Adaptive Suicide

Rob Quinlan (C611417@MIZZOU1.MISSOURI.EDU)
Sun, 23 Oct 1994 18:25:53 CDT

I noticed a couple of postings about suicide which started me thinking. Now
I've come up with a couple ideas taht I'd like to test out on the list.

I think life-history theory (e.g. K. Hill 1993 Life-history theory in
evolutionary anthropology _Evolutionary anthropology_ Vol ?) might guide us
to cases where it is adaptive (in the evolutionary sense) to commit suicide.
Basically, evolutionary life-history theory provides models for making predicti
ons about the character of events in the course of an organisim's life. Some
of these events include: the timing of reproductive maturity, the timing of
first birth, length of the period of parental investment, reproductive
senescence, and death. For a phenotypic trait to be favored by natural
selection it must provide for more representation of an individual's genes
in future generations. Therefore, human life-histories should be reflective
of strategies that increase an individual's fitness. Under what circumstances
can suicide increase one's fitness?

It is adaptive to live as long as one has a chance of reproducing. And it is
adaptive to live as long as one can aid in the reproduction of other closely
related individuals. It is *not* adaptive to live when there is no chance of
reproducing *and* living results in a cost to fitness of one's close relatives.
Following this line we can predict suicide to occur in humans in certain
situations. However, before I suggest any hypotheses I probably ought to say
a few words to head off accusations of genetic determinism.

I don't know the statistics on the occurrence of suicide in this culture and
others, but I suspect that it is infrequent enough that it is not likely under
the control of one or a few genes. That is, there aren't very many situations
where it is adaptive to kill one's self so selection couldn't be maintaining
a gene for suicide. I suggest, then, that the decision to commit suicide is
the product of a mind evolved to track one's environment, assess one's self,
assess others, calculate costs and benefits, and motivate behavior based on
cost/benefit analysis. This evolved mind works through an extremely complex
system of preception, cognition, and emotion. What has been selected for is a
brain that makes adaptive decisions either consciously or not. Further, this
mind/brain is common to all humans in the same way livers are common to all
humans.

Hypotheses

1. People who have protracted, fatal diseases requiring long-term care and
significant economic and social expense for kin will kill themselves more
often than people in general.

2. People who are near the end of their lives, who no longer are able to aid
in the development and reproduction of their offspring and grand-offspring, and
who have a high probability of requiring long term care will kill themselves
more often than people in general.

2a. Old folks will kill themselves more often in societies where impediments
to mobility may be costs to fitness. Therefore, old nomads should commit
suicide more than old farmers.

2b. Elderly people will kill themselves more often in situations where the
cost of the care of old folks directly conflicts with the care of children or
with mating effort. Therefore, old poor people ought to kill themselves more
than old rich people.

2c. Old people should kill themselves more often in cultures where there are
few avenues of offsetting direct economic costs to kin of care for the elderly.
One situation when direct economic costs to kin of elderly care is offset is
when the elderly provide critical knowledge (perhaps specialist knowledge).
Therefore, old people in egalitarian societies ought to kill themselves more
often than old people in non-egalitarian societies. And elderly non-
specialists should kill themselves more than old specialists.

3. If the decision to commit suicide is generated by an evolved mind, then we
ought to see *maladaptive* suicides (ones not outlined above) occuring in
people with cognitive/affective disorders more often than among people in
general.

I can think of a couple more of these kinds of hypotheses, but that's enough
(if not too much) for now. Do any of you have comments or suggestions
regarding these hypotheses or this topic in general? Do any of you know
of published work on this subject? Do any of you know of ethnographic work or
mentions of suicide?

Sorry for this long posting and thanks for your indulgence.

Rob Quinlan, grad. student, dept of anthro, u. of missouri-columbia
c611417@mizzou1.missouri.edu