Towards solving the evolutionary puzzle of suicide

Soper, Clifford Alan (2017) Towards solving the evolutionary puzzle of suicide. PhD thesis, University of Gloucestershire.

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Abstract

This doctoral thesis aims to formulate a theory that best accounts for the evolutionary origins of the human capacity for suicide - intentional, deliberate self-killing. In view of natural selection's 'survive and reproduce' rule of thumb, suicide constitutes an evolutionary puzzle (Confer et al., 2010). Following a review of the available alternative explanations, this thesis argues that suicidality most likely evolved as an unfortunate side­effect of two important primary adaptations in the human species, 'pain and brain': the aversive emotional experience of pain, which is biologically designed to aid self­preservation by motivating adaptive escape action; combined with a cognitive sophistication that offers most mature humans the means to escape pain maladaptively by self-killing. Suicide may thus be categorised alongside other major fitness costs of human cognition and encephalisation, such as obstetric complications arising from the parturition of large­skulled infants, and the necessity for human young to remain dependent on carers for many years while the brain develops, adaptive problems of such severity that they drove the natural selection of complex physiological and behavioural solutions to control their costs. Equally, the notion of suicidality as a costly by-product implies that countermeasures would expectably have evolved to prevent mature humans from using self-extinction to escape from pain. Sketching the likely parameters of such solutions, an engineering specification is proposed for a system of reactive, last-line anti-suicide defences, shiltons, biologically designed as a final defence against wilful self-killing. The specification includes, inter alia (a) an input trigger in the emotional experiencing of chronic, intense pain; (b) a developmental condition, recognising that a protective mechanism would be superfluous until the individual reaches the developmental stage, at around puberty, of being able to organise suicide, and ( c) potentially drastic output behaviours and mental states that would prevent suicides occurring most (but not all) of the time, by dulling the motivation to escape (pain-type) and/or by interfering with the individual's intellectual means to plan and enact a suicide endeavour (brain-type). It is suggested that the components and signature outcomes of this specification may be observed in a number of compulsive human responses to emotional pain, in symptoms of depression, addiction and other common mental disorders (CMDs) that occur alongside heightened suicide risk. The existence of shilton last-line defences, psychopathologies which themselves incur severe fitness costs, would point to the likelihood that a front line of defences, krols, would also have evolved. Pain-type krol systems, it is argued, would actively moderate the experiencing of negative affect in order to avoid the costly activation of shiltons: they may be observed in the homeostasis of affect at an above-neutral resting point; the phenomenon of self-serving self-deception; the pursuit of pleasurable interests and activities that apparently serve no direct biological purpose; and the selection and defence of unrealistically benign mental models of the world, which may often be religious. Other brain-type, krol mechanisms would block access to the idea of suicide through the cultural transmission of a taboo and moral strictures against the behaviour. Some implications of this theoretical framework are tentatively noted for suicide research, prevention strategies, and broader mental health policy. The proposed model offers theoretical grounding for the view that a search for usefully predictive biomarkers of suicide risk is unlikely to succeed, and that the most effective preventative solutions probably lie in public health measures to restrict access to lethal means.

Item Type:	Thesis (PhD)
Related URLs:	Organisation
Subjects:	H Social Sciences > H Social Sciences (General)
Divisions:	Schools and Research Institutes > School of Education and Applied Sciences
Depositing User:	Anne Pengelly
Date Deposited:	27 Apr 2022 13:33
Last Modified:	01 Sep 2023 16:05
URI:	https://eprints.glos.ac.uk/id/eprint/10965

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