There is no robust evidence of nonhuman suicides, notwithstanding countless opportunities for such self-killings, if they occurred, to be documented by the world’s farmers, animal breeders, naturalists, and scientists. We are left with anecdote and fable, including the scorpion’s self-sting, proffered by Peña-Guzmán as an example of animal suicide despite clear evidence that scorpions cannot sting themselves to death.

Scorpions are immune to their own venom, presumably because selection has eliminated the germ lines of scorpions that were not so protected. The ubiquity of such specific, self-preserving adaptations connects to a third, theoretical, problem with animal suicide: the absence of a coherent explanation as to how selection could favour and maintain such a capability. […]

Suicide is not observed in nonhumans for a straightforward evolutionary reason: any genes that permitted suicide would have been eliminated along with the suicides’ bodies. Any animal that, in the absence of restraints, was capable of escaping its pain and suffering by self- killing would be expected to seize the opportunity, because some pain is unavoidable in the Malthusian theatre in which selection plays out, and because pain is designed to motivate action to escape. A suicidal animal, if it appeared, would face a predictable and severe adaptive problem – the kind of problem that selection would expectably and powerfully have addressed in the evolutionary past.

The most parsimonious explanation for the apparent absence of suicide among younger children, the severely cognitively impaired, and nonhuman animals, is that these populations lack the cognitive wherewithal to conceive and enact it.

{ Animal Sentience | PDF }

acrylic on canvas { Olivier Mosset, Untitled, 1970 }

animals, evolution | February 7th, 2018