Suicide

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Human Uniqueness Compared to "Great Apes": 
Likely Difference
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Suicide is the taking of one's own life intentionally. It is present among all human societies although the reported rates vary widely.  In most cultures it is related to age, with a variable peak in early adult life and an increase in late age, and a predominance in males.  Rates are increased in association with psychiatric illness, particularly schizophrenia and affective (manic-depressive) psychoses, but also neurotic disorders and personality deviations. There are no documented cases of suicide in great apes. A number of animal analogues of suicide have been reported, but none has clearly the characteristic of intention to end life, and in many cases details of the circumstances are obscure.

Timing

Timing of appearance of the difference in the Hominin Lineage as a defined date or a lineage separation event. The point in time associated with lineage separation events may change in the future as the scientific community agrees upon better time estimates. Lineage separation events are defined in 2017 as:

  • the Last Common Ancestor (LCA) of humans and old world monkeys was 25,000 - 30,000 thousand (25 - 30 million) years ago
  • the Last Common Ancestor (LCA) of humans and chimpanzees was 6,000 - 8,000 thousand (6 - 8 million) years ago
  • the emergence of the genus Homo was 2,000 thousand (2 million) years ago
  • the Last Common Ancestor (LCA) of humans and neanderthals was 500 thousand years ago
  • the common ancestor of modern humans was 100 - 300 thousand years ago

Possible Appearance: 
6,000 thousand years ago
Probable Appearance: 
160 thousand years ago
Definite Appearance: 
160 thousand years ago
Background Information: 

Suicide is recognised in all human populations, but at widely differing rates. Durkheim who was the first to undertake systematic studies maintained that suicide rates were a function of anomie or lack of coherence in society. More specifically rates are generally increased in those who are mentally ill, particularly with the psychoses (schizophrenia, schizoaffective illness and manic-depressive disorder) and are generally estimated as having a 10% lifetime risk by comparison with approximately 1% in the general population. Rates are also increased in physical disease, particularly when chronic and progressive.
 
Interestingly evidence from adoption studies suggests a genetic component in predisposition to suicide that is independent of psychiatric illness.
 
A reduction in suicide rates can be achieved for example by reducing the carbon monoxide content of coal gas, or the availability of certain analgesics.
 
Most studies show an increase in suicide with age, and an excess in males, but there are exceptions. Some national differences have been related to religion, rates in Catholic countries being generally lower, but such estimates are affected by tendencies to avoid legal registration of a death as a suicide.
 
Suicide is generally distinguished from attempted suicide or self injury, the age range and sex ratio of the latter being younger and less biased to males respectively.
 
The dependence of suicide rates on social factors is dramatically illustrated by the phenomena of kamikaze pilots and suicide bombers. the mass suicide of the Jones cult in British Guiana is also salutary.

The Human Difference: 

What is necessary for suicide to be recognised as such is that the individual has the concept of his own life and its discontinuation. Arguably such a concept depends upon the capacity for language.

Universality in Human Populations: 

There are no societies in which suicide is reliably reported to be absent.

Mechanisms Responsible for the Difference: 

A plausible explanation for the apparent difference between Homo sapiens and other species in predisposition to suicide is that only Homo sapiens has the capacity for symbolic representation that allows individuals to develop a concept of their own mortality and in some cases to come to the decision that the circumstances of life outweigh its preservation.

Possible Selection Processes Responsible for the Difference: 

Some cases of suicide are regarded as altruistic according to JBS Haldane's dictum that ' I will jump into the river to save two brothers or eight cousins ', but such logic applies to only a small minority of cases of suicide.

Occurrence in Other Animals: 

In his review Preti writes ' Naturalists have not identified suicide in nonhuman species in field situations, despite intensive study of thousands of animals species', and ' Sparse evidence supports some resemblance between the self-endangering behaviour observed in the animal kingdom, particularly in animals held in captivity or put under pressure by environmental challenges, and suicidal behaviour among humans '.

Related MOCA Topics
Referenced By:
Title Certainty
CDH12 (cadherin 12, type 2 (N-cadherin 2) ) Speculative
Self-Injury True

References

  1. Suicide among animals: a review of evidence., Preti, Antonio , Psychol Rep, 2007 Dec, Volume 101, Issue 3 Pt 1, p.831-48, (2007)