Testing Stable Isotopes of Human Dental Calculus as a Nondestructive Proxy for Paleodiet

测试人类牙结石的稳定同位素作为古饮食的无损替代物

• 批准号: 1335302
• 负责人: George Scott
• 金额: $ 11.95万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1335302&HistoricalAwards=false
• 关键词: Testing; Stable; Isotopes; Human; Dental

For over thirty years, bioarchaeologists have used stable carbon and nitrogen isotopes to evaluate the dietary habits of earlier human populations. Given that bone preserves better than skin, fingernails, and hair in most taphonomic contexts, the primary biomaterial used in isotope analysis is collagen. This protein, the organic fraction of calcified bone, is not directly available for analysis so methods used to isolate collagen are destructive. In contrast to collagen, dental plaque is a biofilm that forms on the teeth of humans and other animals. When plaque accumulates and is not removed, it calcifies to form dental calculus. In 2008, calculus was collected from medieval and post-medieval Basque skeletons from Vitoria, Spain with the aim of isolating plant phytoliths. The goal of this project was to determine if researchers could observe directly the introduction of edible plants from the New World to Spain, with special emphasis on maize. Unfortunately, processing calculus samples to find phytoliths was minimally successful. With 58 samples and diminished hopes of finding phytoliths, five calculus samples were sent to the geochemistry lab at the University of Nevada, Reno for stable isotope analysis. The researchers could find no evidence in the literature that anyone had ever attempted to obtain stable isotope signatures from calculus, so they were not optimistic there would be enough carbon and nitrogen to get a good signal from a biomaterial primarily made up of calcium and phosphate minerals. The initial analysis of five samples yielded surprising results. There was more carbon than anticipated, it yielded ratios that could be replicated on repeated trials, and these ratios were close to the values obtained from bone collagen for earlier European populations. When the samples were tested for nitrogen, a similar result was found. There is sufficient nitrogen in calculus to get a good isotope estimate and the results were consistent with values for earlier European populations based on bone collagen. This project does not center on the utility of stable carbon and nitrogen isotopes in paleodietary analysis as that has been demonstrated in hundreds of studies over the past 35 years. The project goal is to determine whether a new biomaterial ? dental calculus ? can be used to estimate C and N ratios, especially in instances where destructive analysis is prohibited. The key is that calculus is not part of the skeletal or dental system but is an add-on that goes through a cycle of addition and removal (by a dental hygienist) in modern human populations. Prior to dental hygiene, emphasis was more on addition and less on removal so calculus is common on the teeth of earlier humans. While results to date are encouraging, this project will conduct the necessary additional tests to determine if dental calculus can be a consistent and effective proxy for isotope analysis. Calculus samples will be obtained from human groups with divergent subsistence patterns, including Greenlandic Inuit, Greenlandic Norse, classic and colonial Maya, and prehistoric Peruvians, to determine if isotopes from calculus exhibit differences in protein consumption and the varied use of C3 and C4 plants. If consistent results can be obtained, dental calculus might provide a much more accessible source of data and may also avoid resistance by Native American groups to this sort of analysis using destructive analyses techniques on human skeletal remains. The project will validate a method of isotopic analysis that is faster, non-destructive and less expensive than the current standard testing bone collagen, which would be a major contribution to the sub-field of paleo-diet studies.

三十多年来，生物考古学家一直使用稳定的碳和氮同位素来评估早期人类的饮食习惯。 鉴于在大多数埋藏学背景下，骨比皮肤、指甲和毛发保存得更好，同位素分析中使用的主要生物材料是胶原蛋白。 这种蛋白质是钙化骨的有机部分，不能直接用于分析，因此用于分离胶原蛋白的方法是破坏性的。 与胶原蛋白相反，牙菌斑是在人类和其他动物的牙齿上形成的生物膜。当牙菌斑积聚而不被清除时，它会钙化形成牙结石。2008年，从西班牙维托里亚的中世纪和后中世纪巴斯克骨骼中收集了牙石，目的是分离植物植硅体。 该项目的目标是确定研究人员是否可以直接观察从新大陆引进到西班牙的食用植物，特别是玉米。不幸的是，处理结石样本以找到植硅体的成功率很低。 在58个样本和寻找植硅石的希望渺茫的情况下，5个结石样本被送往内华达州里诺大学的地球化学实验室进行稳定同位素分析。 研究人员在文献中找不到任何证据表明有人曾试图从微积分中获得稳定的同位素特征，因此他们并不乐观，因为有足够的碳和氮可以从主要由钙和磷酸盐矿物组成的生物材料中获得良好的信号。 对五个样本的初步分析得出了令人惊讶的结果。 碳含量比预期的要多，它产生的比率可以在重复试验中重复，这些比率接近于从早期欧洲人群的骨胶原中获得的值。当对样本进行氮检测时，发现了类似的结果。结石中有足够的氮，可以得到良好的同位素估计，结果与基于骨胶原的早期欧洲人群的值一致。 这个项目并不像过去35年里数百项研究所证明的那样，把稳定的碳和氮同位素用于古食物分析。 该项目的目标是确定是否一种新的生物材料？牙垢？可用于估算C和N比率，特别是在禁止破坏性分析的情况下。关键是，牙石不是骨骼或牙齿系统的一部分，而是一种附加物，在现代人群中经历了一个添加和去除（由牙科医生）的循环。 在牙齿卫生之前，人们更多地强调增加而不是去除，因此牙石在早期人类的牙齿上很常见。 虽然迄今为止的结果令人鼓舞，但该项目将进行必要的额外测试，以确定牙结石是否可以作为同位素分析的一致和有效的替代品。 结石样本将从不同生存模式的人类群体中获得，包括格陵兰因纽特人，格陵兰挪威人，古典和殖民玛雅人以及史前秘鲁人，以确定结石的同位素是否表现出蛋白质消耗的差异以及C3和C4植物的不同用途。 如果能够获得一致的结果，牙垢可能会提供一个更容易获得的数据来源，也可能避免美洲原住民群体对这种使用人类骨骼遗骸破坏性分析技术的分析的抵制。 该项目将验证一种同位素分析方法，这种方法比目前测试骨胶原的标准方法更快、非破坏性和更便宜，这将是对古饮食研究子领域的重大贡献。