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Two ring-like structures made of low walls of broken stalagmite pieces, deep in a cave in France, are described and dated to around 176,000 years ago, suggesting human-made construction within the period of early Neanderthals, although the function of the structures remains conjectural. Ancient ring structures built by Neanderthals Very little is known of the cultural life of Neanderthals, the extinct hominins most closely related to modern humans, and of the earliest Neanderthals we know next to nothing. Since its natural closing during the Pleistocene period and until its discovery in 1990, no humans entered Bruniquel Cave, located in southwest France. Now Jacques Jaubert and colleagues describe and date two ring-like structures made of low walls of broken stalagmite pieces, deep in Bruniquel Cave. The construction of the structures 336 metres from the cave entrance, the larger more than five metres across, speaks of human industry, and the date of around 176,000 years ago places it within the compass of early Neanderthals and among the earliest well-dated structures made by humans. Traces of burning are found associated with the stalagmites, but the function of these structures remains conjectural. Very little is known about Neanderthal cultures 1 , particularly early ones. Other than lithic implements and exceptional bone tools 2 , very few artefacts have been preserved. While those that do remain include red and black pigments 3 and burial sites 4 , these indications of modernity are extremely sparse and few have been precisely dated, thus greatly limiting our knowledge of these predecessors of modern humans 5 . Here we report the dating of annular constructions made of broken stalagmites found deep in Bruniquel Cave in southwest France. The regular geometry of the stalagmite circles, the arrangement of broken stalagmites and several traces of fire demonstrate the anthropogenic origin of these constructions. Uranium-series dating of stalagmite regrowths on the structures and on burnt bone, combined with the dating of stalagmite tips in the structures, give a reliable and replicated age of 176.5 thousand years (±2.1 thousand years), making these edifices among the oldest known well-dated constructions made by humans. Their presence at 336 metres from the entrance of the cave indicates that humans from this period had already mastered the underground environment, which can be considered a major step in human modernity.

Spring water geochemistry is applied here to evaluate the geothermal potential in Rhenohercynian fold and thrust belt around the deepest borehole in Belgium (Havelange borehole: 5648 m MD). Fifty springs and (few) wells around Havelange borehole were chosen according to a multicriteria approach including the hydrothermal source of “Chaudfontaine” (T ≈ 36 °C) taken as a reference for the area. The waters sampled, except Chaudfontaine present an in-situ T range of 3.66–14.04 °C (mean 9.83 °C) and a TDS (dry residue) salinity range of 46–498 mg/L. The processing methods applied to the results are: hierarchical clustering, Piper and Stiff diagrams, TIS, heat map, boxplots, and geothermometry. Seven clusters are found and allow us to define three main water types. The first type, locally called “pouhon”, is rich in Fe and Mn. The second type contains an interesting concentration of the geothermal indicators: Li, Sr, Rb. Chaudfontaine and Moressée (≈5 km East from the borehole) belong to this group. This last locality is identified as a geothermal target for further investigations. The third group represents superficial waters with frequently high NO3 concentration. The application of conventional geothermometers in this context indicates very different reservoir temperatures. The field of applications of these geothermometers need to be review in these geological conditions.

Despite uncontested evidence for fossils belonging to the early hominin genus Australopithecus in East Africa from at least 4.2 million years ago (Ma), and from Chad by 3.5 Ma, thus far there has been no convincing evidence of Australopithecus, Paranthropus or early Homo from the western (Albertine) branch of the Rift Valley. Here we report the discovery of an isolated upper molar (#Ish25) from the Western Rift Valley site of Ishango in Central Africa in a derived context, overlying beds dated to between ca. 2.6 to 2.0 Ma. We used µCT imaging to compare its external and internal macro-morphology to upper molars of australopiths, and fossil and recent Homo. We show that the size and shape of the enamel-dentine junction (EDJ) surface discriminate between Plio-Pleistocene and post-Lower Pleistocene hominins, and that the Ishango molar clusters with australopiths and early Homo from East and southern Africa. A reassessment of the archaeological context of the specimen is consistent with the morphological evidence and suggest that early hominins were occupying this region by at least 2 Ma.

Two ring-like structures made of low walls of broken stalagmite pieces, deep in a cave in France, are described and dated to around 176,000 years ago, suggesting human-made construction within the period of early Neanderthals, although the function of the structures remains conjectural.