The origins of the Acheulean: past and present perspectives on a major transition in human evolution

The emergence of the Acheulean from the earlier Oldowan constitutes a major transition in human evolution, the theme of this special issue. This paper discusses the evidence for the origins of the Acheulean, a cornerstone in the history of human technology, from two perspectives; firstly, a review of the history of investigations on Acheulean research is presented. This approach introduces the evolution of theories throughout the development of the discipline, and reviews the way in which cumulative knowledge led to the prevalent explanatory framework for the emergence of the Acheulean. The second part presents the current state of the art in Acheulean origins research, and reviews the hard evidence for the appearance of this technology in Africa around 1.7 Ma, and its significance for the evolutionary history of Homo erectus. This article is part of the themed issue ‘Major transitions in human evolution’

Assessing the function of pounding tools in the Early Stone Age: A microscopic approach to the analysis of percussive artefacts from Beds I and II, Olduvai Gorge (Tanzania)

This study explores the function of quartzite pounding tools from Olduvai Gorge (Tanzania) using microscopic and use wear spatial distribution analysis. A selection of pounding tools from several Bed I and II assemblages excavated by Mary Leakey (1971) were studied under low magnification (<100×), and the microscopic traces developed on their surfaces are described. Experimental data and results obtained from analysis of the archaeological material are compared in order to assess activities in which pounding tools could have been involved. Results show that experimental anvils used for meat processing, nut cracking and/or bone breaking have similar wear patterns as those observed on archaeological percussive artefacts. This is the first time that a microscopic analysis is applied to Early Stone Age pounding artefacts from Olduvai Beds I and II, and this paper highlights the importance that percussive activities played during the Early Pleistocene, suggesting a wider range of activities in addition to knapping and butchering

Thermal alterations in experimentally-flaked stone tools from Olduvai Gorge and their relevance for identification of fire in the Early Stone Age

The use of fire represents a landmark development in the technological evolution of the genus Homo. However, the earliest use and control of fire is challenging to identify in the archaeological record. Olduvai Gorge in Tanzania presents some of the best preservation and volume of sites in the Oldowan and Acheulean, but has not yet shown any clear indication of the presence of fire in lower or middle Pleistocene deposits. Through the use of visual observation and optical and scanning electron microscopy, this study identified signature features of thermal alteration in experimental stone tools of quartzite, lava and chert collected from Olduvai Gorge to establish how fire-modified rocks may potentially be identified in the archaeological record using a non-destructive methodology that can be replicated in future research

Technological behaviour in the early Acheulean of EF-HR (Olduvai Gorge, Tanzania)

Technological strategies of early humans are discussed in the light of a recently excavated stone tool assemblage from EF-HR, an archaeological site older than 1.33 Ma at Olduvai Gorge, Tanzania. Renewed fieldwork at EF-HR has unearthed a lithic collection containing over 2300 artefacts (including a hundred handaxes in stratigraphic position), which represents one of the largest assemblages for the early Acheulean in East Africa. Our technological study shows co-occurrence of two distinctive reduction sequences in the same assemblage, one aimed at obtaining small flakes and the other focused on the production of large, thick, heavy flakes that were then used as blanks for handaxe shaping. Flaking of small cores is expedient and low intensity, and knapping methods are similar to those observed in earlier Oldowan assemblages. Large Cutting Tools (LCTs) show no evidence of planform and biconvex symmetry, and shaping sequences are brief and discontinuous, indicating short use-lives for handaxes. Bifaces are rare and atypical. Recurrent morphotypes are knives, which are poorly-shaped, scraper-like, large-sized handaxes. Despite the apparent expediency of EF-HR handaxe production, a closer inspection of the interplay between debitage and façonnage stages reveals remarkably standardized procedural patterns. Large Cutting Tool blanks were produced following fixed knapping rules resulting in flakes with a specific morphology and mass distribution. Adapted to the idiosyncrasies of each blank, shaping was almost invariably imposed over the same areas in all LCTs and sought to produce morphotypes that, technologically, are remarkably identical to each other. This strongly supports the existence of mental templates and technical rules that were systematically practiced in LCT production at EF-HR, and underscore the structured nature of technological behaviour at the onset of the Acheulean in East Africa

Sr isotope stratigraphy across the Paasivaara PGE reef of the Penikat intrusion, Northern Finland:insights into the genesis of reef-type PGE mineralization

Abstract. Layered mafic-ultramafic intrusions host the largest reserves of feasible PGE commodities. Worldwide rare in the geological record, these deposits are well-constrained in a few large igneous provinces. Despite extensive research on layered intrusions and related PGE ores, the models regarding the PGE ore-formation are diverse, involving both magmatic and hydrothermal processes, and the subject remains largely debatable. In Europe, research efforts around the Baltic Large Igneous Province (BLIP) has doubled due to the new geopolitical strategy of the European Union in their search for new sources of critical metals. Global politics have placed Finnish mafic-ultramafic layered intrusions in the spotlight. Penikat is a Paleoproterozoic 2.44 Ga layered intrusion part of the east-west trending Tornio-Näränkävaara belt in northern Finland. The exposed intrusion is 23 km long and 1.5 km to 3.5 km on the current erosional level. Based on seismic and gravimetric data, it extends to 2.5 km deep. The intrussion is split into five westward-dipping blocks: Sompujärvi, Kilkka, Yli-Penikka, Keski-Penikka, and Ala-Penikka. Traditionally, Penikat is divided into five megacyclic units (MCU I-MCU V), hosting three main PGE reef horizons: the Sompujärvi Reef (SJ), located to the basal part of MCU IV; the Ala-Penikka Reef (AP), occurring within the lower proportion of unit IV; and the Paasivaara Reef (PV), which defines the hanging wall contact from the MCU IV to the MCU V. The present study comprises 700 m of stratigraphy in the Ala-Penikka block and focuses on the Paasivaara reef (PV). This platinum-enriched reef appears at the Transition Zone (TZ), along the MCU IV-V boundary. To gain new insight into Penikat’s petrogenesis, we utilize fourteen thick section samples from historic drill cores, both intersecting the PV reef, and two additional samples made after hand specimens. The sections were reviewed using petrologic microscopy before subjecting them to geochemical analyses. From these sections, we obtained new in-situ Sr isotope data in plagioclase grains by using the LA-MC-ICP-MS laser ablation technique at the GTK facilities in Espoo, Finland. The procedure can track sub-grain scale heterogeneities from core to rim. As radiogenic ratios are rarely affected by melting or crystallization, subgrain analyses are a powerful tool for tracing the contributors in a magmatic system. In addition, EPMA was used to analyze the plagioclase composition, with dedicated attention to the anorthite content in the assayed grains, at the University of Oulu, Finland. The anorthite content analysis was then compared to the LA-MC-ICP-MS results to assess the magmatic differentiation undergone by the plagioclase crystals. The results support crystallization stability in most of MCU IV (Sr(i) ~ 0.7027 ± 0.0005) and MCU V (Sr(i) 0.7032 ± 0.0005 ). Nonetheless, data record a systematic, gradual increase in radiogenic Sr signature in the sparsely 38 m between MCU IV and V. In addition, rim to core distributions register more than a single Sr(i) signature at a subgrain scale in TZ samples. The variability in the Sr signature at the Transition Zone converges with a sharp An86 content spike at the PV reef boundary, arguing for a primitive magma contributor. The results confirm affinity between the SHMB type magma, related to plume magmatism, and the parental magma of Penikat. The Transition Zone would be a product of binary and asymmetric magma mixing, each with contrasting isotopic lineages and varying degrees of crustal contamination. The discussion supports magma ascension from a staging chamber as a likely origin of the PV reef, thus supporting the new magma pulse hypothesis. Finally, the present study is compared with previous Sr(i) stratigraphy in Bushveld, showing similarities between the UPZ-MZ transition and the Transition Zone in Penikat. The detection of similar Sr(i) may lead to new PGE discoveries in the future

Oldowan technological behaviour at HWK EE (Olduvai Gorge, Tanzania)

HWK EE (Olduvai Gorge, Tanzania) is a late Oldowan site dated to ∼1.7 Ma that contains a large fossil and lithic assemblage. This paper reports on the technology of the recently excavated stone tool collection, over 18,000 pieces. Our results indicate that reduction sequences were generally short, flaking productivity was low, and knapping methods were largely simple and expedient, lacking the technical skills observed in other Oldowan assemblages. Conspicuous differences are observed in the chaînes opératoires of the three main raw materials used at HWK EE: the quartzite reduction sequence can be reconstructed in full at the site, most of the lava detached pieces are missing, and there is a preferential use of chert for retouched tools. This portrays a composite picture, where knapping expediency and low productivity are accompanied by raw material selectivity and consistent presence of retouched artefacts. Coexistence of these features in the same assemblage leads us to question the monolithic structure of the Oldowan techno-complex, and highlights the kaleidoscopic nature of technological strategies at Olduvai immediately before the earliest Acheulean handaxes appear in the sequence

Searching for the emergence of stone tool making in eastern Africa

Modern humans rely entirely on technology for their subsistence, and the interaction between technological and biological adaptations has played a key role in the evolution of our lineage. When exactly technology emerged in the fossil record and thus started to shape primate evolution has appealed to researchers since the beginnings of paleoanthropology as a discipline and, as Braun et al. (1) show in PNAS, is still today a source of important discoveries.I.d.l.T.’s research was supported by the European Research Council (Starting Grant 283366)Peer reviewe