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

在NSF的支持下，Ann Russell博士、Robert Bettinger博士和Michael Kennedy先生将使用从14C年代考古组件中收集的加州海贻贝(Mytilus Calfornianus)贝壳边缘的稳定氧和碳同位素(d18O和d13C)来确定过去8600年史前加州北部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根据d18O和d13C的年度记录重建的海洋条件变化之间的关系。近年来，人们越来越多地关注狩猎-采集海洋适应的出现，以及气候变化作为一种有选择的力量在塑造文化反应方面的作用。加利福尼亚州南部和中部的重大文化变化，如使用边际资源以及日益增加的经济和社会政治复杂性，可能是由于与海洋表面温度(SST)和海洋生产力变化有关的资源压力造成的。关于加州北部海岸狩猎-采集进化的这些方面，人们知之甚少。重建加州北部海岸的季节性觅食模式，以及上升流强度和海洋营养水平，将为理解该地区海洋资源集约化的出现提供关键信息。先前的研究表明，软体动物贝壳方解石中的稳定同位素(d18O和d13C)记录提供了有关海洋环境条件(SST、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，并表明同时使用加州贻贝终端边缘(生长边)的d18O和d13C的方法是确定收获季节的有价值的工具。狩猎-采集者如何密集地利用加州北部全年的边缘海洋资源(贝类)，以及海洋气候在强化海洋觅食策略的制定中扮演了什么角色？为了解决这些问题，研究小组将在加利福尼亚州博德加湾附近的五个14C年代考古成分中产生贻贝壳方解石中d18O和d13C的三个季节性记录。这些剖面图将提供关于平均海洋环境状况的信息，以及在占领时SST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件至少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。这项研究的一个重要方面将是继续对壳牌终端边缘耦合的d18O和d13C的使用进行现代校准/核查，以确定收获季节。利用这些研究的结果和其他考古数据，研究小组将重建自公元前8600年以来加州北部海洋狩猎-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年来的年度觅食强度进行区域评估，并将提供比先前研究提供的对加州北部海岸海洋资源集约化的更复杂的检查。

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.