Search Results (2)

Litter size plays an essential role in mammalian evolution and is one of the most important factors determining whether an organism is deemed to have a ‘slow’ or ‘fast’ life history strategy. Humans are distinct in being classified as having slow life history yet bearing singletons who have completed relatively less growth than other ape neonates. Previous work has proposed that the ancestral primate gave birth to singletons. However, primate litter size has not yet been contextualized within a broad phylogenetic assessment of mammalian life history. We performed a comprehensive investigation of primate litter size using life history data for 155 primate species, and litter size data for an additional 791 boreoeutherian mammals. Litter size and life history traits have strong phylogenetic signal in primates (Pagel’s lambda: 0.99, p < 0.001; Blomberg’s K: 0.6311. p < 0.001), and litter size is significantly negatively correlated with gestation length (p < 0.001). Our data support that the last common ancestors of both primates and Haplorhini gave birth to multiples (litter size 1.7 and 1.6, respectively). We also find that singleton-bearing pregnancies evolved convergently in multiple primate lineages, including tarsiers and other haplorhines. This study contributes significantly to our understanding of life history and litter size in mammals, and we emphasize the utility of a callitrichid model for investigating the evolution of human reproduction. Full article

A monkey phantom is of significant value for electromagnetic radiation (EMR) dosimetry simulations. Furthermore, phantoms in various postures are needed because living beings are exposed to EMR in various postures during their daily routine. In this study, we attempted to produce monkey phantoms based on three daily postures of a rhesus monkey. From our Visible Monkey project, we selected surface models with 177 monkey structures. In the surface models, 52 virtual joints were created to allow for changes from the anatomical position to quadrupedal and sitting positions using commercial software. The surface models of the three positions were converted into monkey voxel phantoms. These phantoms were arranged in three positions, and the number of voxels and mass of each structure were analyzed. The phantoms in anatomical, quadrupedal, and sitting positions have a total of 5,054,022, 5,174,453, and 4,803,886 voxels, respectively. The mass of 177 structures in three positions were also calculated based on the number of voxels. By comparing the monkey phantom with the phantom of a female human, we confirmed thicker skin, less fat, heavier muscle, and a lighter skeleton in monkeys than those in humans. Through posture-transformed monkey phantoms, more precise EMR simulations could be possible. The ultimate purpose of this study is to determine the effects of EMR on humans. For this purpose, we will create posture-transformed human phantoms in a following study using the techniques employed herein and the human phantoms from our previous study. Full article