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The microlithic component in Eurasian Pleistocene stone tool assemblages has been identified as a relevant part of technological behaviours just recently. Traditionally the small component of pre-sapiens lithic assemblages was systematically classified into the category of “knapping waste/debris”. These tools are usually unretouched, so not easily identifiable as searched tools according to traditional criteria in lithic morpho-technical studies and, as a result, assumed not to be informative about past human behaviours. The first works that allowed archaeologists to identify tiny lithic items as tools by ancient hominins were mainly focused on use-wear analysis (recognising that they were used in meat-cutting activities since Lower Palaeolithic, Barkai et al., 2010), and refitting (showing a flexible character of Middle Palaeolithic stone tool production, systematically fragmented in the spatial, temporal, and social domains, Turq et al. 2013). Reanalysis of Eurasian assemblages was favoured by the identification of small implements in the African records (ESA, MSA, and LSA). Furthermore, micro-artefacts have been showed to be more frequently attested in their original location of use and in primary activity areas being charged of a special value for archaeologists when it comes to identifying and interpreting cultural aspects looking at the spatial distribution in hunter-gatherers’ campsites (Hull, 1987). In the last decade several papers have showed the widespread production of small items that are currently known as a basic component of Middle Palaeolithic technology (e.g., Borel at al., 2017 ; Romagnoli et al., 2022). However, these studies also clearly showed that, in some cases, these small tools were part of the transported toolkit. Thus, they can be related to a huge diversity of economic and mobility strategies. These include anticipated task planning, in-situ expedient production of effective cutting edges, exploitation of lower quality resources, or different manufacture procedures. Still, microlithisation of core knapping, exploitation of core-on-flake, bipolar production, recycling, etc. and the multiplicity of behaviours related to them are not necessarily mutually exclusive. While the issue of microliths in Middle Palaeolithic is currently a cutting edge in human evolution studies, it is still looked through a blurry lens because of the lack of clear definitions. One problem concerns the length or weight threshold that small items should have and the use of the generic label “microstuff” that impede to understand the specific contribution of these productions as cultural component in regional groups. Another problem concerns their role in hominins daily lifeways at different temporal and spatial scales of analysis, their possible integration in the technological and social organisation of the human groups. In this presentation we briefly consider these problems through some archaeological examples on which we are working. They converge on showing this variability within micro-productions studies in Middle Palaeolithic and current limitations to their understanding. We also discuss some proprietary aspects in relation to taxonomy and technology, as well as possible pathways to further investigate this issue. This paper is a first step to build a collective, collaborative project to investigate Middle Palaeolithic microproduction with a more focused look.

Backed flakes (core edge flakes and pseudo-Levallois points) represent special products of Middle Paleolithic centripetal flaking strategies. Their peculiarities are due to their roles as both a technological objective and in the management of core convexities to retain its geometric properties during reduction. In Middle Paleolithic contexts, these backed implements are commonly produced during Levallois and discoidal reduction sequences. Backed products from Levallois and discoidal reduction sequences often show common geometric and morphological features that complicate their attribution to one of these methods. This study examines the identification of experimentally produced discoidal and recurrent centripetal Levallois backed products (including all stages of reduction) based on their morphological features. 3D geometric morphometrics are employed to quantify morphological variability among the experimental sample. Dimensionality reduction though principal component analysis is combined with 11 machine learning models for the identification of knapping methods. A supported vector machine with polynomial kernel has been identified as the best model (with a general accuracy of 0.76 and an area under the curve [AUC] of 0.8). This indicates that combining geometric morphometrics, principal component analysis, and machine learning models succeeds in capturing the morphological differences of backed products according to the knapping method, This research has been supported by the project SI1/PJI/2019-00488 funded by Comunidad Autonoma de Madrid and Universidad Autonoma de Madrid. FR research studies are also supported by the project ID2019-103987GBC33 funded by the Spanish Ministry of Science and Innovation

Quartär – Internationales Jahrbuch zur Erforschung des Eiszeitalters und der Steinzeit, Bd. 63 (2016): Quartär. Internationales Jahrbuch zur Eiszeitalter- und Steinzeitforschung

Le niveau M et le sous-niveau Oa du site de l’Abric Romaní (Capellades, Barcelona, Espagne), présentent différents types de contextes technologiques. Les chaînes opératoires du niveau M montrent des stratégies expéditives. L’assemblage lithique du sous-niveau Oa est associé à des stratégies hiérarchisées et à des chaînes opératoires Levallois. Le silex est la roche plus utilisée (80,8 % pour le niveau M, 91,6 % pour le niveau Oa). Toutes les formations géologiques contenant du silex sont localisées dans un rayon de 30 kilomètres, les plus nombreuses étant les formations évaporitiques des marges de la dépression de l’Èbre. Le type de silex le plus représenté dans les deux niveaux provient d’un gisement situé à environ 16 kilomètres au nord-ouest du site. Ces rayons d’approvisionnements, identiques pour des systèmes techniques aussi différents, nous incitent à proposer l’hypothèse que les choix de matières premières sont majoritairement liés à des facteurs socio-économiques, et non uniquement à des aspects purement technologiques. Level M and sub-level Oa at Abric Romaní (Capellades, Barcelona, Spain) are showing various types of technological contexts. The chaines opératoires of level M show expedient strategies. The lithic assemblage of sub-level Oa is associated to hierarchized strategies and Levallois chaines opératoires. Chert is the most used rock (level M = 80.8%; level Oa = 91.6%). All geological formation containing chert are located in a 30 km radius, the most numerous being the evaporite formations of the margins of the Ebro depression. The chert type most commonly found in both level is located about 16 km to the NW of the site. These identical supply distances for such different technological systems encourage us to consider that the raw material choices are mostly connected to socio-economic factors and not solely to technological aspects.