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Author(s): Fernando V. Ramirez Rozzi (corresponding author) [1]; José Maria Bermudez de Castro [2] Life-history traits correlate closely with dental growth [1], so differences in dental growth within Homo can [...]

Reproductive seasonality is a phenomenon common to human and animal populations and driven by, among others, climatic variables. Given the currently changing climate and its impacts on both the environment and human lives, the question arises of its potential effects on reproductive seasonality. Few studies have specifically explored the seasonality of reproduction among hunter-gatherers and anyone investigated how current climate change might affect this phenomenon. In this study we addressed reproductive seasonality in the Baka Pygmy living in African rain forests. Since reproductive seasonality can be linked to weather patterns, we explore this possibility. However, climatic variables driving weather patterns have changed over the years, so we assessed whether this has influenced the Baka reproductive pattern. Based on 34 years of written birth records and oral questionnaires from 13 years of systematic fieldwork, we observed a bimodal birth pattern with two birth peaks at 6-month intervals. Our results demonstrate that precipitation at conception or at birth potentially has effects, respectively negative and positive on the monthly number of births; and temperature has a role in controlling other variables that do affect the reproductive pattern. Changing weather patterns appear to be affecting the reproductive seasonality in the Baka, suggesting that attention needs to be given to the influence of global climate change on forager societies. [ABSTRACT FROM AUTHOR]

Excess fat is a risk factor for many chronic diseases which can lead to premature mortality. Many studies have proposed predictive equations for body fat mass and body fat mass percentage based on anthropometric measures in relation to age and sex. However, the use of these predictive equations on other subject samples may not be relevant. Our objective is to assess whether the predictive equations proposed in the literature are generalizable to any population. We obtained fat mass and fat percentage on a reference population using Absorptiometry DXA. The predictive equations were applied to our population and the mean and individual differences between actual and estimated values were obtained. Predictive equations obtained from a reduced number of subjects have a very high Standard Error of Estimate (>3) and therefore their accuracy is not acceptable. Only the formulae established from a large number of individuals allow the estimation of values whose Standard Error of Estimate is less than 3. These equations, thanks to the large sample size, include a sufficiently large variability in anthropometric measurements covering the diversity of anthropometric values for the same fat value. However, predictive equations based on a large sample size, while exhibiting no current difference in variances, can show a shift in mean values. This mean-shift is the result of differences in DXA devices and needs to be corrected. It means that DXA values from a few individuals in the population under study must be obtained to calculate a corrective factor. [ABSTRACT FROM AUTHOR]

Objectives: Central African small‐scale foragers subsist primarily on hunting game activities and wild plant‐food gathering. Starch‐rich tubers are underground storage organs (USOs) and staple food resources in savanna and tropical rainforests. However, little is known about the effect of USO consumption on tooth wear development in living hunter‐gatherers. We report age‐ and sex‐dependent tooth wear rates in forest‐dwelling Baka Pygmies with well‐documented wild‐yam‐tuber‐based diet to explore the long‐term impact of USO mechanical hardness and abrasiveness on the wearing down of the teeth. Materials and Methods: Percentages of dentine exposure (PDEs) of permanent left mandibular first molars (M1) were recorded using in vivo high‐resolution replicas of Baka individuals (aged 8–33 years), inhabiting Le Bosquet district in Cameroon (Western Africa). Regression and covariance analyses were used to test the effect of individual aging by sex on PDE rates. Results: We found a strong increase of PDE by age among Baka individuals. No evidence of sexual dimorphism in wear patterns suggests similar sex‐related dietary and masticatory demands during growth. Overall, greatest dentine exposure values ≈4% denote unexpected slow wear down rates for foraging diets relying on USO consumption. Discussion: The low molar wear rates with age found in Baka Pygmies contrast with extensive wear rates in savanna‐dwelling foragers, reflecting differences in thermal processing techniques affecting fracture toughness and grittiness of mechanically challenging foods. Our findings reveal that culture‐specific dietary proclivities influence tooth wear among foraging behaviors with important implications in hominin dietary versatility and abrasive stress on chewing surfaces. [ABSTRACT FROM AUTHOR]

Background: The relationship between tooth size and stature has been analysed extensively at the interspecies level but has received less attention at the intraspecies level. The relationship between these two parameters does not seem to be the same among modern human populations. Aim: The aim of this study is to analyse the relationship between tooth dimensions and body measurements in the Baka Pygmies. Subjects and methods: Height, weight, and tooth dimensions were obtained for 45 adult Baka females and 17 males from Le Bosquet (Cameroon). Correlations were obtained between the variables and compared to results for other human populations. Results: The Baka population is distinctive in the small number of significant correlations. Only two buccolingual diameters among Baka females show any significant correlation with height. The lack of significant correlations between tooth dimensions and body dimensions among the Baka means that changes in body size are accompanied by random variations in tooth dimensions. Conclusion: The absence of correlations may be accounted for by the impact of environmental effects on the somatic growth of the Baka producing a Pygmy phenotype adapted to live in the forest. It is worth noting that many correlations become significant when sexes are pooled. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Odontometric studies of African populations show high within‐group variation in tooth size. Overall, North Africans exhibit smaller dimensions than groups from eastern and southern sub‐Saharan regions, but no previous studies have analyzed the full dental metrics among extant African Pygmy hunter‐gatherers and Bantu‐speaking farmers. Furthermore, the population variability in tooth crown sizes from equatorial rainforest regions remains to be elucidated. Materials and Methods: The mesiodistal and buccolingual diameters of the permanent teeth (I1‐M2) were measured in vivo using high‐resolution replicas from Baka Pygmies and Mvae and Yassa Bantu‐speakers from Cameroon (western Africa). Analyses of variance were used to record sex‐related and population‐level differences in tooth sizes, and a principal component analysis of geometrically scaled measures was used to plot the odontometric variability among groups. Results: Cameroonian Baka Pygmies differ in dental size from their Bantu‐speaking neighbors. Molar teeth are larger in Pygmies than in Bantu individuals, while the anterior dentition is larger in the Bantu. Baka males exhibit significantly larger teeth than females, whereas sexual dimorphism in non‐Pygmies is only present in the anterior dentition. Discussion: 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. [ABSTRACT FROM AUTHOR]

To understand the diversity of human growth and development from an evolutionary point of view, there is an urgent need to characterize the life-history variables of vanishing forager societies. The small body size of the Baka pygmies is the outcome of a low growth rate during infancy. While the ages at sexual maturity, menarche, and first delivery are similar to those in other populations, fertility aspects are unknown. In the Le Bosquet district in Cameroon, thanks to systematic birth records kept from 1980 onwards, we were able to assign ages to individuals with certainty. This study, based on chronological records and on data collected from 2007 to 2017, presents life-history variables related to fertility and mortality among the Baka pygmies: total fertility rate, age-specific fertility rate, completed family size, reproductive span, age at menopause, and infant and juvenile mortality. The Baka present low infant and juvenile mortality, and their fertility pattern differs from that of other forager societies in the higher age-specific fertility rates found in the two lower age classes. Future studies will need to assess whether this particular pattern and the short interbirth interval are related to highly cooperative childrearing, which in the Baka is associated with slow growth. The fertility rate has fallen drastically since 2011, and this matches the arrival of cheap alcohol in the community. Our data provide a first-hand record of the impact of alcohol on fertility in a hunter-gatherer society which appears to be seriously compromising the survival of the Baka. [ABSTRACT FROM AUTHOR]

Recent studies suggest that the hypodigms representing the two earliest Australopithecus ( Au. anamensis and Au. afarensis) form an ancestor-descendant lineage. Understanding the details of this possible transition is important comparative evidence for assessing the likelihood of other examples of ancestor-descendant lineages within the hominin clade. To this end we have analyzed crown and cusp base areas of high resolution replicas of the mandibular molars of Au. anamensis (Allia Bay and Kanapoi sites) and those of Au. afarensis (Hadar, Laetoli, and Maka). We found no statistically significant differences in crown areas between these hypodigms although the mean of M1 crowns was smaller in Au. anamensis, being the smallest of any Australopithecus species sampled to date. Intraspecies comparison of the areas of mesial cusps for each molar type using Wilcoxon signed rank test showed no differences for Au. anamensis. Significant differences were found between the protoconid and metaconid of Au. afarensis M2s and M3s. Furthermore, the area formed by the posterior cusps as a whole relative to the anterior cusps showed significant differences in Au. afarensis M1s and in Au. anamensis M2s but no differences were noted for M3s of either taxon. Developmental information derived from microstructural details in enamel shows that M1 crown formation in Au. anamensis is similar to Pan and shorter than in H. sapiens. Taken together, these data suggests that the overall trend in the Au. anamensis- Au. afarensis transition may have involved a moderate increase in M1 crown areas with relative expansion of distal cusps. Am J Phys Anthropol , 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Pygmy hunter-gatherers coexist in Central Africa with well-established Bantu agriculturalists and both groups differ in culture and phenotypic traits. Previous odontometric studies found that tooth dimensions for upper molars (M1-3) in Pygmies are not different to those in non-pygmies. However, dental phenotypic patterns between populations remain unclear because of the small samples sizes studied. Maximum buccolingual and mesiodistal crown diameters were recorded from high-resolution in vivo replicas of upper and lower (I1-M2) teeth in sample of Baka (n= 103; Cameroon) and Mbuti (n=29; Democratic Republic of Congo) Pygmies and, Bantu speaking individuals, Mvae (n=14) and Yassa (n=18) from Cameroon. Uni- and multivariate statistical tests were used to evaluate the differences among groups. We found that upper postcanine tooth crowns tended to be larger in Pygmies than in Bantu groups while anterior and lower teeth are shorter. The two first Principal Components obtained account for 50.1% of total variance. The highest loadings (r>0.7) in PC1 (42.93%) are all premolar and molar measurements. In contrast, PC2 (7.14%) appears to be driven by anterior dentition (I1-C) width. In addition, Canonical variate analysis showed significant between-group differences (Wilks'λp<0.0001). The two factors obtained reveal that odontometric patterns differ (ANOVA p<0.001) between Pygmies and Bantu-speaking farmers. No differences were found within Bantu populations but Baka and Mbuti Pygmies showed dissimilar patterns (Tukey's HSDp<0.001). The patterning of dental variation found is consistent with those obtained from recent genetic data where Mbuti Pygmies differ substantially from that of western Pygmies. Dental metrics are often considered less robust than morphological traits, however cross-cultural multivariate studies found significant variation in tooth size among human populations. Since tooth size appears to be strongly heritable, our preliminary odontometrics results support findings based on diversification hypothesis for Central African Pygmies. [ABSTRACT FROM AUTHOR]

The view that Aurignacian technologies and their associated symbolic manifestations represent the archaeologicalproxy for the spread of Anatomically Modern Humans into Europe, is supported by few diagnostic human remains, including those from the Aurignacian site of Les Rois in south-western France. Here we reassess the taxonomic attribution of the human remains, their cultural affiliation, and provide five new radiocarbon dates for the site. Patterns of tooth growth along with the morphological and morphometric analysis of the human remains indicate that a juvenile mandible showing cutmarks presents some Neandertal features, whereas another mandible is attributed to Anatomically Modern Humans. Reappraisal of the archaeological sequence demonstrates that human remains derive from two layers dated to 28-30 kyr BP attributed to the Aurignacian, the only cultural tradition detected at the site. Three possible explanations may account for this unexpected evidence. The first one is that the Aurignacian was exclusively produced by AMH and that the child mandible from unit A2 represents evidence for consumption or, more likely, symbolic use of a Neandertal child by Aurignacian AMH The second possible explanation is that Aurignacian technologies were produced at Les Rois by human groups bearing both AMH and Neandertal features. Human remains from Les Rois would be in this case the first evidence of a biological contact between the two human groups. The third possibility is that all human remains from Les Rois represent an AMH population with conserved plesiomorphic characters suggesting a larger variation in modern humans from the Upper Palaeolithic.