

Wednesday, October 8, 2008

The Evolutionary Biology of Suicide: Is Suicide Adaptive?

















  1. Very thought-provoking post. Considering that suicide may at times be counter-adaptive, one wonders if it is, perhaps counterintuitively, a uniquely rational act--in that it's uniquely human.

    It seems to me only humans have the logical chops to make a cost-benefit analysis of life itself, measuring its worth against that of non-existence. Are there any other animals that choose suicide, that are able to transcend the daily exigencies of simple survival to escape their own personal vale of tears?

    Evolutionary psychology is fascinating, but I think it's important to remember that biology is not necessarily destiny. Obviously, not every mother or father who could further his or her own genes' survival by killing his or her offspring (by murdering stepchildren or sacrificing one child to benefit another) does so. They make ethical and rational choices to handicap their own genetic prospects. Similarly, suicide might be a choice that is not "rational" from the perspective of genetic survival but, ironically, serves a higher rationality.

    That said, I think suicide becomes difficult to justify even within a strictly utilitarian ethical framework. The emotional burden it puts on those around one likely far exceeds what comes with ordinary death. In that sense, it may indeed be rational to the suicide while nevertheless remaining highly unethical.

    Now, whether one has the right to suicide is another question entirely.
    1. Putting someone in a position where he or she wants to commit suicide is, in the antinatalist view, the primary unethical act. But if you ignore the imposition of birth and the suffering that life carries with it, suicide definitely causes suffering to one's friends and family. (So does natural death, but we don't blame the person for that - we blame nature.)
  2. There is another mechanism by which suicide is adaptive.

    If a person is valuable to the tribe, his suicide would harm the tribe. If his death would reduce the tribe's ability to survive significantly enough, it can be used as a threat to gain relative proportional resources.

    This is why you see overt suicidal behavior in teenagers more than in other ages. They have not *yet* been useful, but they are an investment, and it would be a waste to just get rid of this investment.

    Now, why does this result in actual suicides, rather than "mere" threats of suicide? Game theory holds the answer. For a threat to work, it must be credible. You wouldn't believe anyone was about to commit suicide if it never happened. However, if everyone who threatened to commit suicide was actually going to do it, it would be very costly and there would soon be people taking advantage of the free resources given to suicide threats. "Cries for help" suicide threats, as 'twere. It turns out the evolutionary stable strategy is a mix of genuine suicide threats with non-genuine resource-grabbing (cry for help) suicide threats.

    None of this happens consciously or even unconsciously. It just happens as a result of which game theoretical strategy produces the best inclusive genetic fitness.
    1. The reason I hold to this theory even though I've never seen an evolutionary psychologist or evolutionary biologist defend it is because I have seen it independently invented by many people who are familiar with both evolutionary psychology and game theory (but without degrees), and because it explains not only why there are suicides at all, but why there are true suicide threats and false suicide threats, why both are taken seriously, and why suicide is a low-status, degradable thing. It is only natural that a selfish resource-grabbing strategy that harms the tribe will be looked down upon.
    2. There's an interesting paper to the effect that people who attempt suicide but survive see an increase in income afterwards - the more serious the attempt, the bigger the boost in income. (I discuss this in the post on Joiner's book.) Also relevant: Attempted Suicide as a Signal, in which I argue that thwarting suicide attempts encourages insincere people to make them, at great cost to people who don't really want to die and people who want to die alike.
    3. This is why you see overt suicidal behavior in teenagers more than in other ages.

      Also, this is used to explain why (in our country, not in others) women attempt suicide more than men but men succeed more. Someone (maybe it's Posner) has a paper on choice of suicide method for optimal outcome, balancing the desire to survive with the desire for perceived lethality enough to trigger resource-influx. Women are more valued, the argument goes, so they can choose less-lethal methods and still get attention.

      Doesn't work for China and India, but it's an interesting idea. Joiner blames Confucianism for the China/India thing, but you could see it as a consequence of lower status of women in general. Still pretty ad hoc. I bet you could do better quantitatively.

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  3. Fear of death is not love of life.

  4. @Ian_HT completely my own fault of course







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  12. @bswud thanks!

  13. @realmattforney you're too real the rest of the time






  19. how are those belmont "marriages" going lol 

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