Adeline Le Cabec’s research while affiliated with University of Bordeaux and other places

The “teeth-as-tools” hypothesis posits that Neanderthals used their anterior teeth as a tool or a third hand for non-dietary purposes. These non- or para-masticatory activities (e.g., tool-making or food preparation prior to ingestion) have also been described in other past and extant human populations, and other Primates. Cementum is the mineralized tissue that covers the tooth root surface and anchors it to the alveolar bone. Under certain conditions (e.g., mechanical stress, infection), its production becomes excessive (i.e., beyond the physiological state) and is called ‘hypercementosis’. Several studies in dental anthropology have established a correlation between the teeth-as-tools and hypercementosis. The present work aims to characterize the different patterns of cementum apposition on archeological teeth and discuss their supposed etiology. Using microtomography and confocal microscopy, the patterns of cementum apposition (i.e., thickness, location, and surface characteristics) were analyzed in 35 hypercementotic teeth (Sains-en-Gohelle, France; 7th–17th c. A.D.). Four groups were identified with distinct hypercementosis patterns: (1) impacted, (2) infected, (3) hypofunctional, and (4) hyperfunctional teeth. Characterizing hypercementosis can contribute to documenting the oral health status (paleopathology) and/or masticatory activity of individuals, even from isolated teeth. This has implications for the study of fossil hominins, particularly Neanderthals, known for their use of anterior teeth as tools and frequent and substantial occurrence of hypercementosis.

Zinc is incorporated into enamel, dentine and cementum during tooth growth. This work aimed to distinguish between the processes underlying Zn incorporation and Zn distribution. These include different mineralisation processes, the physiological events around birth, Zn ingestion with diet, exposure to the oral environment during life and diagenetic changes to fossil teeth post-mortem. Synchrotron X-ray Fluorescence (SXRF) was used to map zinc distribution across longitudinal polished ground sections of both deciduous and permanent modern human, great ape and fossil hominoid teeth. Higher resolution fluorescence intensity maps were used to image Zn in surface enamel, secondary dentine and cementum, and at the neonatal line (NNL) and enamel–dentine–junction (EDJ) in deciduous teeth. Secondary dentine was consistently Zn-rich, but the highest concentrations of Zn (range 197–1743 ppm) were found in cuspal, mid-lateral and cervical surface enamel and were similar in unerupted teeth never exposed to the oral environment. Zinc was identified at the NNL and EDJ in both modern and fossil deciduous teeth. In fossil specimens, diagenetic changes were identified in various trace element distributions but only demineralisation appeared to markedly alter Zn distribution. Zinc appears to be tenacious and stable in fossil tooth tissues, especially in enamel, over millions of years.

In Africa, the scarcity of hominin remains found in direct association with stone tools has hindered attempts to link Homo habilis and Homo erectus with particular lithic industries. The infant mandible discovered in level E at Garba IV (Melka Kunture) on the highlands of Ethiopia is critical to this issue due to its direct association with an Oldowan lithic industry. Here we use synchrotron imaging to examine the internal morphology of the unerupted permanent dentition and confirm its identification as Homo erectus. Additionally, we utilize new palaeomagnetic ages to show that 1) the mandible in level E is ca. 2 million-years-old, and represents one of the earliest Homo erectus fossils, and 2) that overlying level D, ca. 1.95 million-years-old, contains the earliest known Acheulean assemblage.

El Castillo cave is a well-known site because of its Paleolithic archaeology and parietal rock art. This paper is focused on the human remains found by V. Cabrera in the Mousterian Unit XX assigned to MIS 4 and early MIS 3. The fossils consist of one upper left second premolar (ULP4), one incomplete proximal hand phalanx, and one partial femoral head. The tooth and the phalanx were assigned to adults, whereas the femoral head belonged to an immature individual due to the absence of fusion traces to the metaphyseal surface. The external morphology and metrical characterization of the Castillo-1466 (ULP4) tooth crown was quantified and compared to the variability of other Neanderthal dental remains and a sample of modern human populations. We also quantified its 3D enamel thickness distribution, its roots morphology, as well as the presence of chipping, and their possible relation to masticatory or paramasticatory activities. Castillo-1466 shows crown dimensions compatible with middle-sized Neanderthal teeth, but with a remarkably thicker enamel than other Neanderthal premolars, such as Marillac 13. The femoral head and the hand phalanx fragment are compared to published values for Neanderthals, although both partial fossils lack diagnostic features precluding any clear taxonomic diagnostic. Therefore, their attribution to Neanderthals is assumed based on the dating of the layers in which they were discovered. El Castillo cave Mousterian fossils represent another contribution to the knowledge of the Middle Paleolithic populations of Northern Spain, where different sites along the Cantabrian mountains yielded several human remains assigned to MIS 4 and early MIS 3.