Early Prehistory and Quaternary Ecology, Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen 72070, Germany.
Applied Mineralogy, Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen 72074, Germany.
Proc Natl Acad Sci U S A. 2024 Mar 5;121(10):e2318560121. doi: 10.1073/pnas.2318560121. Epub 2024 Feb 26.
In the Stone Age, the collection of specific rocks was the first step in tool making. Very little is known about the choices made during tool-stone acquisition. Were choices governed by the knowledge of, and need for, specific properties of stones? Or were the collected raw materials a mere by-product of the way people moved through the landscape? We investigate these questions in the Middle Stone Age (MSA) of southern Africa, analyzing the mechanical properties of tool-stones used at the site Diepkloof Rock Shelter. To understand knapping quality, we measure flaking predictability and introduce a physical model that allows calculating the relative force necessary to produce flakes from different rocks. To evaluate their quality as finished tools, we investigate their resistance during repeated use activities (scraping or cutting) and their strength during projectile impacts. Our findings explain tool-stone selection in two emblematic periods of the MSA, the Still Bay and Howiesons Poort, as being the result of a deep understanding of these mechanical properties. In both cases, people chose those rocks, among many others, that allowed the most advantageous trade-off between anticipated properties of finished tools and the ease of acquiring rocks and producing tools. The implications are an understanding of African MSA toolmakers as engineers who carefully weighed their choices taking into account workability and the quality of the tools they made.
在石器时代，收集特定的岩石是制作工具的第一步。关于在石器采集过程中做出的选择，我们知之甚少。这些选择是基于对石头特定属性的了解和需求做出的吗？还是采集到的原材料仅仅是人们在景观中移动的副产品？我们在南部非洲的中石器时代（MSA）研究了这些问题，分析了迪普克洛夫石窟遗址使用的工具石器的机械性能。为了了解剥落质量，我们测量了剥落的可预测性，并引入了一种物理模型，该模型可以计算出从不同岩石中产生剥落所需的相对力。为了评估它们作为成品工具的质量，我们研究了它们在重复使用活动（刮削或切割）中的阻力以及在投射物撞击下的强度。我们的发现解释了 MSA 中两个典型时期（斯泰尔湾和豪伊森斯波特）的石器选择，是对这些机械性能的深刻理解的结果。在这两种情况下，人们选择了那些石头，而不是其他许多石头，因为这些石头在预期成品工具的属性和获取岩石以及制作工具的便利性之间实现了最有利的权衡。这意味着我们可以理解非洲 MSA 的石器制造者是工程师，他们在考虑到可加工性和工具质量的情况下，仔细权衡了他们的选择。
