Isotopic Reconstructions of Prehistoric Diet from Burnt Bones

骨胶原蛋白的稳定的氮和碳同位素比率是关于古代人群饮食信息的极其重要的来源。 它们提供了对个体饮食的定量估计，因此为古代人类之间和内部的饮食差异提供了显着的见解。 然而，它们不能用于烧焦或燃烧的骨头，因为已知同位素比率在高于150 ℃的温度下加热时会发生变化。 这是一个严重的限制，因为许多文化，如欧洲青铜时代和古罗马，火葬他们的死者，只留下烧焦的骨头。 对于某些非常古老的遗址，例如早期人类遗址，古人类骨骼是唯一保存下来的骨骼类型，因此无法用现有技术使用。 煮熟的动物骨头，可以提供有关饮食的信息，目前也不能使用。 初步的实验室数据揭示了碳化骨的同位素比率的变化与来自通过碳化在胶原中产生的稳定自由基的电子自旋共振（ESR）谱的性质（g值）之间的关系。 在NSF的支持下，考古学家和化学家的跨学科团队将由人类学和化学本科生协助，进一步量化这种关系，并严格评估其对考古问题的适用性。 通过比较实验室标本和来自北美东部两个不寻常遗址的史前骨骼的同位素比和ESR g值，我们将评估是否有可能使用ESR谱重建燃烧骨骼的原始同位素比。 位于美国伊利诺伊山谷下游的Klunk和Yokem遗址已经从其同位素生态学众所周知的人群中产生了火化和未火化的墓葬。 在许多情况下，埋葬只是部分火化，留下烧焦和未烧焦的骨头，甚至经常显示出炭化梯度的骨头，因此有可能对单个骨头的烧焦和未烧焦部分进行采样。 这些遗址提供了一个机会，可以调查1,000年至6,000年前埋葬后成岩（化学）变化对燃烧骨骼的影响。 因此，我们将能够评估埋葬时间和条件对重建的影响。 如果ESR光谱可以用来重建未加热的同位素比率，它将开辟一个全新的领域，稳定同位素分析可以应用于重建史前饮食。 此外，对照样本将为需要重建火灾或爆炸受害者热历史的法医科学家提供有用的信息。 该项目将涉及八名本科生在一个跨学科的研究团队结合考古学和化学。

The stable nitrogen- and carbon-isotope ratios of bone collagen are extremely important sources of dietary information about ancient populations. They provide quantitative estimates of individual diets and have therefore provided remarkable insights into dietary variation both between and within ancient human populations. However, they cannot be applied to charred or burned bones because it is known that the isotopic ratios change upon heating at temperatures higher than 150oC. This is a serious limitation because many cultures, such as those of the European Bronze Age and ancient Rome, cremated their dead, leaving only burned bones. And for certain types of very old sites, such as early hominid ones, carbonized bones are the only type of bone preserved, and are thus not usable with current technologies. Cooked animal bones, which could provide information about diet, also cannot be used at present. Preliminary laboratory data reveal a relation between the change of isotopic ratios of charred bone and a property (the g-value) of the electron spin resonance (ESR) spectrum from stable free radicals that are produced in the collagen by charring. With NSF support, an interdisciplinary team of an archaeologist and a chemist will be assisted by anthropology and chemistry undergraduates to further quantify this relationship and critically evaluate its applicability to archaeological problems. By comparing the isotope ratios and ESR g-values of laboratory specimens and prehistoric bones from two unusual sites in eastern North America, we will assess the whether it is possible to use ESR spectra to reconstruct the original isotope ratios of burned bones. The Klunk and Yokem sites in the lower Illinois Valley, USA have produced cremated and uncremated burials from populations whose isotopic ecologies are well known. In many cases, the burials were only partially cremated, leaving burned and unburned bones, and frequently even bones that show a charring gradient, so that is possible to sample burned and unburned portions of a single bone. The sites provide an opportunity to investigate the effects of diagenetic (chemical) changes on burned bones after burial from periods between 1,000 and 6,000 years ago. We will thus be able to assess the effects of burial time and conditions on the reconstructions. If ESR spectra could be used to reconstruct unheated isotope ratios, it would open up entirely new areas where stable isotope analysis could be applied to the reconstruction of prehistoric diet. In addition, the control samples will provide information useful to forensic scientists who need to reconstruct the thermal histories of victims of fires or explosions. The project will involve eight undergraduate students in an inter-disciplinary research team combining archaeology and chemistry.