells is a valuable tool for determining the season of harvest.How intensively did hunter-gatherers utilize marginal marine resources (shellfish) throughout the year in northern California, and what role did marine climate play in the development of intensified marine foraging strategies? To address these questions, the research team will generate three seasonal records of d18O and d13C in mussel shell calcite from five 14C-dated archaeological components near Bodega Bay, California. These profiles will provide information on average marine environmental conditions, as well as the typical range of seasonal variation of SST and d13C at the time of occupation. In addition to these long-term records, the researchers will obtain isotopic data from the terminal margins of at least 20 additional shells per component to determine the season of harvest. An important aspect of the research will be to continue a modern calibration/verification of the use of coupled d18O and d13C from shell terminal margins to establish the season of harvest. Using the results of these studies in conjunction with other archaeological data, the research team will reconstruct changes in environmental conditions and in the adaptive strategies of maritime hunter-gatherers of northern California since 8600 BP. This research will permit a regional evaluation of annual foraging intensity over the last ~8600 years, and will provide a far more sophisticated examination of marine resource intensification along the northern California coast than previous research has offered.