Search

For at least three million years, knapping stone has been practiced by hominin societies large and small, past and present. Thus, understanding knapping, knappers, and knapping cultures is fundamental to anthropological research around the world. Although there is a general sense that stone knapping is inherently dangerous and can lead to injury, little is formally, specifically, or systematically known about the frequency, location, or severity of knapping injuries. Toward this end, we conducted a 31-question survey of modern knappers to better understand knapping risks. Responses from 173 survey participants suggest that knapping injuries are a real and persistent hazard, even though a majority of modern knappers use personal protective equipment. A variety of injuries (lacerations, punctures, aches, etc.) can occur on nearly any part of the body. The severity of injury sustained by some of our participants is shocking, and nearly one-quarter of respondents reported having sought or received professional medical attention for a flintknapping-related injury. Overall, the results of this survey suggest that there would have likely been serious, even fatal, costs to knappers in past societies. Such costs may have encouraged the deployment of any social learning capacities possessed by hominins or delayed the learning or exposure of young infants or children to knapping.

Levallois points are a prominent part of many Levantine Middle Paleolithic assemblages. They are either produced intentionally or incidentally by the Levallois core reduction technique and are of a generally similar shape, although the degree to which they were used as specialized tools has been questioned. Here, we examine Levallois points using geometric morphometric analyses to assess the range of shape variation in this artifact type. We then compare Levallois point shape variation and symmetry to a sample of Late Pleistocene-aged Folsom projectile points from North America. Folsom are highly standardized projectile points that current evidence suggests were primarily used for hunting ancient bison. Our results indicate that Levallois points are more variable and asymmetrical than Folsom and therefore more generalized than Folsom. Differences in manufacturing technique, hafting, and delivery system when used as weapons are posited as playing roles in the differences in shape and symmetry that we document. Introduction Materials and methods - Point samples - Geometric morphometric procedures - Statistical analyses Results - Levallois point shape variation - Comparison of Levallois points with Folsom - Symmetry of Levallois and Folsom points Discussion

Before Europeans arrived to Eastern North America, prehistoric, indigenous peoples experienced a number of changes that culminated in the development of sedentary, maize agricultural lifeways of varying complexity. Inherent to these lifeways were several triggers of social stress including population nucleation and increase, intergroup conflict (warfare), and increased territoriality. Here, we examine whether this period of social stress co-varied with deadlier weaponry, specifically, the design of the most commonly found prehistoric archery component in late pre-contact North America: triangular stone arrow tips (TSAT). The examination of modern metal or carbon projectiles, arrows, and arrowheads has demonstrated that smaller arrow tips penetrate deeper into a target than do larger ones. We first experimentally confirm that this relationship applies to arrow tips made from stone hafted onto shafts made from wood. We then statistically assess a large sample (n = 742) of late pre-contact TSAT and show that these specimens are extraordinarily small. Thus, by miniaturizing their arrow tips, prehistoric people in Eastern North America optimized their projectile weaponry for maximum penetration and killing power in warfare and hunting. Finally, we verify that these functional advantages were selected across environmental and cultural boundaries. Thus, while we cannot and should not rule out stochastic, production economizing, or non-adaptive cultural processes as an explanation for TSAT, overall our results are consistent with the hypothesis that broad, socially stressful demographic changes in late pre-contact Eastern North America resulted in the miniaturization–and augmented lethality–of stone tools across the region.

Seeman, Morris, and Summers misrepresent or misunderstand the arguments we have made, as well as their own previous work. Here, we correct these inaccuracies. We also reiterate our support for hypothesis-driven and evidence-based research.

Toward the end of the Pleistocene, the world experienced a mass extinction of megafauna. In North America these included its proboscideans—the mammoths and mastodons. Researchers in conservation biology, paleontology, and archaeology have debated the role played by human predation in these extinctions. They point to traces of human butchery, such as cut marks and other bone surface modifications (BSM), as evidence of human-animal interactions—including predation and scavenging, between early Americans and proboscideans. However, others have challenged the validity of the butchery evidence observed on several proboscidean assemblages, largely due to questions of qualitative determination of the agent responsible for creating BSM. This study employs a statistical technique that relies on three-dimensional (3D) imaging data and 3D geometric morphometrics to determine the origin of the BSM observed on the skeletal remains of the Bowser Road mastodon (BR mastodon), excavated in Middletown, New York. These techniques have been shown to have high accuracy in identifying and distinguishing among different types of BSM. To better characterize the BSM on the BR mastodon, we compared them quantitatively to experimental BSM resulting from a stone tool chopping experiment using “Arnold,” the force-calibrated chopper. This study suggests that BSM on the BR mastodon are not consistent with the BSM generated by the experimental chopper. Future controlled experiments will compare other types of BSM to those on BR. This research contributes to continued efforts to decrease the uncertainty surrounding human-megafauna associations at the level of the archaeological site and faunal assemblage—specifically that of the BR mastodon assemblage. Consequently, we also contribute to the dialogue surrounding the character of the human-animal interactions between early Americans and Late Pleistocene megafauna, and the role of human foraging behavior in the latter’s extinction.

Experimental archaeology continues to mature methodologically and theoretically. Around the world, practitioners are increasingly using modern materials that would have been unavailable to prehistoric people in archaeological experiments. The use of a modern material substitute can offer several benefits to experimental method, design, control, replicability, feasibility, and cost, but it should be directly compared to its “traditional” analogue to understand similarities and differences. Here, aluminum is introduced as a substitute for chert in prehistoric ballistics research because, critically, aluminum is safe, inexpensive, easy to process, and it and chert possess densities that differ by less than 4%. The aluminum casting process for replicating stone artifacts is presented, and it is shown that the aluminum castings are essentially identical in form, flake-scar patterning, and mass to their stone counterparts. We then present a proof-of-concept ballistics experiment that demonstrates no difference between aluminum and stone points in terms of target penetration.

For over 3 million years hominins held stone-cutting tools in the hand, gripping the portion of tool displaying a sharp cutting edge directly. During the late Middle Pleistocene human populations started to produce hafted composite knives, where the stone element displaying a sharp cutting edge was secured in a handle. Prevailing archaeological literature suggests that handles convey benefits to tool users by increasing cutting performance and reducing musculoskeletal stresses, yet to date these hypotheses remain largely untested. Here, we compare the cutting performance of hafted knives, ‘basic’ flake tools, and large bifacial tools during two standardized cutting tasks. Going further, we examine the comparative ergonomics of each tool type through electromyographic (EMG) analysis of nine upper limb muscles. Results suggest that knives (1) recruit muscles responsible for digit flexion (i.e. gripping) and in-hand manipulation relatively less than alternative stone tool types and (2) may convey functional performance benefits relative to unhafted stone tool alternatives when considered as a generalised cutting tool. Furthermore, our data indicate that knives facilitate greater muscle activity in the upper arm and forearm, potentially resulting in the application of greater cutting forces during tool use. Compared to unhafted prehistoric alternatives, hafted stone knives demonstrate increased ergonomic properties and some functional performance benefits. These factors would likely have contributed to the invention and widespread adoption of hafted stone knives during the late Middle Pleistocene.

Robert J. Patten passed away suddenly on February 8, 2017. His influence on flintknapping, lithic technology, and archaeology, however, continues on. Here, we review Patten’s life and myriad contributions.

Understanding prehistoric projectile weaponry performance is fundamental to unraveling past humans’ survival and the evolution of technology. One important debate involves how deeply stone-tipped projectiles penetrate a target. Theoretically, all things being equal, projectiles with smaller tip cross-sectional geometries should penetrate deeper into a target than projectiles with larger tip cross-sectional geometries. Yet, previous experiments have both supported and questioned this theoretical premise. Here, under controlled conditions, we experimentally examine fourteen types of stone-tipped projectile each possessing a different cross-sectional geometry. Our results show that both tip cross-sectional area (TCSA) and tip cross-sectional perimeter (TCSP) exhibit a strong, significant inverse relationship with target penetration depth, although TCSP’s relationship is stronger. We discuss why our experimental results support what is mathematically predicted while previous experiments have not. Our results are consistent with the hypothesis that when stone tip cross-sectional geometries become smaller over time in particular contexts, this evolution may be due to the selection of these attributes for increased penetration.

It has long been assumed that Folsom points are more standardized than Clovis points, although an adequate test of this proposition has yet to be undertaken. Here, we address that deficiency by using data from a sample of Folsom and Clovis points recovered from sites across the western United States. We used geometric morphometric techniques to capture point shape and then conducted statistical analyses of variability associated with Clovis and Folsom point bases and blades. Our results demonstrate that Folsom bases and blades are less variable than those on earlier Clovis points, indicating an increase in point standardization during the Early Paleoindian period. In addition, despite published claims to the contrary, Clovis and Folsom point bases are no more variable than blades. Based on these results, we conducted additional analyses to examine the modularity and size of Clovis and Folsom points. The results suggest Clovis points have more integrated base and blade segments than Folsom points. We suggest that several classes of Clovis points—intended for different functions—might have been in use during the Clovis period and that the later Folsom points might have served only as weapon tips, the shape of which were constrained by the fluting process.

Diverse disciplines investigate how muscular tissue (i.e. ‘meat’) responds to being cut and deformed, however, large-scale, empirically robust investigations into these matters are often impractical and expensive. Previous research has used clay as an alternative to meat. To establish whether clay is a reliable proxy for meat, we directly compare the two materials via a series of cutting and projectile tests. Results confirm that the two materials display distinct cutting mechanics, resistance to penetration and are not comparable. Under certain conditions clay can be used as an alternative to meat, although distinctions between the two may lead to experimental limitations.

Palaeolithic stone technologies have never been investigated in terms of how sharpness influences their ability to cut. In turn, there is little understanding of how quickly stone cutting edges blunt, how past populations responded to any consequent changes in performance, or how these factors influenced the Palaeolithic archaeological record. Presented here is experimental data quantitatively detailing how variation in edge sharpness influences stone tool cutting performance. Significant increases in force (N) and material displacement (mm) requirements occur rapidly within early stages of blunting, with a single abrasive cutting stroke causing, on average, a 38% increase in the force needed to initiate a cut. In energetic terms, this equates to a 70% increase in work (J). Subsequent to early stages of blunting we identify a substantial drop in the impact of additional edge abrasion. We also demonstrate how edge (included) angle significantly influences cutting force and energy requirements and how it co-varies with sharpness. Amongst other conclusions, we suggest that rapid reductions in performance due to blunting may account for the abundance of lithic artefacts at some archaeological sites, the speed that resharpening behaviours altered tool forms, and the lack of microscopic wear traces on many lithic implements.

Clovis fluted points are deemed efficient weapon tips for hunting large game, including Pleistocene proboscideans. However, experimental and archaeological studies cast doubt on their effectiveness as hunting weapons. Owing to the broad and thick tip geometry of Clovis points, their penetration depth into a carcass would have been relatively limited, which would have rendered them unlikely to reach the well-protected vital organs of a proboscidean and inflict lethal wounds. Nor do Clovis points display the types of breakage patterns and impact damage that would be expected were they routinely used as hunting weapons for megafauna, especially when compared with Folsom points found in bison kill sites. Our results question the long-assumed effectiveness of Clovis points for dispatching proboscideans; while these may have on occasion been used as weapon tips on proboscidean prey, they likely had other functions as well.

Intentional heat treating of toolstone has been documented to have begun at least by 70 K BP; however, the advantages of such treatment have been debated for decades. There are two schools of thought with regard to its purpose. One, is that it merely reduces the force required for flake propagation. A second is that it also alters flake morphological properties. We systematically tested these hypotheses by generating flakes from cores exposed to three different temperatures (ambient, 300 °C, and 350 °C) using automated propagation procedures that bypassed any human agency. While the force propagation magnitude is altered by heat treatment, the flakes were not. We examined these flakes according to nine measures of morphology. None differed significantly or systematically within the three categories. While our results confirm that heat treatment does reduce the force needed for flake propagation, they also demonstrate that such treatment has no significant effect on major morphological aspects of flake form.

The Nelson stone tool cache was discovered in 2008 in Mount Vernon, Ohio. The cache does not include any diagnostic materials, and independent age control is unavailable. Although aspects of its 164 bifaces are suggestive of a Clovis affiliation – including the occasional occurrence of unmistakable flute scars – nearly all are in the early- to mid-stages of production, there are no definitive finished Clovis fluted points that would make it possible to assign the cache to that time period. To ascertain its cultural affiliation, we undertook a detailed qualitative and quantitative comparison of the Nelson cache bifaces with ones known to be both Clovis and post-Clovis in age. We also conducted geochemical sourcing, ochre analyses, and microwear analysis to understand the context of the cache, regardless of its age and cultural affinity. By some key measures it is consistent with Clovis caches in this region and elsewhere, but the case remains unproven. Nonetheless, if the Nelson cache is from the Clovis period, it is significant that most of its bifaces appear to be made on large flakes, in keeping with Clovis technology in the Lower Great Lakes, and an economically conservative, risk-mitigating strategy that conforms to predictions of human foragers colonizing the area in late Pleistocene times.

The experimental assessment of prehistoric stone-tipped projectile weapons is a productive research area in experimental archaeology. The measurement of projectile velocity in these experiments is vital for establishing validity, ensuring control, and facilitating data analysis. Many studies have made use of the chronograph to measure stone-tipped projectile velocity, but this practice has never been formally tested. This is problematic because chronographs were not designed for such projectiles, which are different in their size, shape, and materials than modern projectiles. Here we assess chronograph measurement accuracy of stone-tipped projectile velocity by employing two control datasets: bullets and modern arrows. We predicted that if the chronograph accurately measured stone-tipped projectile velocity, then kinetic energy values of a modern arrow and a stone-tipped arrow fired from the same compound bow would be similar. Our analysis confirmed this to be the case. However, our analysis unexpectedly revealed that questions regarding chronograph measurement precision remain.

The “Acheulean” is comprised of individual knapping events undertaken by individual hominins. In other words, it is a particular component of hominin behavior that we draw out and amalgamate into a wider “pattern.” The resultant phenomenon (i.e., “the Acheulean”) is an entity that stretches over the space of three continents and spans a time period in excess of one million years. If such an exercise has any merit, it is because it provides a means of comparative (behavioral) analysis over these swathes of time and space. Comparative research can document, measure, and statistically assess temporo-spatial patterns of artifactual variation, and so test hypotheses regarding the character of that variation. However, it does not provide an independent means of examining some of the key phenomena which it is necessary to further understand in order to increase our comprehension of this archaeological legacy. Here, we review and synthesize recent experimental work that we have undertaken, which has specifically investigated some of the factors potentially responsible for the generation and constraint of variation within the Acheulean techno-complex. We examine issues of raw material, copying errors, and their relationship to mechanisms of social learning. Understanding these microevolutionary factors via experiments, we contend, is essential in order to reach a secure understanding of the macroscale phenomenon typically referred to as the “Acheulean.” Moreover, we outline how a “quantitative genetic” framework to these issues provides an essential means of linking these inherent micro- and macro-evolutionary factors into a coherent whole, while also simultaneously reconciling the potential influence of different sources of variation that are part of a temporally and geographically dispersed entity such as the Acheulean.

For many years, intuition and common sense often guided the transference of patterning ostensibly evident in experimental flintknapping results to interpretations of the archaeological record, with little emphasis placed on hypothesis testing, experimental variables, experimental design, or statistical analysis of data. Today, archaeologists routinely take steps to address these issues. We build on these modern efforts by reviewing several important uses of replication experiments: (1) as a means of testing a question, hypothesis, or assumption about certain parameters of stone-tool technology; (2) as a model, in which information from empirically documented situations is used to generate predictions; and (3) as a means of validating analytical methods. This review highlights the important strategic role that stone artifact replication experiments must continue to play in further developing a scientific approach to archaeology.

Over the past several decades, archaeologists, anthropologists, linguists, and others who study cultural phenomena have begun to appreciate that methods developed to reconstruct the evolutionary, or phylogenetic, relationships among biological taxa can be used to create cultural sequences based on heritable continuity. One method in particular is cladistics, which creates hypothetical statements of relatedness—rendered as trees—based on the model and parameters used. To date, cladistics has been used to create phylogenetic orderings of a wide variety of cultural phenomena, including basketry and other textiles, ceramic vessels, stone projectile points, languages, folk tales, manuscripts, residence patterns, and political organization. Here we lay out the basic method of cladistics and show how it has formed the basis for long-term studies of the colonization of eastern North America during the Early Paleoindian period (ca. 13,300–11,900 calendar years before the present). Statement of Significance Archaeologists have long used changes in artifact form to measure the passage of time, the supposition being that if the changes are ordered correctly, a historical sequence of forms is created. This is correct, but oftentimes what archaeologists really want to know is which thing produced another thing as opposed to simply preceding it. This is an evolutionary sequence. Over the past several decades, not only archaeologists but also anthropologists, linguists, and others who study cultural phenomena have begun to use a suite of methods that were developed to reconstruct the evolutionary, or phylogenetic, relationships among biological taxa, one of which is cladistics. This marks a return to the questions on which the founding of much of anthropology rests: the writing of cultural lineages. This return is important to the growth and continued health of archaeology and anthropology because a reconstructed phylogeny helps guide interpretation of the evolution of traits in that it generates hypotheses about the lineages in which those traits arose and under what circumstances. Data availability The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are contained within the paper.

Ronald Mason’s hypothesis from the 1960s that the southeastern United States possesses greater Paleoindian projectile-point diversity than other regions is regularly cited, and often assumed to be true, but in fact has never been quantitatively tested. Even if valid, however, the evolutionary meaning of this diversity is contested. Point diversity is often linked to Clovis “origins,” but point diversity could also arise from group fissioning and drift, admixture, adaptation, or multiple founding events, among other possibilities. Before archaeologists can even begin to discuss these scenarios, it is paramount to ensure that what we think we know is representative of reality. To this end, we tested Mason’s hypothesis for the first time, using a sample of 1,056 Paleoindian points from eastern North America arui employing paradigmatic classification and rigorous statistical tools used in the quantification of ecological biodiversity. Our first set of analyses, which compared the Southeast to the Northeast, showed that the Southeast did indeed possess significantly greater point-class richness. Although this result was consistent with Mason’s hypothesis, our second set of analyses, which compared the Upper Southeast to the Lower Southeast and the Northeast showed that in terms of point-class richness the Upper Southeast > Lower Southeast > Northeast. Given current chronometrie evidence, we suggest that this latter result is consistent with the suggestion that the area of the Ohio, Cumberland, and Tennessee River valleys, as well as the mid-Atlantic coastal plain, were possible initial and secondary “staging areas” for colonizing Paleoindian foragers moving from western to eastern North America.

Proponents of a Solutrean colonization of the New World, and a pre-LGM occupation of North America's Mid-Atlantic region, cite as evidence a bifacially flaked, bi-pointed stone blade allegedly dredged from the continental shelf by the crew of the vessel Cinmar , along with portions of a mastodon skeleton later directly dated to 22,760 ± 90 RCYBP. However, our investigations into the discovery found several significant inconsistencies with respect to what is currently reported in the literature and raise serious questions that must be addressed before the Cinmar artifact can be considered evidence of anything pertinent to archaeology. In this article we present evidence and questions regarding the history of the Cinmar discovery, the location of the Cinmar discovery site, and the nature of the Cinmar vessel itself.

The weaponry technology associated with Clovis and related Early Paleoindians represents the earliest well-defined evidence of humans in Pleistocene North America. We assess the technological diversity of these fluted stone points found at archaeological sites in the western and eastern halves of North America by employing statistical tools used in the quantification of ecological biodiversity. Our results demonstrate that the earliest hunters in the environmentally heterogeneous East used a more diverse set of points than those in the environmentally homogenous West. This and other evidence shows that environmental heterogeneity in the East promoted the relaxation of selective constraints on social learning and increased experimentation with point designs.

The ethnographic account of an Inuit man manufacturing a knife from his own frozen feces to butcher and disarticulate a dog has permeated both the academic literature and popular culture. To evaluate the validity of this claim, we tested the basis of that account via experimental archaeology. Our experiments assessed the functionality of knives made from human feces in controlled conditions that provided optimal conditions for success. However, they were not functional. While much research has shown foragers to be technologically resourceful, innovative, and savvy, we suggest that this ethnographic account should no longer be used to support that narrative.

Archaeologists have attributed the decline of North American utilitarian copper tools to changes in demography and social complexity during the Archaic to Woodland transition, ca. 3000 B.P. However, not all utilitarian copper tools disappeared: the copper awl persisted. Given that the copper tool types that disappeared, such as projectile points and knives, have been experimentally shown to be functionally inferior to their non-copper counterparts, we tested whether the copper awl persisted because it was functionally superior to those made of bone. Using replicated copper and bone awls in a controlled punching experiment that utilized an Instron Universal Materials Tester, we demonstrate that copper awls require significantly less force to punch through leather relative to bone awls. These results strongly support the hypothesis that tool function played an important role in the evolution of the North American copper tool repertoire 3000 B.P.

The notion that Paleoindians used bifaces as “mobile cores” is widespread in Late Pleistocene lithic research, although it can be difficult to test empirically. Here, we use experimental replication to establish two quantitative predictions that would be indicative of biface-core transport. If bifaces are being used as mobile cores, then we should see among a group of sites of varying toolstone procurement distances (a) a negative relationship between toolstone procurement distance and the mean unifacial tool maximum-thickness value from each site; and (b) a negative relationship between toolstone procurement distance and the variability (standard deviation) of maximum flake thickness values from each site. We then test these predictions against data from six Clovis sites of varying toolstone procurement distance in the Lower Great Lakes region. The results show that both sets of data possess a strong, positive relationship with increasing toolstone procurement distance, which is inconsistent with the notion that biface-cores were transported. Since the Clovis presence in the Lower Great Lakes is widely acknowledged to be a colonization pulse, we conclude that the lack of biface-core transport there is an economizing and risk-mitigating behavior consistent with the models of Kuhn (1994) and Meltzer (2002, 2003, 2004).

It has been proposed that Paleolithic studies should abandon their focus on groups and turn instead to the individual. If individuals are to emerge from the lithics-dominated Middle Paleolithic record, the best chance of success is to identify the products of learner knappers from those of their mentors. To do so we need a framework of knapping standards by which to measure Middle Paleolithic skill level. Selected measurements on a sequence of 100 subcircular Levallois tortoise core reductions by a knapper of intermediate skill were compared with 25 reductions by his highly experienced instructor. Four measures emerge as potential markers of skill level: total stone consumption during initial core preparation, consumption from the upper and lower core surface, symmetry of the first detached Levallois flake, and failure rate of that detachment by overshooting the core’s rim. These markers allow us to discriminate between the work of a modern learner and his mentor, but >30 percent were misclassified. The learning trajectory is more complex than the mere honing of skills through practice and is punctuated by increasing numbers of mentor-like reductions. It follows that skill-level measures on their own are imperfect discriminators. Personal markers other than those of skill level must be found by which to seek individuals in the Middle Paleolithic record. Se ha propuesto que los estudios del Paleolitico deberian centrarse en el individuo y no en el grupo social. Una manera de conseguir que el individuo surja del registro del paleolitico medio, que es predominantemente litico, es a traves de la diferenciacion entre productos de talla litica del aprendiz y del maestro. Para ello, es necesario construir un marco referencial de estandares de talla que mida el nivel de destreza requerido para talla durante el paleolitico medio. En este trabajo se han realizado las medidas correspondientes en una secuencia de 100 reducciones de nucleo Levallois de tortuga subcircular llevadas a cabo por un individuo con un nivel intermedio de experiencia. Estas medidas fueron comparadas con 25 reducciones realizadas por el instructor de dicho individuo, quien contaba con un alto nivel de experiencia. Como resultado, se obtuvieron cuatro medidas como marcadores del nivel de experiencia: el consumo total de la piedra durante la preparacion inicial del nucleo, el consumo de la superficie superior e inferior del nucleo, la simetria de la primera lasca levallois, y la tasa de error de dicha extraccion al sobrepasar el borde del nucleo. Estos marcadores nos permiten discriminar entre el trabajo de un principiante y su maestro en la actualidad; sin embargo, >30% quedan fuera de esta clasificacion. La trayectoria de aprendizaje comporta mas complejidad que la mera acumulacion de destreza a partir de la practica, manifestandose a traves de un aumento en el numero de extracciones de experto. Se deduce que las medidas del nivel de destreza porsisolasson discriminantesimperfectos para identificar al individuo. Para llegar a reconocer al individuo en el registro del paleolitico medio se deben reconocer marcadores personales adicionales aparte del nivel de destreza

This paper presents the motivation, procedures, and results of an experiment that examines short episodes of animal trampling in dry and water saturated substrates in South India. While horizontal artifact displacement was similar to that modeled by other trampling experiments, vertical artifact displacement in water saturated substrates was greater than any reported experiment to date. The toolstone used in this experiment, a silicious limestone, exhibited minimal damage after trampling. Artifact inclination patterning appeared to be a potentially diagnostic middle-range marker of trampling in water saturated substrates. Given the abundant number of Paleolithic sites that are located on flat, open surfaces near water-bodies, or experience monsoonal climatic regimes, we propose that future excavations should measure artifact inclination on a regular basis.

A long-standing debate in Pleistocene archaeology concerns the sources of variation in the technology of colonizing hunter-gatherers. One prominent example of this debate is Clovis technology (13,350–12,500 calendar years before present), which represents the earliest widespread and currently recognizable remains of hunter-gatherers in North America. Clovis projectile points appear to have been made the same way regardless of region, but several studies have documented differences in shape that appear to be regional. Two processes have been proposed for shape variation: (1) stochastic mechanisms such as copy error (drift) and (2) Clovis groups adapting their hunting equipment to the characteristics of prey and local habitat. We used statistical analysis of Clovis-point flake-scar pattern and geometric morphometrics to examine whether drift alone could cause significant differences in the technology of Stone Age colonizing hunter-gatherers. Importantly, our analysis was intraregional to rule out a priori environmental adaptation. Our analysis confirmed that the production technique was the same across the sample, but we found significant shape differences in Clovis point populations made from distinct stone outcrops. Given that current archaeological evidence suggests stone outcrops were “hubs” of regional Clovis activity, our dichotomous, intraregional results quantitatively confirm that Clovis foragers engaged in two tiers of social learning. The lower, ancestral tier relates to point production and can be tied to conformist transmission of tool-making processes across the Clovis population. The upper, derived tier relates to point shape, which can be tied to drift that resulted from increased forager interaction at different stone-outcrop hubs and decreased forager interaction among groups using different outcrops. Given that Clovis artifacts represent the earliest widespread and currently recognizable remains of hunter-gatherers in North America, our results suggest that we need to alter our theoretical understanding of how quickly drift can occur within a colonizing population and create differences among socially learned technological characters.