Flavio De Angelis, Anna Russo, Antonio Nappo
et al.
Background/Objectives: This study explores the evolution and morphology of the human mandible, focusing on recent changes and adaptations over the last 2000 years. It aims to examine how functional, genetic, and environmental factors influence mandibular size, shape, and sexual dimorphism by analyzing key anatomical landmarks—the horizontal ramus (HR), ascending ramus (AR), and mandibular angle (MA). Methods: A retrospective approach was employed using computed tomography (CT) scans of 39 mandibular samples from various historical periods, ranging from the Roman Imperial Age to the present day. Imaging was conducted using a 64-slice multislice computed tomography (MSCT) scanner, and the resulting data were processed to generate detailed 3D reconstructions for morphological assessment. Results: The analysis reveals that present-day samples exhibit significantly less variation in AR and MA compared to archaeological specimens, suggesting a trend of gracilization over time. Statistically significant differences were found in MA, likely influenced by environmental, dietary, and cultural factors. Correlation analysis showed moderate to weak relationships between AR, HR, and MA across sample groups, with significant sexual dimorphism in AR within the archaeological sample. Principal Component Analysis (PCA) further supported these findings, demonstrating a clear distinction between gracile modern mandibles and more robust ancient ones. Conclusions: These findings provide insights into the evolutionary trajectory of the human mandible, underscoring the influence of dietary and cultural shifts on mandibular structure over the past two millennia.
Zhengyi Zhang, Yulong Guo, Mingsheng Zhuang
et al.
ABSTRACT Gut microbiota of the bumblebee is critical as it modulates the health and fitness of the host. However, the mechanisms underlying the formation and maintenance of the diversity of bumblebee gut bacteria over a long period of evolution have yet to be elucidated. In particular, the gut bacterial diversity and community assembly processes of Bombus pyrosoma across the Chinese border remain unclear. In this study, we systematically carried out unprecedented sampling of 513 workers of the species Bombus pyrosoma across the Chinese landscape and used full-length 16S rRNA gene sequencing to examine their gut microbiota diversity and biogeography. The gut microbiota composition and community structure of Bombus pyrosoma from different geographical locations were diverse. On the whole, the gut bacteria Gilliamella and Snodgrassella are dominant in bumblebees, but opportunistic pathogens Serratia and Pseudomonas are dominant in some sampling sites such as Hb15, Gs1, Gs45, Qhs15, and Ssx35. All or part of environmental factors such as latitude, annual mean temperature, elevation, human footprint, population density, and annual precipitation can affect the alpha diversity and community structure of gut bacteria. Further analysis showed that the assembly and shift of bumblebee gut bacterial communities under geographical variation were mainly driven by the stochastic drift of the neutral process rather than by variable selection of niche differentiation. In conclusion, our unprecedented sampling uncovers bumblebee gut microbiome diversity and shifts over evolutionary time.IMPORTANCEThe microbiotas associated with organisms facilitates host health and fitness, and the homeostasis status of gut microbiota also reflects the habitat security faced by the host. In addition, managing gut microbiota is important to improve bumblebee health by understanding the ecological process of the gut microbiome. Thus, we first carried out an runprecedented sampling of 513 workers of the species Bombus pyrosoma across the Chinese landscape and used full-length 16S rRNA gene sequencing to uncover their gut microbiota diversity and biogeography. Our study provides new insights into the understanding of gut microbiome diversity and shifts for Chinese Bumblebee over evolutionary time.