Large-Scale Excavations at the Ysterfontein 1 Middle Stone Age Rockshelter, Western Cape Province, South Africa

在美国国家科学基金会（National Science Foundation）的支持下，理查德·克莱因（Richard Klein）和一个多学科的美国/南非团队将在位于南非开普敦以北约70公里处的Ysterfontein 1号岩洞进行为期两个季节的挖掘。这次发掘的目的是阐明大约5万年前现代人从非洲向外扩张，并取代尼安德特人和其他非现代欧亚人的行为变化。关于非洲的行为是在5万年前突然发生变化，还是在25万至5万年前的漫长时间里逐渐发生变化，专家们意见不一。25万至5万年前的相关非洲遗址被划分为中石器时代（MSA），大多数遗址缺乏标准化的骨制品、艺术品或珠宝，以及其他考古物品，这些物品在历史上的狩猎采集者中广泛存在，直到5万年前才变得普遍。因此，大多数MSA站点都支持突变的观点。然而，也有一些地方，如刚果民主共和国的卡坦达群和南非的布隆博斯洞穴，已经发现了先进行为的标志，这些地点支持渐进或零碎的假设。Ysterfontein 1遗址中有一些人工制品和动物遗骸，可以用来测试其他选择，以及基于少数其他遗址的想法，即MSA人的狩猎和采集效率不如他们的继任者。Ysterfontein 1特别值得注意的是大量人类收集的潮间带贝壳，这可以用来追踪MSA的种群密度，因为平均贝壳大小可能反映了人类收集者的数量。总的来说，Ysterfontein 1的壳往往非常大，这意味着MSA的种群很小，但新的挖掘旨在逐层建立贝类的大小，以确定平均大小是否随着时间的推移而逐渐下降。该项目将使用最先进的技术来精确测定沉积物的年代，但已经很清楚的是，它们跨越了数千年或数万年，大约在10万到5万年前。因此，贝类大小的逐渐下降意味着MSA种群随着时间的推移而增长，这将支持MSA行为变化的零碎或渐进模型。这甚至可能意味着人口增长是5万年前现代人类从非洲向外扩张的基础。相比之下，贝类的大小随着时间的推移而下降的失败意味着MSA种群一直很小，这将支持MSA接近结束时突然行为变化的观点。对这种突变最合理的解释是，一种偶然的基因突变促进了现代人类大脑的发展。该项目主要是为了了解现代人类的行为起源，但它也将用于培训美国和南非的学生，用最先进的方法从一个分层很深的岩石掩体中恢复大型、无偏差、地层学控制的人工制品和动物样本。未来几代考古学家需要扩大精心挖掘的遗址样本，这不仅对解决现代人类起源的不确定性至关重要，而且对阐明人类进化中的许多其他突出问题也至关重要。

With National Science Foundation support, Richard Klein and a multidisciplinary American/South African team will excavate for two seasons at the Ysterfontein 1 rockshelter, about 70 km north of Cape Town, South Africa. The excavation is designed to illuminate the behavioral changes that allowed modern humans to expand from Africa about 50,000 years ago and to swamp or replace the Neanderthals and other non-modern Eurasians.Specialists disagree sharply about whether behavior changed abruptly in Africa just before 50,000 years ago or more gradually over a long interval between 250,000 and 50,000 years ago. The relevant African sites between 250,000 and 50,000 years ago are assigned to the Middle Stone Age (MSA), and the large majority lack standardized bone artifacts, art or jewelry, and other archaeological items that were widespread among historic hunter-gatherers and that became commonplace only after 50,000 years ago. Most MSA sites thus support the idea of abrupt change. However, there are a few, such as the Katanda cluster in the Democratic Republic of the Congo and Blombos Cave in South Africa, where markers of advanced behavior have been reported, and these sites support the gradual or piecemeal hypothesis. Ysterfontein 1 contains artifacts and animal remains that can be used to test the alternatives, together with the idea based on a small number of other sites, that MSA people hunted and gathered less effectively than their successors. Ysterfontein 1 is particularly notable for large numbers of humanly collected intertidal shells, which can be used to track MSA population density, since average shell size probably reflects the number of human collectors. In aggregate, the Ysterfontein 1 shells tend to be very large, implying small MSA populations, but the new excavation aims to establish shellfish size layer by layer to determine if average size declines progressively through time. The project will use state-of-the-art technology to date the deposits precisely, but it is already clear that they span thousands or tens of thousands of years sometime between 100,000 and 50,000 years ago. Thus, a progressive decline in shellfish size would imply that MSA populations were growing through time, and it would support the piecemeal or gradual model of MSA behavioral change. It could even mean that population growth underlay the modern human expansion from Africa 50,000 years ago. In contrast, the failure of shellfish size to decline through time would imply consistently small MSA populations, and it would support the idea of abrupt behavioral change near the end of the MSA. The most plausible explanation for such abrupt change would be a serendipitous genetic mutation that promoted the modern human brain.The project is intended primarily to inform on the behavioral origins of modern humans, but it will also serve to train American and South African students in state-of-the-art methods for recovering large, unbiased, stratigraphically controlled artifact and faunal samples from a deeply stratified rockshelter. The need for future generations of archaeologists to expand the sample of carefully excavated sites is vital not only for resolving uncertainties in modern human origins, but also for illuminating many other outstanding problems in human evolution.