Jayne Wilkins

Over the last few decades, investigations of the southern African Late Pleistocene archeological record have transformed our understanding of Homo sapiens origins and evolution. However, the intensity of research on coastal and near-coastal records has surpassed that in the deep interior. One reason for the geographic bias is the rarity of well-preserved, datable rockshelter sites outside the more mountainous and karstic regions of South Africa. Here, we report stratified Middle Stone Age and Later Stone Age deposits at Ga-Mohana Hill North Rockshelter (GHN), near Kuruman, in the Northern Cape, South Africa. Contrary to a previous report, we show that the archeological deposits are in good context with minimal disturbance based on a detailed fabric analysis of plotted finds. Three dating methods, single-grain optically stimulated luminescence, radiocarbon, and uranium-thorium, indicate that the artifact-bearing deposits date to ~ 105 ka, ~ 31 ka, and ~ 15 ka. Thus, Ga-Mohana Hill North Rockshelter provides an important opportunity to investigate early human adaptation in this semiarid region of southern Africa.

Approximately 74 thousand years ago (ka), the Toba caldera erupted in Sumatra. Since the magnitude of this eruption was first established, its effects on climate, environment and humans have been debated 1 . Here we describe the discovery of microscopic glass shards characteristic of the Youngest Toba Tuff—ashfall from the Toba eruption—in two archaeological sites on the south coast of South Africa, a region in which there is evidence for early human behavioural complexity. An independently derived dating model supports a date of approximately 74 ka for the sediments containing the Youngest Toba Tuff glass shards. By defining the input of shards at both sites, which are located nine kilometres apart, we are able to establish a close temporal correlation between them. Our high-resolution excavation and sampling technique enable exact comparisons between the input of Youngest Toba Tuff glass shards and the evidence for human occupation. Humans in this region thrived through the Toba event and the ensuing full glacial conditions, perhaps as a combined result of the uniquely rich resource base of the region and fully evolved modern human adaptation.

Grassridge Rockshelter is a multicomponent Pleistocene and Holocene archaeological site located in the interior of the Eastern Cape of South Africa, and was originally studied during the late 1970s and early 1980s. The Grassridge Archaeological and Palaeoenvironmental Project (GAPP) initiated new research at Grassridge in 2014, and here we present an overview of our initial excavations and research, with a focus on the Holocene occupations. Preliminary results indicate a more complex occupational and depositional history than previously thought. In addition to relocating the known mid-Holocene occupation , we have identified a previously unrecorded early Holocene occupation , which dates to the end of the Younger Dryas, and a thin flowstone located at the contact between the Holocene and Pleistocene deposits. The Holocene lithic assemblages are characterised by flake-based lithic reduction, primarily on hornfels, with an increase in the frequency and diversity of retouched pieces from the early to mid-Holocene. Ostrich eggshell beads are ubiquitous during both Holocene occupations, and marine shells have also been discovered. The latter are reported from Grassridge for the first time, and indicate a connection with the coast.

The origins of complex projectile weaponry provides insight into cultural and biological changes associated with the origins and spread of modern human populations. Middle Stone Age backed pieces are often thought to be components of such armaments, however our limited understanding of their functional characteristics as projectiles precludes understanding the adaptive problems they may have solved. Despite acknowledgment of raw material differences and intra-assemblage variability, whether variability in backed piece form reflects functional , economic, or stylistic variation has a paucity of empirical support. Here, the functional differences in backed piece form (size and shape) while hafted transversely and obliquely as high-velocity complex projectile armatures are examined. If there are performance tradeoffs simply in how backed pieces are arranged at the end of armaments that can influence effectiveness, then identifying the archaeological arrangement can provide insight into what variables were being prioritized in prehistoric technological systems. How variation in backed piece size, elongation, and hafting arrangement influences complex projectile performance is tested using experimental and actualistic projectile replications with a calibrated crossbow against animal and ballistics gelatin targets. The results of this study show that, within the size and shape variation of silcrete backed pieces examined , tool form plays a relatively limited role in their performance as projectile armatures. However, hafting orientation has very different performance characteristics for complex projectiles shot at ballistics gelatin compared to animal targets. We demonstrate that transversely hafted tools have more lethal internal wounds, but obliquely hafted backed pieces have greater puncture reliability. These functional differences represent different technological design emphasis: transversely hafted tools create large, deep wounds, while obliquely hafted arrows and darts create a puncture more reliably. Although obliquely hafted armaments cause less internal trauma, they are more likely to penetrate the hide of ungulate prey. Variability in MSA hunting tactics may have played a role in the design of weapon systems to optimize these performance tradeoffs. Despite similarities in shape with ethno-historic technologies, based on these results, MSA-sized backed pieces hafted as projectile armatures were unlikely to have been used with small, low-powered bows-but would have been lethal with a high-velocity delivery system.

There are multiple hypotheses for human responses to glacial cycling in the Late Pleisto-cene, including changes in population size, interconnectedness, and mobility. Lithic technological analysis informs us of human responses to environmental change because lithic assemblage characteristics are a reflection of raw material transport, reduction, and discard behaviors that depend on hunter-gatherer social and economic decisions. Pinnacle Point Site 5–6 (PP5-6), Western Cape, South Africa is an ideal locality for examining the influence of glacial cycling on early modern human behaviors because it preserves a long sequence spanning marine isotope stages (MIS) 5, 4, and 3 and is associated with robust records of paleoenvironmental change. The analysis presented here addresses the question, what, if any, lithic assemblage traits at PP5-6 represent changing behavioral responses to the MIS 5-4-3 interglacial-glacial cycle? It statistically evaluates changes in 93 traits with no a priori assumptions about which traits may significantly associate with MIS. In contrast to other studies that claim that there is little relationship between broad-scale patterns of climate change and lithic technology, we identified the following characteristics that are associated with MIS 4: increased use of quartz, increased evidence for outcrop sources of quartzite and silcrete, increased evidence for earlier stages of reduction in silcrete, evidence for increased flaking efficiency in all raw material types, and changes in tool types and function for silcrete. Based on these results, we suggest that foragers responded to MIS 4 glacial environmental conditions at PP5-6 with increased population or group sizes, 'place provisioning', longer and/or more intense site occupations, and decreased residential mobility. Several other traits, including silcrete frequency, do not exhibit an association with MIS. Backed pieces, once they appear in the PP5-6 record during MIS 4, persist through MIS 3. Changing paleoenviron-ments explain some, but not all temporal technological variability at PP5-6.

The Middle Stone Age (MSA) is associated with early evidence for symbolic material culture and complex technological innovations. However, one of the most visible aspects of MSA technologies are unretouched triangular stone points that appear in the archaeological record as early as 500,000 years ago in Africa and persist throughout the MSA. How these tools were being used and discarded across a changing Pleistocene landscape can provide insight into how MSA populations prioritized technological and foraging decisions. Creating inferential links between experimental and archaeological tool use helps to establish prehistoric tool function, but is complicated by the overlaying of post-depositional damage onto behaviorally worn tools. Taphonomic damage patterning can provide insight into site formation history, but may preclude behavioral interpretations of tool function. Here, multiple experimental processes that form edge damage on unretouched lithic points from taphonomic and behavioral processes are presented. These provide experimental distributions of wear on tool edges from known processes that are then quantitatively compared to the archaeological patterning of stone point edge damage from three MSA lithic assem-blages—Kathu Pan 1, Pinnacle Point Cave 13B, and Die Kelders Cave 1. By using a model-fitting approach, the results presented here provide evidence for variable MSA behavioral strategies of stone point utilization on the landscape consistent with armature tips at KP1, and cutting tools at PP13B and DK1, as well as damage contributions from post-depositional sources across assemblages. This study provides a method with which landscape-scale questions of early modern human tool-use and site-use can be addressed.

Rots and Plisson (2014) question our conclusion that 500,000-year-old points from Kathu Pan 1, South Africa were used as spear tips (Wilkins et al., 2012). However, their reinterpretation of the fractures we identify as diagnostic impact fractures are incorrect. Despite the assertion, knapping processes alone do not explain the basal modifications on the KP1 points. Although Rots and Plisson are critical of the edge damage distribution method, it provides objective, quantitative and statistical comparisons of experimental and archaeological datasets. The data we present stand as reliable evidence for early hafted hunting technology. We suggest that the disagreement stems from a differing perspective on how lithic functional studies should deal with equifinality and the challenge of confidently assessing stone tool function.

Stone-tipped weapons were a significant innovation for Middle Pleistocene hominins. Hafted hunting technology represents the development of new cognitive and social learning mechanisms within the genus Homo, and may have provided a foraging advantage over simpler forms of hunting technology, such as a sharpened wooden spear.  However, the nature of this foraging advantage has not been confirmed. Experimental studies and ethnographic reports provide conflicting results regarding the relative importance of the functional, economic, and social roles of hafted hunting technology. The controlled experiment reported here was designed to test the functional hypothesis for stone-tipped weapons using spears and ballistics gelatin. It differs from previous investigations of this type because it includes a quantitative analysis of wound track profiles and focuses specifically on hand-delivered spear technology. Our results do not support the hypothesis that tipped spears penetrate deeper than untipped spears. However, tipped spears create a significantly larger inner wound cavity that widens distally. This inner wound cavity is analogous to the permanent wound cavity in ballistics research, which is considered the key variable affecting the relative ‘stopping power’ or ‘killing power’ of a penetrating weapon. Tipped spears conferred a functional advantage to Middle Pleistocene hominins, potentially affecting the frequency and regularity of hunting success with important implications for human adaptation and life history.

Hafting stone points to spears was an important advance in weaponry for early humans. Multiple lines of evidence indicate that ~500,000-year-old stone points from the archaeological site of Kathu Pan 1 (KP1), South Africa, functioned as spear tips. KP1 points exhibit fracture types diagnostic of impact. Modification near the base of some points is consistent with hafting. Experimental and metric data indicate that the points could function well as spear tips. Shape analysis demonstrates that the smaller retouched points are as symmetrical as larger retouched points, which fits expectations for spear tips. The distribution of edge damage is similar to that in an experimental sample of spear tips and is inconsistent with expectations for cutting or scraping tools. Thus, early humans were manufacturing hafted multicomponent tools ~200,000 years earlier than previously thought.

This paper explores the effect of taphonomic processes on 500-thousand-year-old stone points from Kathu Pan 1, South Africa by statistically comparing archaeological edge damage distributions on the points to competing models of edge damage formation. We found that both taphonomic and behavioral processes influenced edge damage formation on the KP1 points, and the KP1 edge damage distribution is best explained by a combination of taphonomic effects and use as spear tips. The edge damage distribution method employed here advances studies of Stone Age weaponry because it can be used to quantitatively assess the effect of taphonomic and behavioral processes on stone tips without relying on subjective evaluations that attribute causation to individual wear features.

This methodology is now published as Supporting Information in Wilkins et al., 2017, Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point Site 5-6, South Africa. Plos One. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0174051