Collaborative Research: Rodent Diets and Habitat Reconstructions in South Africa: an Actualistic and Applied Multidisciplinary Study

在美国国家科学基金会的支持下，Sponheimer、Ungar和Passey以及一个由同事组成的国际团队将调查人类进化的环境背景。该团队包括来自美国、加拿大、以色列和南非的研究人员，他们将利用他们在脊椎动物古生物学、同位素地球化学、野生动物生态学和人类古生物学方面的专业知识，通过啮齿动物饮食生态学的视角来研究人类古生态学。人们早就认识到，啮齿动物的生态多样性和较小的活动范围使它们成为重建过去环境的特别有用的工具。然而，对啮齿动物的研究传统上是对化石标本的生态学进行假设，而不是直接测量饮食特征。相比之下，该项目将直接确定啮齿动物的饮食，以调查现代啮齿动物饮食生态与栖息地之间的关系，然后将这些知识应用于南非人类化石记录。采用牙齿微磨损织构分析、稳定碳同位素分析和锶同位素分析对饮食进行研究。前两种方法提供了饮食属性的直接测量（例如，食物的机械特性，树木的水果/叶子与草的机械特性），而最后一种方法可以确定动物在景观中的生活位置，从而可能导致更精细的空间环境重建。该项目将分为三个阶段。在第一阶段，研究小组将对现代啮齿动物饮食与栖息地特征之间的关系进行广泛的研究。在第二阶段，研究小组将确定猫头鹰栖息地的现代啮齿动物的饮食在多大程度上反映了当地的栖息地，本质上是调查猫头鹰捕食对环境信号的影响程度。最后一个阶段将需要将这些知识应用于南非斯特克方丹山谷及其周围的化石遗址，这些遗址的历史从250万年到70万年不等。这个项目的智力价值在于，它将提供早期人类生态和环境的新证据，这样做将有助于解决有关人类适应和进化的问题。例如，人类假定的祖先，脑容量较大的早期人属，是在首选环境显著恶化后才出现在非洲的吗？这种环境变化是否导致了我们脑容量较小、适应性较差的进化“表亲”傍人的灭绝？这也为利用啮齿动物饮食生态学重建古环境奠定了坚实的基础，对其他考古和古生物遗址具有广泛的实用价值。此外，这将标志着首次使用多种技术来调查动物饮食、丰度和环境/气候参数在长（200万年）时间尺度上的交集。此外，作为该项目一部分的分析发展将用于考古学以外的领域，包括生物人类学、地质学、地球化学、保护生态学和古生物学。本研究的更广泛影响是，它将促进国际合作，为来自代表性不足群体的学生提供培训，丰富本科教学和研究生指导，并作为更好地公众理解科学和技术的平台。这对阿肯色大学来说尤其重要，这是一所资金不足的EPSCoR州的公立大学。

With National Science Foundation support, Drs. Sponheimer, Ungar, and Passey and an international team of colleagues will investigate the environmental context of human evolution. The team includes researchers from the U.S., Canada, Israel,and South Africa who will use their expertise in vertebrate paleontology, isotopic geochemistry, wildlife ecology, and human paleobiology to study human paleoecology through the lens of rodent dietary ecology. It has long been recognized that the ecological diversity and small home ranges of rodents make them particularly useful tools for reconstructing past environments. However, studies of rodent faunas have traditionally made assumptions about the ecology of fossil specimens rather than measuring dietary attributes directly. In contrast, this project will directly determine rodent diets to investigate the relationship between modern rodent dietary ecology and habitats, and then apply this knowledge to the South African human fossil record. Diet will be studied using dental microwear texture analysis, stable carbon isotope analysis, and strontium isotope analysis. The first two provide direct measures of dietary attributes (e.g., mechanical properties of foodstuffs, tree fruits/leaves versus grasses), while the last allows determination of where animals lived on the landscape, potentially resulting in more spatially-refined environmental reconstructions. The project will have three phases. In the first phase, the research team will conduct an extensive study of the relationship between modern rodent diets and habitat features. In the second phase, the team will determine the degree to which the diets of modern rodents from owl roosts reflect local habitats, essentially investigating the degree to which owl predation biases the environmental signal. The last phase will entail application of this knowledge to fossil sites in and around the Sterkfontein Valley, South Africa that are from ~2.5 million to ~700 thousand years old. The intellectual merit of this project is that it will provide new evidence of early hominin ecology and environments, and in so doing, will help address questions about hominin adaptations and evolution. For instance, did humans putative ancestors, big-brained early Homo, emerge in Africa only after significant deterioration of preferred enviroments, and did such environmental change contribute to the extinction of our smaller-brained, and presumably less adaptable, evolutionary "cousin" Paranthropus? It will also establish a firmer basis for using rodent dietary ecology to reconstruct paleoenvironments, which will be of broad utility at other archaeological and paleontological sites. In addition, it will mark the first time that multiple techniques have been used to investigate the intersection of animal diets, abundances, and environmental/climatic parameters over long (2 million year) timescales. Furthermore, the analytical developments to be made as part of this project will be of use for fields beyond archaeology including biological anthropology, geology, geochemistry, conservation ecology and paleontology. The broader impacts of this study are that it will foster international collaboration, provide training for students from underrepresented groups, enrich undergraduate teaching and graduate mentoring, and be used as a platform for bettering public understanding of science and technology. This is especially relevant for the University of Arkansas, a public university in an underfunded EPSCoR State.