Convergent? Minds? Some questions about mental evolution

Abstract

In investigating convergent minds, we need to be sure that the things we are looking at are both minds and convergent. In determining whether a shared character state represents a convergence between two organisms, we must know the wider distribution and primitive state of that character so that we can map that character and its state transitions onto a phylogenetic tree. When we do this, some apparently primitive shared traits may prove to represent convergent losses of cognitive capacities. To avoid having to talk about the minds of plants and paramecia, we need to go beyond assessments of behaviourally defined cognition to ask questions about mind in the primary sense of the word, defined by the presence of mental events and consciousness. These phenomena depend upon the possession of brains of adequate size and centralized ontogeny and organization. They are probably limited to vertebrates. Recent discoveries suggest that consciousness is adaptively valuable as a late error-detection mechanism in the initiation of action, and point to experimental techniques for assessing its presence or absence in non-human mammals.

Keywords: animal consciousness; comparative psychology; evolutionary convergence; mental evolution.

Figure 1.

Phylogeny of mirror-test performance in hominoids. Taxa that pass the Gallup test by touching marks on their faces when they look in a mirror are indicated by stars. Gibbons (grey text) do not pass the test, but what this means is unclear, because they also show no interest in directly visible marks on their arms. Published analyses of Gallup-test performance [25,26] posit an initial gain (G) of self-awareness in the ancestral great ape and a secondary loss (L) in the gorilla lineage (white boxes). But it is equally parsimonious to assume that test-passing ability evolved convergently in the Pongo lineage and the common ancestry of the Pan–Homo clade (black squares). (Phylogram after [13].)