Primate social cognition: uniquely primate, uniquely social, or just unique?

Primates undoubtedly have impressive abilities in perceiving, recognising, understanding and interpreting other individuals, their ranks and relationships; they learn rapidly in social situations, employ both deceptive and cooperative tactics to manipulate companions, and distinguish others’ knowledge from ignorance. Some evidence suggests that great apes recognize the cognitive basis of manipulative tactics and have a deeper appreciation of intention and cooperation than monkeys; and only great apes among primates show any understanding of the concept of self. None of these abilities is unique to primates, however. We distinguish (1) a package of quantitative advantages in social sophistication, evident in several broad mammalian taxa, in which neocortical enlargement is associated with social group size; from (2) a qualitative difference in understanding found in several distantly related but large-brained species, including great apes, some corvids, and perhaps elephants, dolphins, and domestic dogs. Convergence of similar abilities in widely divergent taxa should enable their cognitive basis and evolutionary origins to be determined. Cortical enlargement seems to have been evolutionarily selected by social challenges, although it confers intellectual benefits in other domains also; most likely the mechanism is more efficient memory. The taxonomic distribution of qualitatively special social skills does not point to an evolutionary origin in social challenges, and may be more closely linked to a need to acquire novel ways of dealing with the physical world; but at present research on this question remains in its infancy. In the case of great apes, their ability to learn new manual routines by parsing action components may also account for their qualitatively different social skills, suggesting that any strict partition of physical and social cognition is likely to be misleading

Western Gorilla Social Structure and Inter-Group Dynamics

The study of western gorilla social behaviour has primarily focused on family groups, with research on inter-group interactions usually limited to the interactions of a small number of habituated groups or those taking place in a single location. Key reasons for this are the high investment of time and money required to habituate and monitor many groups simultaneously, and the difficulties of making observations on inter-group social interaction in dense tropical rainforest. However, gorilla groups are known to have extensively overlapping home ranges, show affiliative inter-group interactions and often aggregate at resource hotspots. There is also genetic evidence of kin-biased behaviour between dispersed kin. This is all suggestive of a complex society in which inter-group interactions may follow an underlying multi-level social structure where affiliations are influenced by kinship, social exposure, ranging patterns, territoriality or foraging decisions. This thesis investigates the large scale society of western lowland gorillas, using novel technologies and analytical methods to overcome the considerable difficulties in studying large numbers of gorillas simultaneously. I use biases in movement patterns to investigate the cognitive rules used, and decisions made by this intelligent, social species, to navigate the limited space and resources they share with their neighbours. Using observational data from two forest clearings in the Republic of Congo, I quantify community structure by network modularity analysis and hierarchical clustering, demonstrating the presence of kin-based multi-level social structure in western lowland gorilla. The sizes of these gorilla social units follow a hierarchical scaling pattern similar to that observed in other mammalian multi-level societies including humans. The social structure detected at these forest clearings is consistent with a super-spreader structure, suggesting that clearings may act as important transmission hubs for disease, novel ideas, behaviour or culture. This demonstrates that intervention strategies targeting gorillas with home ranges near to forest clearings, particularly solitary males, may be highly effective for limiting the transmission of certain diseases. Modelling the movement patterns of a gorilla population across their ranges using camera trap data demonstrates that gorilla groups appear to actively avoid one another, both through avoidance of other groups at resource hotspots, and avoidance of areas regularly used by other groups. Gorilla groups visit sites less often the closer they are to another group’s home range centre, with groups avoiding larger, more dominant group’s home range centres to a greater extent. This, along with the increased avoidance of visiting a location on the same day as another group when close to their home range centre, is highly suggestive of the presence of territorial defence in western gorillas. The findings in this thesis demonstrate the presence of a kin-based multi-level social structure in western gorillas, with considerable similarities to that present in humans, suggesting that a key component of human social complexity may have evolved far earlier than previously asserted. They suggest that the social brain enhancements observed within the hominin lineage were not necessary to enable human multi-level social structure. I show that western gorillas demonstrate biases in their movement patterns consistent with the presence of some broader elements of territoriality, with regions of priority or even exclusive use, close to their home range centres. My findings strongly emphasise the importance of gorillas as a model system for human social evolution. This is due to both the common underlying multi-level social structure and the considerable similarities in inter-group territorial dynamics. In contrast to previous assumptions that interactions between gorilla groups are primarily random or due to aggressive mate competition, I find that these interactions appear to be based around a complex social structure influenced by kinship, territoriality and dominance.The Nacey Maggioncalda foundation, the International Society for Human Ethology, Sabine Plattner Africa Charities, the University of Cambridg

The Evolution of Diversity

Since the beginning of time, the pre-biological and the biological world have seen a steady increase in complexity of form and function based on a process of combination and re-combination. The current modern synthesis of evolution known as the neo-Darwinian theory emphasises population genetics and does not explain satisfactorily all other occurrences of evolutionary novelty. The authors suggest that symbiosis and hybridisation and the more obscure processes such as polyploidy, chimerism and lateral transfer are mostly overlooked and not featured sufficiently within evolutionary theory. They suggest, therefore, a revision of the existing theory including its language, to accommodate the scientific findings of recent decades

Life on the ground: the behavioural ecology of risk and terrestriality in primates

The spread of predation risk across an environment creates a “landscape of fear” that acts as a significant driver of behaviour and evolution in prey species. This thesis explores primates’ landscapes of fear, with a particular focus on the relationship between perceived risk, substrate use, and the evolution of primate – including human – locomotion. Chapter One provides an introduction and overview of the landscape of fear concept, how it might have featured in the paleoenvironments of early hominins, and how it is studied in extant primates. Chapter Two presents a quasiexperimental study of risk perception in baboons in Gorongosa, Mozambique. In this study, habituation by human observers is used to document relationships between perceived risk of humans, mediating environmental variables, and behavioural correlates in two baboon troops. The results demonstrate that behaviours indicative of perceived risk – vocalisations and vigilance – decline throughout habituation and are mediated by habitat structure and time of day. There is also a negative relationship between these behaviours and baboons’ use of the ground. Chapters Three and Four explore this relationship between risk and ground-use at broader scales and using the presence of carnivores, rather than humans, as indicators of risk. In Chapter Three, camera trap data provides insight into the effects of ecology, season, and risk on the terrestrial activity patterns of two neighbouring baboon populations in Mozambique. The results illustrate that seasonality influences baboons’ use of the ground, and suggest that circadian patterns in terrestrial activity are sensitive to predator abundance or species in a landscape. Chapter Four investigates these dynamics at an even broader scale, comparing carnivore and baboon activity across 10 different sites in eastern and southern Africa. Results from this chapter indicate that loss of carnivore diversity – and particularly the absence of leopards – releases restrictions on baboon terrestriality, facilitating their use of the ground during crepuscular and nocturnal hours. Finally, Chapter Five returns to an evolutionary perspective with a review of the origins of hominin locomotion and the emergence of primate terrestriality. This chapter emphasises the value of integrating paleontological research with insights from behavioural ecology to generate more nuanced understandings and hypotheses about the environments that have shaped human evolution