Stephen J. Lycett

On questions surrounding the Acheulean ‘tradition’

Abstract The Acheulean, sometimes known as ‘the great handaxe tradition’, is the longest-lasting entity in the human cultural record. The oldest sites are in Africa at around 1.6 million years ago and the most recent approach the last 100,000 years. The geographical extent is also enormous, ranging across Africa, the Middle East, most of Europe and large parts of Asia. Is it however a real tradition? The Acheulean represents a set of stone-working ideas that endure, but the strength of ‘tradition’ is often an assumption made by archaeologists. This paper re-examines Acheulean biface variation, looking at sets of assemblages measured in different ways, but amenable to discriminant analysis (DFA), which is able to highlight differences useful in classification. The analyses show significant differences between European and African assemblages. In the case of the Far East, in line with others, we provide further analyses suggestive of technological differences between putative ‘handaxes’ from Korea and some ‘classic’ western assemblages. However, it is not yet fully clear how far a ‘typical’ Acheulean tradition is represented, as matching of Far Eastern assemblages to other parts of the world depends to an extent upon the criteria used. With regard to the more general Acheulean paradox, the paper notes parallels in biological studies with the idea that a single widely extending phenomenon can incorporate elements of both unity and diversity.

Phylogenetic analyses of behavior support existence of culture among wild chimpanzees

Culture has long been considered to be not only unique to humans, but also responsible for making us qualitatively different from all other forms of life. In recent years, however, researchers studying chimpanzees (Pan troglodytes) have challenged this idea. Natural populations of chimpanzees have been found to vary greatly in their behavior. Because many of these interpopulation differences cannot be readily explained by ecological factors, it has been argued that they result from social learning and, therefore, can be regarded as cultural variations. Recent studies showing social transmission in captive chimpanzee populations suggest that this hypothesis is plausible. However, the culture hypothesis has been questioned on the grounds that the behavioral variation may be explained at a proximate level by genetic differences between subspecies. Here we use cladistic analyses of the major cross-site behavioral data set to test the hypothesis that the behavioral differences among the best-documented chimpanzee populations are genetically determined. If behavioral diversity is primarily the product of genetic differences between subspecies, then population data should show less phylogenetic structure when data from a single subspecies (P. t. schweinfurthii) are compared with data from two subspecies (P. t. verus and P. t. schweinfurthii) analyzed together. Our findings are inconsistent with the hypothesis that the observed behavioral patterns of wild chimpanzee populations can be explained primarily by genetic differences between subspecies. Instead, our results support the suggestion that the behavioral patterns are the product of social learning and, therefore, can be considered cultural.

The Movius Line controversy: the state of the debate

Abstract Patterns of Palaeolithic variability between eastern Asia and western portions of the Old World continue to engender controversial discussion. Most famously, debate has focused on variability in the absence/presence of ‘handaxes’ east and west of the so-called ‘Movius Line’. However, it is becoming equally apparent that cross-regional contrasts can be made using categories of data other than handaxe presence/absence alone. This, in turn, is leading to a reconfiguration of the archaeological patterns that demand explanation. Here, we outline the current state of the Movius Line controversy in these terms, and undertake a series of metric analyses of eastern and western biface samples. This leads us to highlight specific lines of enquiry that may be important for future attempts to address these enduring questions.

Copying Error and the Cultural Evolution of “Additive” vs. “Reductive” Material Traditions: An Experimental Assessment

Abstract Copying errors that occur during the manufacture of artifactual traditions are potentially a major source of variation. It has been proposed that material items produced via “additive” processes (e.g., pottery) will possess less variation than traditions produced via “reductive” processes (e.g., stone knapping). The logic of this premise is that “additive” production methods more readily allow for the reversal of copying errors compared to strictly “reductive-only” processes. Here, we tested this hypothesis in shape data using an experimental framework in which we generated and statistically analyzed morphometry (size-adjusted) shape data under controlled and replicable conditions. Participants engaged in one of two alternative conditions: an irreversible (“reductive-only”) manufacturing process or a reversible (“additive-reductive”) process. With a number of factors held constant, participants were required to copy the shape of a “target form” as accurately as possible using a standardized block of plasticine and a steel table knife. Results demonstrated statistically greater levels of shape-copying errors in the replicas produced in the reductive-only condition. This indicates that “mutation rates” in the shape attributes of artifactual traditions produced via reductive processes are inherently greater than those produced via alternative means. Several implications for the study of variation in artifactual traditions are discussed.

From cultural traditions to cumulative culture: parameterizing the differences between human and nonhuman culture

Diverse species exhibit cultural traditions, i.e. population-specific profiles of socially learned traits, from songbird dialects to primate tool-use behaviours. However, only humans appear to possess cumulative culture, in which cultural traits increase in complexity over successive generations. Theoretically, it is currently unclear what factors give rise to these phenomena, and consequently why cultural traditions are found in several species but cumulative culture in only one. Here, we address this by constructing and analysing cultural evolutionary models of both phenomena that replicate empirically attestable levels of cultural variation and complexity in chimpanzees and humans. In our model of cultural traditions (Model 1), we find that realistic cultural variation between populations can be maintained even when individuals in different populations invent the same traits and migration between populations is frequent, and under a range of levels of social learning accuracy. This lends support to claims that putative cultural traditions are indeed cultural (rather than genetic) in origin, and suggests that cultural traditions should be widespread in species capable of social learning. Our model of cumulative culture (Model 2) indicates that both the accuracy of social learning and the number of cultural demonstrators interact to determine the complexity of a trait that can be maintained in a population. Combining these models (Model 3) creates two qualitatively distinct regimes in which there are either a few, simple traits, or many, complex traits. We suggest that these regimes correspond to nonhuman and human cultures, respectively. The rarity of cumulative culture in nature may result from this interaction between social learning accuracy and number of demonstrators.

Test, Model, and Method Validation: The Role of Experimental Stone Artifact Replication in Hypothesis-driven Archaeology

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.

The interaction of neutral evolutionary processes with climatically-driven adaptive changes in the 3D shape of the human os coxae.

Differences in the breadth of the pelvis among modern human populations and among extinct hominin species have often been interpreted in the light of thermoregulatory adaptation, whereby a larger pelvic girdle would help preserve body temperature in cold environments while a narrower pelvis would help dissipate heat in tropical climates. There is, however, a theoretical problem in interpreting a pattern of variation as evidence of selection without first accounting for the effects of neutral evolutionary processes (i.e., mutation, genetic drift and migration). Here, we analyse 3D configurations of 27 landmarks on the os coxae of 1494 modern human individuals representing 30 male and 23 female populations from five continents and a range of climatic conditions. We test for the effects of climate on the size and shape of the pelvic bone, while explicitly accounting for population history (i.e., geographically-mediated gene flow and genetic drift). We find that neutral processes account for a substantial proportion of shape variance in the human os coxae in both sexes. Beyond the neutral pattern due to population history, temperature is a significant predictor of shape and size variation in the os coxae, at least in males. The effect of climate on the shape of the pelvic bone, however, is comparatively limited, explaining only a small percentage of shape variation in males and females. In accordance with previous hypotheses, the size of the os coxae tends to increase with decreasing temperature, although the significance of the association is reduced when population history is taken into account. In conclusion, the shape and size of the human os coxae reflect both neutral evolutionary processes and climatically-driven adaptive changes. Neutral processes have a substantial effect on pelvic variation, suggesting such factors will need to be taken into account in future studies of human and fossil hominin coxal variation.

Reassessing the production of handaxes versus flakes from a functional perspective

Bifacially flaked stone tools, traditionally referred to as “handaxes” were produced by Pleistocene hominins for over one million years over three different continents. This spatial and temporal prevalence raises questions about the factors that may have motivated their use as supplements to more simple flake tools. Hence, understanding the comparative functional performance capabilities of flakes and handaxes is essential to understanding factors that may have motivated the repeated production of handaxes during the Pleistocene. Here, we examine this question using a larger scale experimental approach than has previously been undertaken. We statistically assessed the comparative functional efficiencies of basic flake cutting tools and handaxes when undertaking a series of distinct cutting tasks. Furthermore, for the first time, we examined the functional capabilities of flake tools that are of equal size and mass to handaxes. Our results identify that the specific material context in which these tools are used is key to their relative functional efficiencies, with basic flake cutting tools being significantly more efficient than handaxes when undertaking relatively small, precise cutting tasks. Alternatively, we identify that handaxes are significantly more efficient than basic flake cutting tools when tasked with cutting relatively large, resistant portions of material. Thus, we conclude the adoption and widespread production of handaxes by Pleistocene hominins was motivated, at least in part, by requirements to undertake this specific type of task, rather than them being inherently superior to flakes in all cutting tasks. Indeed, interestingly, the comparative functional efficiencies of handaxes and flakes of equal size are far less pronounced than expected, with a number of tasks displaying no significant efficiency differences. Subsequently, we stress that a number of other hypothesized advantages of handaxes may have also been key to their widespread production and use by Pleistocene hominins.

Are human hands and feet affected by climate? A test of Allen's rule

OBJECTIVES In recent years, several studies have shown that populations from cold, high-latitude regions tend to have relatively shorter limbs than populations from tropical regions, with most of the difference due to the relative length of the zeugopods (i.e., radius, ulna, tibia, fibula). This pattern has been explained either as the consequence of long-term climatic selection or of phenotypic plasticity, with temperature having a direct effect on bone growth during development. The aims of this study were to test whether this pattern of intra-limb proportions extended to the bones of the hands and feet, and to determine whether the pattern remained significant after taking into account the effects of neutral evolutionary processes related to population history. MATERIALS AND METHODS Measurements of the limb bones, including the first metatarsal and metacarpal, were collected for 393 individuals from 10 globally distributed human populations. The relationship between intra-limb indices and minimum temperature was tested using generalized least squares regression, correcting for spatial autocorrelation. RESULTS The results confirmed previous observations of a temperature-related gradient in intra-limb proportions, even accounting for population history. This pattern extends to the hands, with populations from cold regions displaying a relatively shorter and stockier first metacarpal; however, the first metatarsal appears to be wider but not shorter in cold-adapted populations. DISCUSSION The results suggest that climatic adaptation played a role in shaping variation in limb proportions between human populations. The different patterns shown by the hands and feet might be due to the presence of evolutionary constraints on the foot to maintain efficient bipedal locomotion.

Differing Patterns of Material Culture Intergroup Variation on the High Plains: Quantitative Analyses of Parfleche Characteristics VS. Moccasin Decoration

Native American communities occupying the western Great Plains during the postcontact period exemplify the highly contingent relationships between artifactual data and cultural processes. Here, cultural evolutionary theory and quantitative analyses are used to approach this challenge. Two sets of artif actual products were examined: parfleche attributes and moccasin decorative features, both products of female craftswomen.A model of “isolation by distance “ drawn from population genetics is used as a baseline expectation. This model predicts that, all else being equal, between-group geographic relationships will correlate with intergroup patterns of artif actual variation. Linguistic affinity and known patterns of intertribe alliance and hostility were also examined. The analyses reveal the operation of differing degrees of social transmission and differing patterns of selective bias in each artif actual case. In the case of parfleches, their potential to act as visible signals led to a patterned distribution reflecting intertribe alliance and hostility. The analyses reiterate the necessity of a cultural evolutionary approach to material culture, not only because this method facilitates the requisite flexibility toward particular historical trajectories of artifactual lineages, but also because evolutionary principles provide a range of theoretical models and practical tools of analysis, which facilitate an empirical and quantitatively analytical approach to this problem.