Late Acheulian multiplicity in manufactured stone culture at the end of the Middle Pleistocene in Western Europe

Abstract

In Prehistory, Paleolithic stone toolkits are allotted to distinct cultural phases, explained through a periodization that has been adopted as a strategic reference by specialists in lithic studies, based on: 1) the categorization of morpho-types observed in the assemblages; 2) the dominant manufacture technologies and 3) temporal categorizations based on geo-archeological data. Significant changes in toolkits are observed through time, signaling variations in extinct hominin behavioral configurations. They characterize the denominative classifications of the techno-complexes, presently defined under consensus. Applying the Homogeneity, Variability, Diversity, Multiplicity (HVDM) paradigm as a conceptual scheme for understanding the structural evolution of human technologies, we define the Multiplicity phase, exploring the techno-social consequences of changes materialized in the Late Acheulian of Western Europe, presaging the Middle Paleolithic world of the Neandertals and the arrival on the scene of our own species; Homo sapiens. During this period, in Western Europe, Homo heidelbergensis was undergoing biological transformations, which appear to have fused into a range of hominin forms, raising questions of intra-species contacts and cultural exchange on a backdrop of branching evolutionary configurations. Beyond handaxe production, this period is marked by significant social and behavioral revolutions: changes in landscape use, high population mobility and inter-connectivity, tool-type diversity, technological innovations, as well as the expansion of distinct hominin clades throughout the Old World. We examine the impulses for these changes, in particular, the prominent role played by the mastery of fire in revolutionizing human socialization processes.

Introduction

This paper presents the fourth and final phase of the “Homogeneity, Variability, Diversity and Multiplicity Model (HVDM model), a structural paradigm developed by Carbonell et al. (2009) as an alternative approach to understanding the evolution of human technologies throughout the Pleistocene and the development of distinct cultural units that appeared, muted and were diffused over vast geographical expanses through time. The model is already in use to illustrate how the analysis of stone tool assemblages can provide insights into the evolutionary systemic of human behaviors and the cognitive levels they reflect (Carbonell et al., 2016; Barsky et al., 2018, 2019). It is proposed as a deviation from the traditional classificatory constructs composing the foundations of typological analysis (Bordes, 1961) and as an alternative conceptual framework for understanding technological change observed in ancient lithic toolkits. Undeniably, seemingly ineluctable typological classificatory systems continue to permeate even the most progressive technological interpretations, in particular for the Middle and Upper Paleolithic records, which remain, nevertheless, deeply entrenched in such notions as relative tool-type frequencies and (even still) fossil directors (François Bordes: presence of particular tool types found in archeological horizons as signals for specific cultural entities and chronologies). Of course, the complementary vision provided by technological analysis, especially after the 1990s, engaging the milestone notion of chaîne opératoire (Eng. operative scheme or reduction sequence; Soressi and Geneste, 2011 and references) greatly enlarged the field of view provided by stone toolkits and the range of data potentially gleaned from them. Today, innovative new equipment and expertise contribute to establishing ever-more diverse areas of study, enhancing results obtained in the field of lithic analysis, for example: computerized spatial distribution and refitting studies or geometric morphometric investigations supported by 3D digital imagery of lithic tools (Lycett, 2009; Shott, 2014; García-Medrano et al., 2018; Grosman et al., 2014; Herzlinger and Grosman, 2018; Titton et al., 2020), as well as progressing use-wear studies combining methodologies supported by high-powered microscopy and laser procedures for residue analysis (Ollé and Vergès, 2013; Caricola et al., 2018; Borel et al., 2014; Ollé et al., 2016; Rots et al., 2016; Hayes et al., 2018; Martín-Viveros and Ollé, 2020; Pedergnana et al., 2020), among others. Over time, all of this has allowed lithic studies to move beyond (but not abandon) its classical typological methodologies and to appreciate the pitfalls of applying unilateral approaches to something as complex as prehistoric cultural categorizations. It is now clear that, in order to distinguish boundaries (both cognitive and physical) that may actually exist and be defined and classified into distinct techno-complexes, we must not limit ourselves to pigeonholing lithic records by assembling together analogous morphologies of the different items they contain and imbuing them with chrono-cultural meaning.

By calling upon an array of different approaches, models and concepts in lithic studies (Clark, 1969; Isaac, 1972, 1977, 1983, 1986; Carbonell et al., 1992; 2009; Leakey, 1971; Shea, 2013; Boëda, 2013, etc.), we continue to move forward in our understanding of hominin lifeways and their evolution through time. Indeed, it seems that our own understanding does preclude some kind of categorization, in order to make sense of our observations, even while we struggle to avoid subjectivity. Culture evolves. We may all concede that, notwithstanding its diachronic character, human cultural evolution-interpreted from lithic toolkits in the Prehistoric register –occurs with a clearly recognizable and exponential tendency towards greater technical complexity and heterogeneity; since its perceptible emergence more than 3 Ma in Africa (Harmand et al., 2015) up to the present day. Toolmaking, while no longer considered the exclusive domain of the genus Homo, certainly seems have become a behavior that was more fully integrated into the lifeways of this genus (H. habilis, Villmoare et al., 2015) with Oldowan toolkits appearing around 2.6 Ma (Braun et al., 2019; Semaw et al., 2000). Considered thus as a behavioral trait, tool making might have been invented, re-invented, and transmitted by successive (and often coeval) hominin species along the evolutionary highway (de la Torre, 2019). In any case, the archeological record shows clearly that, through time, tool making became ever more massively adopted as a survival strategy by all succeeding representatives of the genus Homo, as species’ members became increasingly dependent upon it through time. In its early stages, this process is understandable by the ostensible advantages that tools would have provided to hominins adopting this strategy for obtaining resources, enabling them to carve-out their own niche in relation to other large carnivores and in an ever-widening range of contexts. Furthermore, tool making enabled hominins to reduce the time spent in fulfilling the most basic of survival necessities; beginning with obtaining foodstuffs-in particular high protein-yielding meats and viscera. In the archeological record, this circumstance is reflected in the gradual increase in brain size, observed first and foremost in Homo habilis, relative to earlier hominin forms, and then in subsequent species of Homo as we move through time (Foley and Lee, 1991; Burini and Leonard, 2018). Nowadays, relatively numerous sites attributed to the Oldowan techno-complex attest that the lithic assemblages are often found in association with large herbivore fossils bearing traces of percussion and cut marks made by stone tool-using hominins (Fejej Fj-1a, Barsky et al., 2011; FLK Zinj site, Bed I, Olduvai Gorge, Domínguez-Rodrigo, 2009; Domínguez-Rodrigo and Barba, 2006).

Demographic growth appears to have accelerated notably after around 1.5 Ma and onwards into the Acheulian, as attested by a steady proliferation in the number of sites, as well as in the density of archeological materials they comprise. After around 2 Ma, first Homo expanded into different territories/continents, suggesting enhanced survival capacities impacting on reproductive success (Tanzania, Leakey, 1973; Johanson et al., 1987; Tobias, 1991; South Africa, Ackermann et al., 2012; Kenya, Hill et al., 1992) that (we propose) reflects advantages reaped from their increasingly heavy investment in toolmaking and tool using. Looking to the larger picture of evolutionary tendencies, we find signs of augmented heterogeneity within the toolkits themselves-both on the technological and typological levels -from the so-called ‘Developed Oldowan’ (ca. 1.8 Ma, Leakey, 1971) or ‘Early Acheulian’ (de la Torre and Mora, 2014), marked by the recurrence of some distinctive artifact types (i.e. spheroids/sub-spheroids, retouched flakes, clearly configured macro-tools). During an early phase of the Acheulian (generally attributed to Homo ergaster and Homo erectus), Large Flake-based toolkits containing a range of new and standardized tools (Large Flake Acheulian or LFA, Sharon, 2009) came to be made by sophisticated production technologies, (after 1.75 Ma, Lepre et al., 2011; Beyene et al., 2013), undoubtedly reflecting a broadening range of activities. This underpins the fact that new technologies were being used to manufacture tools in accordance to specific mental templates with a clear orientation towards reproducing standardized morphologies (Sharon, 2011). It further signals the beginnings of new forms of socialization actually linked to the establishment of technical traditions for the production of recurrent tool forms. In addition, hominins began to make tools whose attributes were not necessarily linked to functional criteria (i.e. symmetrical bifaces).

We argue that it is precisely this aspect that triggered new notions of custom and tradition-the building blocks of culture -projecting toolmaking far beyond its initial role of simple survival strategy and into the realm of complex- and even symbolic -social practices. Among the most remarkable features occurring towards the end of the long evolutionary trajectory of the Acheulian (MIS 12), was the upsurge in the adaptive range of our genus (Homo erectus and derivative forms), whose technological prowess finally rendered it capable of thriving in ever more diverse ecosystems (Parfitt et al., 2010; Ashton and Lewis, 2012; Moncel et al., 2018). Migrating durably into new territories, Late Acheulian hominins expanded and solidified their cultural multiplicity into a highly significant, eco-social evolutionary trait of the human clade. In our analysis, it is important to consider the cognitive capacities of hominins that gave rise to the variability and diversity of tools found in archeological sites. From the biological point of view, the qualitative leap towards a vision of the properties of the raw material and the benefits related to its conscious alteration could be related to the diffusion within the hominin population of certain genetic changes. According to Dennis et al. (2012), the SRGAP2 gene (silt-Robo Rho GTPase-activing protein 2) underwent a duplication about three to four million years ago, coinciding with the transition between Australopithecus and Homo and the appearance of the first tools. Of course, this hypothesis is speculative, because it is not possible to establish a direct relationship between one phenomenon and the other. Two new duplications of the gene would have occurred between 2.4 and 1.0 million years ago, probably coinciding with the expansion of the brain in the genus Homo. However, this gene does not seem to cause an increase in brain volume, but rather a greater connectivity between neurons (Charrier et al., 2012). Other researchers (Suzuki et al., 2018) have pointed out that the activation of the gene NOTCH2NL (located on chromosome 1) could be the mechanism that triggered the increase in brain size in the genus Homo about three million years ago. These are two examples of the attempt to link changes in the genome with increased cognitive abilities in hominins.

However, we are aware that it is not possible to establish a direct relationship between increased brain size and cultural complexity. Estimates of the encephalization quotient (Ruff et al., 1997), which relate brain mass and body mass, suggest a long period of stasis of the genus Homo, at least until the middle Middle Pleistocene. Rightmire (2004) goes even further and only finds a significant increase in the encephalization quotient with the appearance of the hominins that he includes in Homo heidelbergensis. In this biological context, there have been qualitative leaps in cultural complexity, without the concomitant leaps in the estimated encephalization quotient. In contrast, increases in the quotient of encephalization do not necessarily imply greater cultural complexity. It is therefore necessary to invoke other factors such as demographic increase and contact between populations or environmental pressure.

Having already applied the HVDM model to explore developmental trends in technology during the earliest periods of the Paleolithic: the emergence and development of the Oldowan (homogeneity and variability; Carbonell et al., 2009, 2018) and into the Developed Oldowan and Early Acheulian (diversity; Carbonell et al., 2016). This paper analyzes the underlying configurations, physical, technical and behavioral, that led to the spread of the Late Acheulian. We examine this cultural phenomenon in the Western European context after around 700 Ka (Sharon and Barsky, 2016), which corresponds with the beginning of the multiplicity phase in Europe (Caune de l’Arago, Notarchirico, La Noira), as discussed in this paper (Barsky, 2013; Moncel et al., 2013, Moncel et al., 2020). Preceding this date, there are few records of the Acheulian techno-complex in Europe (El Barranc de la Boella and US4 of Bois-de-Riquet; Vallverdú et al., 2014; Bourguignon et al., 2016). However, after around 500 Ka, a comparatively wide spread (Roebroeks and van Kolfschoten, 1994) of the Late Acheulian (Sharon and Barsky, 2016) is attested.

In Western Europe, the Late Acheulian (LA) designates the final phase of the Acheulian techno-complex as it extends into the Middle Paleolithic, where it is found to coexist with the first Mousterian cultural facies from MIS 12 to MIS 9-8 (Leroi-Gourhan, 1988; Lumley, 2004; Méndez-Quintas et al., 2019; Key et al., 2021). In the hominin record, this chronological range corresponds with H. heidelbergensis, relatively widely represented throughout Western Europe (Rightmire, 1998) and with the appearance of the Neandertal lineage, whose divergence from the Denisovans is now believed to predate 430 Ka (Meyer et al., 2016) and that appears somehow linked with the European Homo erectus (Lumley, 2018). These Late Acheulian hominins are known to have lived in different types of habitat, including open-air (especially along watercourses), rock shelters and caves. Some sites contain depositional sequences with successive layers that reveal different types of hominin occupations (short, medium or long-term, seasonal, specialized or non-specific hunting, etc., often alternating sporadically with other large carnivores). This feature is indicative of the cyclical return of hominin groups to specific areas-sometimes over thousands of years (Barsky, 2013; Ollé et al., 2013; Saladié et al., 2018; Moncel et al., 2019). LA sites are numerous and they often contain dense or even very dense concentrations of archeological materials. Finds include lithic tools and systematically butchered fauna with profiles typical of selective hunting practices and sometimes displaying markedly high indexes of anthropic intervention (Barsky, 2013; Barsky et al., 2019; Rodríguez-Hidalgo et al., 2017). In addition, evidence for the use of fire is noted at some sites from 400 to 300 Ka (Terra Amata and Menez Dregan in France, Vértesszöllös in Hungary, Beeches Pit in England and Schöningen and Bilzingsleben in Germany, among others), but this behavior is not entirely ubiquitous until somewhat later (Roebroeks and Villa, 2011; Gowlett, 2016), from MIS 11 and especially after 9-8, when we begin to find truly structured hearth areas (Lumley, 2006; Fernández-Peris et al., 2012) and even some multilevel sites with mega-hearth structures (Cueva del Ángel, Barrosso-Ruiz et al., 2011).

Late Acheulian lithic assemblages may or may not contain handaxes (Notter, 2007; Barsky and Lumley, 2010; Lumley, 2015; Moncel et al., 2020) and, apart from sites in Spain and sparse appearances elsewhere in Western Europe, cleavers and LFA technologies are scarcely represented (Bourguignon et al., 2016; Sharon, 2007; Sharon and Barsky, 2016; Santonja and Villa, 2006; Santonja et al., 2016; Santonja and Pérez-González, 2010). Toolkits were made using a wide range of raw materials, coming sometimes from very distant sources and, in consistency with earlier Acheulian traditions; a clear correlation is established between the chosen raw materials and the tool categories (Barsky, 2013). Core knapping systems are divers; oriented towards small to medium-sized flake production. Bifacial discoid (and related) core reduction strategies generally dominate and the cores can be very small-sized, especially compared to previous phases of the Acheulian. Meanwhile, a wide range of other core forms are present (as discussed below), ranging from cubic to globular and pyramidal, always reflecting systematization of the strategies regardless of the matrices' dimensions and raw materials used. Small retouched tools on flakes are very abundant and hardly distinguishable from Mousterian-type retouched toolkits: scrapers abound in proportions that are generally higher than denticulate tools and pointed morphologies are very common. Some ‘relic’ tool types, such as Limaces, as well as Tayac and Quinson points may persist in some assemblages. Cobble tools are ubiquitous, following their own pathways to standardization, including pointed or convergent-edge chopper types, while some macro-tool ‘types’ such as spheroids, disappear or are not represented (Titton et al., 2020). Bone tools and bone retouchers are documented (Villa and d’Errico, 2001; Moigne et al., 2016), notably at some Late Acheulian sites in the Latium region of Italy (Fontana Ranuccio, Castel di Guido; Biddittu and Segre, 1982; Biddittu and Celletti, 2001; Boschian and Saccá, 2010). Comparative intra-site analyses between the toolkits in multi-stratigraphic contexts show subtle variations in the assemblages attributed to various causes: raw material variability, changing site-use contexts (hunting practices, hominin group size and constituent types) and climatic changes through time, that affected landscape and faunal resources (Barsky, 2013; García-Medrano et al., 2015; Lombera-Hermida et al., 2020). Regional variations in these criteria have led prehistorians to recognize and define ‘traditions’ within the LA, thus linking them-for the first time -to specific territorial areas (Barsky et al., 2018; Grifoni and Tozzi, 2006).

In previous works, we apply the HVDM model to describe analogous evolutionary phenomenon observed in the Asian context in a similar timeframe (Barsky et al., 2018). The HVDM model serves to investigate the singularity of the human paradigm: techno-dependency– to construct a complementary vision that is useful to perceive how evolutionary change occurred through time in human techno-systems. In addition, this approach services our understanding of why culture changes and, of special importance to the late Middle Pleistocene, how similar technical developments emerged in different areas of the globe and how they diversified, leading, finally and unequivocally, to the construction of territorial identities defined by the cultural productions of the hominins occupying these lands (Barsky et al., 2018). Here, we use the HVDM model to pinpoint the basic structures of the Late Acheulian, with special reference to some well-known sites, to illustrate the major processes upon which our techno-evolutionary model is based: that of sequencing and that of bifurcation, without which the Dynamic Evolutionary Continuum (DEC) would not exist. We situate the shift from asymptotic to unbounded technical behavior in this part of the world at around 500-350 Ka; when the production of lithic tools exceeded the perfunctory, entering into a phase of intense cultural multiplicity.