Brenda J. Bradley

Dispersed Male Networks in Western Gorillas

Although kin-selection theory has been widely used to explain the tendency of individuals to bias beneficial behaviors towards relatives living within the same social group, less attention has focused on kin-biased interactions between groups. For animal societies in which females emigrate, as is the case for mountain gorillas (Gorilla beringei beringei), encounters between males in different groups often involve aggressive displays that can escalate to physical violence and fatal injuries. However, recent findings on the little-studied western gorilla (Gorilla gorilla) indicate that interactions between social groups occur more frequently than they do in mountain gorillas and are often, although not always, surprisingly nonaggressive. We investigated the pattern of genetic relationships between individuals of different groups and found evidence suggesting a previously unrecognized dispersed male network social structure in western gorillas in which the single males leading social groups were usually related to one or more nearby males. We propose that this provides a basis for extra-group, kin-biased behaviors and may explain the reported peaceful intergroup interactions. Furthermore, these results suggest that a patrilocal social structure, in which males remain in their natal region and potentially benefit from kin associations, is a feature unifying African apes and humans.

Reconstructing phylogenies and phenotypes: a molecular view of human evolution

This review broadly summarizes how molecular biology has contributed to our understanding of human evolution. Molecular anthropology began in the 1960s with immunological comparisons indicating that African apes and humans were closely related and, indeed, shared a common ancestor as recently as 5 million years ago. Although initially dismissed, this finding has proven robust and numerous lines of molecular evidence now firmly place the human‐ape divergence at 4–8 Ma. Resolving the trichotomy among humans, chimpanzees and gorillas took a few more decades. Despite the readily apparent physical similarities shared by African apes to the exclusion of modern humans (body hair, knuckle‐walking, thin tooth enamel), the molecular support for a human–chimpanzee clade is now overwhelming. More recently, whole genome sequencing and gene mapping have shifted the focus of molecular anthropology from phylogenetic analyses to phenotypic reconstruction and functional genomics. We are starting to identify the genetic basis of the morphological, physiological and behavioural traits that distinguish modern humans from apes and apes from other primates. Most notably, recent comparative genomic analyses strongly indicate that the marked differences between modern humans and chimpanzees are likely due more to changes in gene regulation than to modifications of the genes themselves, an idea first proposed over 30 years ago. Almost weekly, press releases describe newly identified genes and regulatory elements that seem to have undergone strong positive selection along the human lineage. Loci involved in speech (e.g. FOXP2), brain development (e.g. ASPM), and skull musculature (e.g. MYH16) have been of particular interest, but some surprising candidate loci (e.g. those involved in auditory capabilities) have emerged as well. Exciting new research avenues, such as the Neanderthal Genome Project, promise that molecular analyses will continue to provide novel insights about our evolution. Ultimately, however, these molecular findings can only be understood in light of data from field sites, morphology labs, and museum collections. Indeed, molecular anthropology depends on these sources for calibrating molecular clocks and placing genetic data within the context of key morphological and ecological transitions in human evolution.

Major histocompatibility complex and microsatellite variation in two populations of wild gorillas

In comparison to their close relatives the chimpanzees and humans, very little is known concerning the amount and structure of genetic variation in gorillas. Two species of gorillas are recognized and while the western gorillas number in the tens of thousands, only several hundred representatives of the mountain gorilla subspecies of eastern gorillas survive. To analyse the possible effects of these different population sizes, this study compares the variation observed at microsatellite and major histocompatibility complex (MHC) loci in samples of wild western and mountain gorillas, collected using a sampling scheme that targeted multiple social groups within defined geographical areas. Noninvasive samples proved a viable source of DNA for sequence analysis of the second exon of the DRB loci of the MHC. Observed levels of variation at the MHC locus were similar between the two gorilla species and were comparable to those in other primates. Comparison of results from analysis of variation at multiple microsatellite loci found only a slight reduction in heterozygosity for the mountain gorillas despite the relatively smaller population size.