Comparative thanatology, an integrative approach: exploring sensory/cognitive aspects of death recognition in vertebrates and invertebrates

Abstract

Evolutionary thanatology benefits from broad taxonomic comparisons of non-human animals' responses to death. Furthermore, exploring the sensory and cognitive bases of these responses promises to allow classification of the underlying mechanisms on a spectrum from phylogenetically ancient to more derived traits. We draw on studies of perception and cognition in invertebrate and vertebrate taxa (with a focus on arthropods, corvids, proboscids, cetaceans and primates) to explore the cues that these animals use to detect life and death in others, and discuss proximate and ultimate drivers behind their capacities to do so. Parallels in thanatological behaviour exhibited by the last four taxa suggest similar sensory-cognitive processing rules for dealing with corpses, the evolution of which may have been driven by complex social environments. Uniting these responses is a phenomenon we term 'animacy detection malfunction', whereupon the corpse, having both animate and inanimate attributes, creates states of fear/curiosity manifested as approach/avoidance behaviours in observers. We suggest that integrating diverse lines of evidence (including the 'uncanny valley' effect originating from the field of robotics) provides a promising way to advance the field, and conclude by proposing avenues for future research.This article is part of the theme issue 'Evolutionary thanatology: impacts of the dead on the living in humans and other animals'.

Death among primates: a critical review of non‐human primate interactions towards their dead and dying

“…Biological motion perception has been interpreted as a perceptual life detector common to vertebrates and understood as a tendency to attend to the semi‐rigid movements typically exhibited by animals (Johnson, ; Troje & Westhoff, ; Vallortigara & Regolin, ). Comparable results have been found in several species, including primates (reviewed in Gonçalves & Biro, ). In rhesus macaques, this information is processed in the superior temporal sulcus (STS) which shows homology to humans (Jastorff et al , ).…”

“…At a cognitive level, the corpse activates the CSA by virtue of its static cues to animacy, but because its affordances are that of an object, it also triggers the CSO. This perceptual mismatch creates a conflict in the two core systems, causing an animacy detection malfunction (Gonçalves & Biro, ). When a familiar individual is displayed in an unfamiliar configuration it triggers a complex chain of survival‐critical reactions, chiefly processed by the limbic system, which direct attention to potential danger.…”

“…Several species in the animal kingdom (eusocial insects, fishes and rodents) exhibit either/both necrophoric or necrophobic behaviours towards dead conspecifics. Such reflexive actions may be tied to predator evasion or pathogen avoidance mechanisms and are mostly triggered via chemoreception or olfaction (Gonçalves & Biro, ). Primates, however, unlike some animals guided primarily by olfaction, move in a multimodal realm, relying heavily on sight and sound, among other senses, to form an accurate perception of their environment (Ghazanfar & Santos, ).…”

“…Primates, however, unlike some animals guided primarily by olfaction, move in a multimodal realm, relying heavily on sight and sound, among other senses, to form an accurate perception of their environment (Ghazanfar & Santos, ). In this regard, it is not surprising that they show a diverse range of thanatological behaviours, from emotional ambiguity to exploratory actions that rather set them apart from the less‐flexible responses exhibited by other animals, which serve as an active way of gathering novel information about the corpse and the contextual cues that surround it – behavioural trends they share with corvids, proboscids and cetaceans (Gonçalves & Biro, ).…”

Jokro: The death of a wild infant chimpanzee from respiratory disease

“…Thanatology is the study of death and dying. Evolutionary thanatology aims to bring a comparative perspective to the field, by drawing together evidence from a range of different species (Anderson et al 2010;Gonçalves and Biro 2018). At present, we are facing a huge death toll caused by the COVID-19 outbreak.…”