Doctoral Dissertation Improvement :Influences of Materials Properties and Biomechanics on Stone Tool Production

与他们的大猿亲戚相比，人类已经从他们最初的家园在非洲的一个有限的地区蔓延到占据甚至统治几乎所有的陆地栖息地。他们的成功部分归功于使用和依赖技术，其中石器是最早的证据。石器的形式，连同它们的使用和制造（敲击）的数据，也提供了人类认知发展的长期记录。由于工具生产的早期对应于手、手腕和手臂形态的重大变化，研究人员认为，石器的使用增加在塑造现代人类上肢解剖结构方面发挥了作用。 然而，人们对用不同原材料生产石器所涉及的断裂力学和石器生产过程中上肢的生物力学还没有很好的了解。断裂力学和上肢形态对所产生的石器的相互作用关系也不清楚。本项目从跨学科的角度解决这些问题，将岩石分析与断裂力学和生物力学实验相结合。将测试两个主要假设：1。生产特定薄片形态所需的破碎力的大小和方向可从原材料性质预测（即，韧性）和芯形状，以及，2.）人类进化的上肢形态在高效的石器生产中起着关键作用。 研究设计包括对相关原材料进行断裂力学实验，然后使用数字运动分析系统对knapping运动进行两阶段分析，以研究上肢运动模式和作用于手和手腕的力。运动分析研究将涉及10名经验丰富的knapper复制石片和工具在两种不同的原材料从四个不同的连续工具传统（Oldowan，Acheulian，Levallois和中石器时代）。这两个阶段将涉及相同的任务，但在第二阶段，knappers的手腕将被限制在约30°的前后运动，以模拟非洲猿和早期人类的原始条件。将比较和分析两个阶段的薄片和工具在自然与约束条件下运动的准确性和效率。本研究的目的是确定如何在石器生产（材料韧性，断裂行为，核心形状和上肢运动学）的基本变量相互作用，以确定薄片形态，knapping精度和能量效率。这项研究将为石器生产的出现和发展以及人类上肢的进化提供新的见解。 这反过来又具有重要的临床意义，了解上肢关节运动，形态的变化，损伤和退行性骨疾病的影响。

In contrast to their great ape relatives, humans have spread from their original home in a limited region of Africa to occupy and even dominate almost all terrestrial habitats. Their success has in part been attributed to the use of, and dependence on, technology of which stone tools represent the earliest evidence. The form of stone tools, together with data on their use and manufacture (knapping), also provide a long record of human cognitive development. Since the early period of tool production corresponds to major changes in the morphology of the hand, wrist and arm, researchers have suggested that increasing use of stone tools played a role in shaping modern human upper limb anatomy. The fracture mechanics involved in producing stone tools in different raw materials and the biomechanics of the upper limb during stone tool production, however, are not well understood. The interactive relationship of fracture mechanics and upper limb morphology on the resulting stone tool is also unclear. This project addresses these issues from an interdisciplinary perspective that integrates lithic analysis with experiments in fracture mechanics and biomechanics. Two main hypotheses will be tested: 1.) magnitude and direction of knapping forces required to produce specific flake morphologies can be predicted from raw material properties (i.e., toughness) and core shape, and, 2.) evolved upper limb morphology in Homo plays a key role in efficient stone tool production. The research design involves fracture mechanics experiments on relevant raw materials, followed by a two phase analysis of knapping motions using a digital motion analysis system to study upper limb motion patterns and forces acting across the hand and wrist. The motion analysis study will involve ten experienced knappers replicating stone flakes and tools in two different raw materials from four different successive tool traditions (Oldowan, Acheulian, Levallois and Middle Stone Age). The two phases will involve the same tasks but in the second phase the knappers' wrists will be restrained to ~30° of anterior-posterior motion to simulate the primitive condition found in African apes and early hominins. Flakes and tools from the two phases will be compared and analyzed for the accuracy and efficiency of motions during the natural vs. the restrained condition. The goal of this study is to determine how fundamental variables involved in stone tool production (material toughness, fracture behavior, core shape and upper limb kinematics) interact to determine flake morphology, knapping accuracy, and energetic efficiency. The study will provide new insights into the advent and development of stone tool production and the evolution of the human upper limb. This in turn has significant clinical implications for understanding upper limb joint motions, variations in morphology, and the impact of injuries and degenerative bone diseases.