Humans have an unusual strategy for dealing with infectious disease. Instead of avoiding contagious individuals, we provide them with extensive care. This enables us to control the spread of diseases through our population. Surprisingly, we know very little about how care-giving behaviours evolved. Care-giving hinges on a cognitive ability whose evolutionary origins are largely unknown: the ability to recognise disease in others. This project integrates comparative psychology, host-parasite biology, anthropology, and chemical ecology to begin to reconstruct the evolution of disease recognition in the primate order.
Primates are our closest living relatives, and like humans, are known for their social complexity, characterised by learning from others, cooperation, and coalitionary behaviour. The social pressures of managing these relationships are believed to have selected for increased cognitive abilities. However, the frequent, close proximity interactions that these behaviours require also increases the risk of disease transmission, making the ability to recognise disease highly advantageous.
The brain pathways integral to understanding social interactions (social cognition) in primates are likely to also be active in detecting disease symptoms. Subtle differences perceived in faces, voices, and odour may enable primates to not only decode others’ identities, emotions, and intentions, but also detect disease. This could include changes in facial colouration, shape and texture due to fever, rashes, weight loss, or nasal discharge, changes in vocalisations due to coughing, nasal discharge or reduced lung capacity, and changes in odour due to immune activation. Thus, if the detection of social information and disease involve the same brain pathways, then they may have evolved together.
Mandrills are ideal study subjects for this question because they are highly social and engage in complex communication, including striking facial colouration, elaborate vocalisations, and scent-marking behaviours. All of these cues have the potential to communicate health information.
This study integrates state-of-the-art methods from multiple disciplines (parasitology, digital imaging, bioacoustics, odour analysis, and cognition) to accomplish three objectives.
1: Test whether mandrill appearance, vocalisations, and odour signal parasite infections.
2: Test whether mandrills can detect disease via facial colouration, vocalisations, and scent-marks.
3: Test how disease recognition correlates with other types of cognition.
