Buccal-dental microwear depends on the abrasive content of chewed foodstuffs and can reveal long-term dietary trends in human populations. However, in vivo experimental analyses of buccal microwear formation processes are scarce. Here, we report the effects of an abrasive diet on microwear rates in two adult volunteers at intervals of 8 days over a period of 1 month and document long-term turnover over 5 consecutive years in the same subjects under an ad libitum Mediterranean diet. Buccal microwear was analyzed on mandibular first molars using high-resolution replicas and scanning electron microscopy. Microwear turnover was assessed by recording the scratches lost and gained at each time point. Our results indicate that scratch formation on enamel surfaces increased with a highly abrasive diet compared to both pre-test and post-test ad libitum dietary controls. In the long-term analysis, scratch turnover was higher than expected, but no significant long-term trends in microwear density or length were observed, because microwear formation was compensated by scratch disappearance. Our results confirm that buccal microwear patterns on mandibular molars show a dynamic formation process directly related to the chewing of abrasive particles along with ingested food. In addition, the observed long-term stability of buccal microwear patterns makes them a reliable indicator of overall dietary habits.

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Tooth wear in primates is caused by aging and ecological factors. However, comparative data that would allow us to delineate the contribution of each of these factors are lacking. Here, we contrast age-dependent molar tooth wear by scoring percent of dentine exposure (PDE) in two wild African primate populations from Gabonese forest and Kenyan savanna habitats. We found that forest-dwelling mandrills exhibited significantly higher PDE with age than savanna yellow baboons. Mandrills mainly feed on large tough food items, such as hard-shell fruits, and inhabit an ecosystem with a high presence of mineral quartz. By contrast, baboons consume large amounts of exogenous grit that adheres to underground storage organs but the proportion of quartz in the soils where baboons live is low. Our results support the hypothesis that not only age but also physical food properties and soil composition, particularly quartz richness, are factors that significantly impact tooth wear. We further propose that the accelerated dental wear in mandrills resulting in flatter molars with old age may represent an adaptation to process hard food items present in their environment.

Pygmy hunter-gatherers from Central Africa have shared a network of socioeconomic interactions with non-Pygmy Bantu speakers since agropastoral lifestyle spread across sub-Saharan Africa. Ethnographic studies have reported that their diets differ in consumption of both animal proteins and starch grains. Hunted meat and gathered plant foods, especially underground storage organs (USOs), are dietary staples for pygmies. However, scarce information exists about forager–farmer interaction and the agricultural products used by pygmies. Since the effects of dietary preferences on teeth in modern and past pygmies remain unknown, we explored dietary history through quantitative analysis of buccal microwear on cheek teeth in well-documented Baka pygmies. We then determined if microwear patterns differ among other Pygmy groups (Aka, Mbuti, and Babongo) and between Bantu-speaking farmer and pastoralist populations from past centuries. The buccal dental microwear patterns of Pygmy hunter-gatherers and non-Pygmy Bantu pastoralists show lower scratch densities, indicative of diets more intensively based on nonabrasive foodstuffs, compared with Bantu farmers, who consume larger amounts of grit from stoneground foods. The Baka pygmies showed microwear patterns similar to those of ancient Aka and Mbuti, suggesting that the mechanical properties of their preferred diets have not significantly changed through time. In contrast, Babongo pygmies showed scratch densities and lengths similar to those of the farmers, consistent with sociocultural contacts and genetic factors. Our findings support that buccal microwear patterns predict dietary habits independent of ecological conditions and reflect the abrasive properties of preferred or fallback foods such as USOs, which may have contributed to the dietary specializations of ancient human populations.

Dental casting is a very common procedure for making high-quality replicas of paleo-anthropological remains. Replicas are frequently used, instead of original remains, to study both fossil and extant Primate teeth in morphological and metrical analyses. Several commercial products can be used in molds. This study analyzed SEM image resolution and enamel surface feature definition of tooth molds at various magnification levels and obtained, with both Coltène and 3M low-viscosity body polyvinylsiloxane impression, materials and polyurethane casts. Results, through comparison with the original teeth, show that both the negative molds and the positive casts are highly reliable in replicating enamel surfaces. However, positive cast quality is optimal for SEM observation only till the fourth consecutive replica from the original mold, especially at high SEM magnification levels.

Dental microwear, usually analyzed using scanning electron microscopy (SEM) techniques, is a good indicator of the abrasive potential of past human population diets. Scanning electron microscopy secondary electrons provide excellent images of dental enamel relief for characterizing striation density, average length, and orientation. However, methodological standardization is required for interobserver comparisons since semiautomatic counting procedures are still used for micrograph characterization. The analysis of normally distributed variables allows the characterization of small interpopulation differences. However, the interobserver error rates associated with SEM experience and the degree of expertise in measuring striations are critical to population dietary interpretation. The interobserver comparisons made here clearly indicate that the precision of SEM buccal microwear measurements depends heavily on variable definition and the researcher's expertise. Moreover, error rates are not the only concern for dental microwear research. Low error rates do not guarantee that all researchers are measuring the same magnitudes of the variables considered. The results obtained show that researchers tend to maintain high intrapopulation homogeneity and low measurement error rates, whereas significant interobserver differences appear. Such differences are due to a differential interpretation of SEM microwear features and variable definitions that require detailed and precise agreement among researchers. The substitution of semiautomatic with fully automated procedures will completely avoid interobserver error rate differences.

Odontometric patterns and the degree of sexual dimorphism in dental size differ among Central African groups, indicating adaptation to their different forager and farmer lifestyles. In particular, the admixture of Bantu-speakers in Baka populations is smaller than that in other western Pygmy groups. The greater dental phenetic diversity in Baka compared to that of the smaller-toothed farmers suggests that ecogenetic and microevolutionary factors are influencing a particular divergence scenario.

Ancient DNA traces the history of hepatitis B Hepatitis B virus (HBV) infections represent a worldwide human health concern. To study the history of this pathogen, Kocher et al . identified 137 human remains with detectable levels of virus dating between 400 and 10,000 years ago. Sequencing and analyses of these ancient viruses suggested a common ancestor between 12,000 and 20,000 years ago. There is no evidence indicating that HBV was present in the earliest humans as they spread out of Africa; however, HBV was likely present in human populations before farming. Furthermore, the virus was present in the Americas by about 9000 years ago, representing a lineage sister to the viral strains found in Eurasia that diverged about 20,000 years ago. —LMZ