Towards solving the evolutionary puzzle of suicide

Towards solving the evolutionary puzzle of suicide. C A Soper. PhD Thesis. DOI10.13140/RG.2.2.33063.04007

Abstract: How the potential for suicide – intentional, deliberate self-killing – came to evolve in the human species is a puzzle: it seems to defy the Darwinian axiom of natural selection, ‘survive and reproduce’. Searching for a solution, this thesis argues that suicide probably arose as a noxious by-product of two strongly advantageous adaptations: first, the emotional aversiveness of pain, an ancient biological stimulus that forces escape action; and second, the cognitive sophistication of the adult human brain, which unfortunately enables humans to escape pain by wilful self-extinction. These twin ‘pain and brain’ features are posited to be not only necessary but, in the absence of restraints or other means of escaping pain, sufficient conditions for suicide – they provide, respectively, the motive and the means. It follows that restraints would expectably have evolved to address suicide as a recurrent fitness threat. The likely characteristics of these defences are explored: protective systems would act, it is argued, to downgrade suicide’s ‘pain and brain’ drivers – emotional and intellectual faculties respectively – while allowing mental functioning to continue at an attenuated, usually survivable, level. Multiple lines of anti-suicide defences may account for symptoms of common mental disorders and certain other commonplace human behaviours and psychological states. Some implications are discussed, particularly with relevance to suicide prevention and the promotion of mental health.