Extant primates, including humans, exhibit diverse morphotypes (defined here by body mass distribution and segment lengths) that reflect their locomotor adaptations. Reconstructing the evolutionary history of primates requires to understand the morphological shifts, yet the morphotypes of extinct species are often only partially inferred from fragmentary fossil remains. Such limitation typically impedes the use of quantitative methods, which require near-complete skeletal data to estimate segmental inertial properties. To address this challenge, we developed a novel methodological framework using extant primate species to estimate theoretical ancestral morphotypes and their diversity across the primate phylogenetic tree. Our approach integrates a unique dataset of morphometric measurements collected over the past decades from anaesthetized primates in collaboration with multiple institutions (e.g., zoological park of Besançon, zoological and botanical park of Mulhouse, primatology station of the CNRS). Using a validated geometric model (Crompton et al., 1996), we reconstructed the morphotypes of 124 individuals coming from 23 species. This dataset, combined with a bootstrap resampling method, defines a "polymorphospace" of extant primates, encompassing both extreme (e.g., gibbons and humans) and intermediate species (bonobos, baboons, colobus), as well as diverse inter-individual associations. This captures a broad spectrum of morphological variation. By integrating phylogenetic relationships and bootstrap resampling, we generated 1000 reconstructions of ancestral morphotypes at key nodes of the Hominidae family tree and at 1 million-year intervals along branches. Comparing these reconstructions with the limb proportions of fossil taxa (e.g. intermembral index), such as Ardipithecus ramidus, Australopithecus afarensis, Australopithecus africanus, Hispanopithecus laietanus, Homo habilis, Homo erectus and Oreopithecus bambolii, allows us to validate our model and propose plausible morphotypes for these extinct species. This analysis led us to develop MorphoBack, an open-source MATLAB application that allows users to input their own fossil data and generate ancestral morphotype reconstructions.
The West African chimpanzee is critically endangered throughout its range. The conservation of the species depends on the preservation of its habitat and on the accurate estimation of its population density, which is essential to the development of an appropriate management plan. Thus we monitored 136 chimpanzee nests in Fongoli (southeastern Senegal) between June 2022 and January 2024 in order to determine the plant species preferentially used for their construction, the main nesting habitats and the nest decay rate. This study reveals that chimpanzees in Fongoli mainly use Pterocarpus eurinaceus to build their nests. The different types of habitat in the study area are used periodically for nesting, with a marked preference for woodland savannas. Average nest height is7.2 ± 0.56 m, slightly lower than at other chimpanzee study sites in Senegal. The average lifespan of chimpanzee nests is 48.6 ± 2.2 days, and the rate of degradation depends on the season of construction, the physical characteristics of the nest trees and the types of habitat in which the nests are built. This research highlights the plant species and habitats essential to chimpanzee survival in Senegal. It also highlights the need for researchers to use site-specific nest decay rates to estimate ape population size.
