Patrick Schmidt

Birch tar, an adhesive made from birch trees, was the first synthetic substance made by early humans. Its manufacture and use has provided important insights into the technological and cognitive skills of past humans. So far, research has focused on the use of bark as the raw material for birch tar. However, in a different context in southern Africa, adhesives were made from leaves. There, the foragers of the Middle and Later Stone Age produced biomass tar by burning the leaves of a variety of plants using a condensation process. This raises an obvious question: is it also possible to make birch tar from leaves? This study aims at answering this question and, if the answer is yes, investigate the production parameters and chemical composition of birch leaf tars. For this, we made tar from birch leaves and bark using the condensation method, maintaining experimental parameters as similar as possible. Experimental tars were analysed using gas chromatography-mass spectrometry and infrared spectroscopy to evaluate their chemical and molecular compositions. Tar could be produced from birch leaves, but yielded less than half as much tar per gram as bark. Leaf- and bark- derived tars share several chemical characteristics but can be distinguished analytically. Our findings expand the range of potential raw materials exploited for tar production and provide new criteria for the identification and interpretation of birch tar residues in archaeological contexts.

The raw materials people used for making stone tools may contain information about their territory, exchange routs or the selection criteria they employed during provisioning. In this study, we measure the mechanical properties of different tool-stones used by foragers living during the Middle Stone Age at Sibhudu Cave in South Africa. The site yielded a long and continuous sequence that saw transitions between different raw materials and tool forms. We evaluate the quality of these different stones for tool making and use, attempting to find correlations between selected raw materials and the tools made from them. We find that the raw materials used at Sibhudu have substantially different qualities, some being easy to flake but weak upon use, some being tough during stone knapping and resistant during use. Comparing these data with the appearance and disappearance of tool types throughout the Sibhudu sequence, we note that tool-stones requiring lower flaking forces were more often retouched than those requiring great forces. Elongated products, blades, were mostly made from materials with better fracture predictability, suggesting an understanding of the basic requirements for standardising the tool knapping process. Use-related qualities, such as resistance to dulling, appear to have been of lesser importance at Sibhudu. Our results suggest that the site’s occupants had a good understanding of the qualities of rocks for specific knapping processes.

This study investigates the mechanical characteristics of lithic raw materials used during the Paleolithic in the Japanese Archipelago, focusing on Wada‐toge obsidian, Happusan andesite, and shale from the Akaya Formation. Although these sources have been well documented, few studies have examined their mechanical behavior. To evaluate the knapping quality (or fracture predictability), we measured several mechanical indicators on geological samples. Comparisons with Paleolithic assemblages suggest that the distinct mechanical signatures may have constrained prehistoric knapping strategies and influenced lithic artifact morphology. These findings highlight the mechanical property measurement for understanding prehistoric resource procurement and technological behavior in the Japanese Archipelago.

The layered semimetal WTe ₂ undergoes reversible halogen intercalation to give modulated WTe2I and multistage WTe ₂ Br _x with room-temperature “breathing” behavior.

A new niobium oxide cluster compound, Li ₃ Nb ₇ O ₅ I ₁₄ (NbI ₆ ), is presented, based on the [Nb ₇ O ₅ ] core. It competes with Li ₃ Nb ₇ O ₅ I ₁₅ in the reaction of NbI ₄ with Li ₂ O and Li ₂ (CN ₂ ) and contains (NbI ₆ ) ⁻ units inside the channels of the structure.

We identify the oldest known example of systematic heat treatment of chert in the world. The specimens come from the base of one of Australia’s oldest archaeological sequences, Nauwalabila I, in Arnhem Land, which is dated to at least 45–40 ka and probably older than 55 ka. The presence of this heat-based transformative technology in Australia has significance for reconstructions of technological evolution. One possibility is that chert heat treatment in Australia was an independent innovation. The early Australian practice of chert heat treatment is almost twice as old as is known anywhere in Eurasia, and if this developed independently in multiple places, the Australian antiquity need not be an indication of the antiquity of innovations in other regions. The difficulty with this interpretation is that chert is technically challenging to transform, creating a large innovation gap if more simple heat treatment technologies are not already in place. An alternative model is that groups of H. sapiens dispersing from Africa/West Asia possessed knowledge of stone heat treatment. Heat treatment may have spread to Australia, through South Asia and Southeast Asia, as dispersing groups continued existing practices of chert heat treatment, revealing maintenance and transmission of complex technological knowledge throughout the initial eastward spread of humans. If heat-treating knowledge persisted in the long-term, it is likely that chert treatment evolved through transference/modification of knowledge from different rock materials, such as silcrete, a material with wider thermal tolerances and more suited to the spontaneous discovery of heat treatment knowledge. This is the case in Africa, where silcrete heat treatment long predates chert treatment. However, in Australia, no silcrete treatment is evident prior to this early chert heat treatment. Silcrete at Madjedbebe, a contemporaneous site near Nauwalabila, was not heat-treated. If the transfer of heat treatment practices from silcrete (or similar rocks) to chert was a typical step in the evolution of this kind of technology, the early Australian assemblages we report here set a minimum age for this reconfiguration of thermal technology.

Adhesives are among the most informative archaeological artefacts for understanding the behaviour of Stone Age forages. In the southern African Middle and Later Stone Age, the botanical origin of most adhesives was identified as conifers of the genus Podocarpus . One of these identifications of Podocarpus adhesives comes from Elands Bay Cave. However, it has recently been shown that similar adhesives can be, and were, produced from many plants available on the southern African subcontinent, opening important questions about the role of Podocarpus within these plants. Here, we re-investigate the Elands Bay Cave adhesive record and compare it to natural and experimentally produced adhesive substances, using infrared spectroscopy and mass spectrometry. We find that Elands Bay Cave artefacts were made from the leaves of several plant species including Podocarpus spp using the condensation method. We also identify the oldest archaeological record for an adhesive based on water-soluble plant gum. These findings have important implications for our understanding of Stone Age adhesives as proxies for human evolution and the dynamics of invention.

The manufacture of limestone beads using so-called Dickenbännli drills has been proposed to be part of a large-scale societal development: specialization of labor and the resulting emergence of social stratification. These small lithic drills are abundant at many Middle and Late Neolithic sites in Southern Germany and Northern Switzerland, frequently co-occurring with limestone beads. However, the use of the drills for bead manufacture is mostly assumed rather than demonstrated. Furthermore, there is little experimental, technological and traceological evidence to support the hypothesis of a specialized production, except for the site of Hornstaad-Hörnle, where the argument is based on spatial distribution and manufacturing skill. The Late Neolithic assemblage of Kohlhau-Abri, which includes both drills and disc bead fragments, serves as a case study to reconstruct the manufacturing process of drills and limestone beads and evaluate their interconnection, ultimately examining the technical skills involved. This was achieved through explorative and controlled experiments, coupled with traceological and residue analysis of both drills and beads. Our use wear results show that the drills were used, likely to work limestone. Raman spectroscopy of a white residue found at the tip of one of the drills indicates calcite, the primary component of limestone. Neither the experimental nor the archaeological evidence suggests a necessity for specialists in bead manufacturing. Our study highlights how the application of multiple analytical approaches can provide us with complementary lines of evidence, and how such a holistic approach enables us to tackle not only small-scale but also large-scale questions.

We explore the cationic intercalation of tungsten ditelluride (WTe ₂ ) with potassium (K), rubidium (Rb), and cesium (Cs), yielding intercalation compounds of the form A _0.5 WTe ₂ ( A = K, Rb, Cs).