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

与他们的类人猿亲戚不同，人类已经从他们最初在非洲有限区域的家园扩展到占据甚至主导几乎所有的陆地栖息地。他们的成功部分归因于对技术的使用和依赖，而石器是最早的证据。石器的形式，以及有关其使用和制造(指节)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阶段与手、腕和手臂的形态发生重大变化相对应，研究人员认为，越来越多地使用石器在塑造现代人类上肢解剖结构中发挥了作用。然而，不同原材料生产石器所涉及的断裂力学以及石器生产过程中上肢的生物力学还不是很清楚。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。这个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的实验相结合。将检验两个主要假设：1.)产生特定片状形貌所需的切削力的大小和方向可以根据原材料特性(即韧性)和芯子形状来预测，以及。人类上肢形态的进化对石器的高效生产起着关键作用。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打结运动进行两个阶段的分析，以研究上肢运动模式和手和手腕上的作用力。这项运动分析研究将涉及10名经验丰富的砍刀手，他们用两种不同的原材料复制石片和工具，这些材料来自四个不同的连续工具传统(Oldowan、Acheulian、Lvallois和中世纪石器时代)。这两个阶段将涉及相同的任务，但在第二阶段，截肢者的手腕将被限制为大约30°的前后运动，以模拟非洲猿类和早期人类的原始状态。对这两个阶段的薄片和工具在自然和约束条件下的运动精度和效率进行了比较和分析。这项研究的目的是确定石材工具生产中的基本变量(材料韧性、断裂行为、芯子形状和上肢运动学)如何相互作用来确定片层形态、切割精度和能量效率。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。这反过来又对了解上肢关节运动、形态变化以及损伤和退行性骨病的影响具有重要的临床意义。

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.