Tuesday, March 23, 2010

Yet More Evidence that Suicide is Adaptive

The more babies you produce, the less likely you are to commit suicide (Reuters: The more kids, the lower moms' suicide risk).

This evidence supports the theory that suicide can be an adaptive behavior - people who commit suicide are people of low reproductive value anyway (i.e., those with few or no children and little likelihood of producing any viable offspring). Suicide may be an effective means of accomplishing one's evolved ends - "make sure your genes live on." When one consumes more than one contributes to one's relatives, one's continued existence is a drain on evolutionary fitness.

Of course, that's not how the study phrases it. Rather, motherhood is seen as having a "protective effect" against suicide - as if suicide were gonorrhea, and motherhood a condom.
Looking at 30 years' worth of data on 1.3 million Taiwanese mothers, [Dr. Chun-Yuh Yang, of Kaohsiung Medical University in Taiwan] found that women with two children were 39 percent less likely than those with one child to commit suicide.

That risk was 60 percent lower among women with three or more children, Yang reports in the Canadian Medical Association Journal.

Thus the species continues.

(As do I, despite speculation to the contrary.)

11 comments:

  1. Oh, you may claim to be alive, but if that isn't good enough for India's bureaucracy, should it be good enough for us?

    I can think of a way to compare the hypothesis that parenthood "protects" against suicide vs the suicidal are of low reproductive value: examine the suicide rates of parents after their children die.

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  2. From where I sit, the original post here was written by an alien from another planet.
    "Viable" offspring?
    Come ON.

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  3. From where I sit, the original post here was written by an alien from another planet.

    I get that a lot (argument ad alienus). Weirdly, so does TGGP, who believes the opposite of what I do on many issues.

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  4. TGGP, my thinking doesn't make the distinction you do.

    My claim is that an organism will look around at its situation and evaluate whether continuing to live makes sense in terms of "inclusive fitness." This would apply both to someone who hasn't had any children, and someone who has had children who have died.

    You could initially be of high reproductive value (e.g., you're a woman in your late thirties, have eight kids and it looks like many of them will survive to adulthood) and then lose all your expected reproductive value in one fell swoop (say, all your children die of diphtheria). Or you could have low reproductive value from the beginning. Either way, if one's expected contribution to one's inclusive fitness falls below one's expected drain on one's inclusive fitness, suicide is RATIONAL in terms of inclusive fitness, hence adaptive.

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  5. Glad to see you back on the beat!

    Richard Hoste, host of the race-realist blog, HBD-Books, has commented on this phenomenon in a handful of posts that I don't presently have time to look up. If I recall correctly, his take is that the inverse correlation between suicide and maternity stems from a kind of anomie that results when traditional gender roles are thrown into flux by cultural and political forces, such as feminism. Hoste's view is a bit ironic, given that he is otherwise disposed to embrace evolutionary explanations for pretty much anything and everything under the sun. He may not even be aware of the adaptationist theory of suicide.

    A kin-selective self-destruct sensor is consistent with the finding that a high percentage of suicides are impelled by the sense of being a burden to others, primarily kin. It would be interesting to gather "before and after" data on reproductive trends in the extended families of those who commit suicide. If there's an average spike against expectation, your theory would be strengthened.

    Also, I suggest that you set up an archive link titled "Is Suicide Adaptive?" in your blog margin.

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  6. Some behavioral economics arguments are being enlisted against suicide-choice here.

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  7. Chip, thanks, I will add that to the sidebar. And I have a data-obsessed friend I'm seeing tomorrow from whom I am going to try to get a lead on some possible sources for reproductive-trends-post-suicide.

    TGGP, thanks.

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  8. I'm not sure about this. First of all, the correlation isn't necessarily causative. I think women who have large families also tend to be members of the sort of religious group that would place heavy eternal penalites on suicide. Also, this does not explain the high suicide rates among older men and low suicide rates among older women. Under your theory, shouldn't suicide among post-menopausal women be extremely high? Even if they have children, those children probably do not rely on them anymore.

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  9. So I wouldn't say religiosity plays no role here, but a couple things:

    -female suicide rates are lower than male at every age
    -male suicide rates increase pretty linearly with age; but in many data sets, suicide rates peak for women at the menopause age.
    (see my trea

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  10. Oops - see my treatment in my post "How People Die By Suicide" for more support and sources.

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  11. I don't suppose Suicide Across the Life Span has data from China, where male and female suicide rates are similar. Such data might be determinative or at least extremely helpful here.

    At any rate, I'm not sure that the statistics of suicides among "older" women (the 35-44 peak in Canada barely qualifies as related to menopause) exhibit the pattern. If the difference between male and female suicide rates is mainly a factor of which methods of suicide are available, why is the female suicide peak so variable among Western countries?

    After re-reading the post on Joiner, though, I see what you are saying in context. The fact that we don't understand all the statistics on suicide doesn't mean that the adaptive model isn't still the best explanation.

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