Suicide and natural selection?

Question

How does suicide fulfill the criteria of natural selection?

Answer 1

I don't believe there is any evolutionary basis for mental disorders, they're just a by-product of us attempting to adapt to an artificial environment (admittedly of our own making, but still artificial nevertheless). Primitive humans don't sit 8 hrs/day in front of a flickering screen in a cloth-lined cubicle, they don't have to pay bills and mortages, they probably don't understand the ramifications of layoffs and divorces. Depression and suicide are mostly the result of us unable to come to terms with the stress instilled by our artificial environment.

People point to serotonine and other neurotransmitters and dysfunctional reward pathways as a genetic basis of depression, but these genetic susceptibility are meaningless without environmental triggers...and most of these environmental triggers did not exist for our ancestors.  I'm sure the suicide rate of medieval europe is considerably lower than our present rates, even though we have pretty much the same genetic makeup.

Answer 2

I'm assuming the question here is: how can 'behaviour' such as suicide exist as surely it is counter productive to an individual's survival and therefore should have been selected against?

If a hypothetical population had a hypothetical gene (and it can only be due to genetic, not environmental pressures, else the effect cannot be passed on to another generation) that caused an organism to kill itself prior to raising young in an effective manner - i.e. surviving to adulthood - then natural selection would obviously select against such genes. If it causes the organism to suicide after this time, then it cannot be selected against.

If the tendency for suicide is mainly environmental, and I'd suggest it is in the majority of cases (pressure of work / stress / bereavement / drugs), then it will not be selected against - even a suicidal tendency (a genetic basis for depression for example) may not be eradicated as not all individuals with that gene will necessarily commit suicide.

It's the similar argument as to why malignant cancer should survive when surely natural selection should reduce the risk over time. Provided the cancer doesn't become active until post-child bearing age, there is no selective pressure to remove it from the gene pool. Hence a tendency for cancers to hit the elderly and to be rare in children.

HTH

Mike

Answer 3

IF you live long enough to reproduce, then you have survived the pressure of natural selection.  If you are suicidal, and you pass that characteristic on to the next generation (with the assumption that it is a heritable characteristic), then you increase the probability that you will have a child with a similar trait from a mate, and decrease the probability of having that child survive long enough to reproduce.

ON the other hand, if the characteristic that leads to suicide is appealing to a mate -high intelligence, broody moods but killer good looks- you balance out the selective pressure and can keep whatever heritable trait around for a long time.  Assuming of course that the trait is heritable.

Answer 4

only the strong survive.... thats the rule of natural selection.

Only the MENTALLY and Physically strong.... so just as someone with AIDS will die from physical problems.. someone with serious clinical depression problems will die from mental problems (in suicide).

So, its just a means to an inevitable end.  

Answer 5

First of all it's survival of the FITTEST, not strongest. Mental disorders such as depression (the most typical cause of suicide) are relative newcomers in terms of evolution. The rise in the prevalence of mental disorders correlates with increased longevity (life span). The symptoms of most mental disorders arise after puberty, and thus for our evolutionary ancestors (EAs), post-reproduction. Furthermore, our EAs did not live long enough for the genes coding for mental illness to express themselves. So, evolutionary psychologists regard mental illnesses as being either non-adaptive by-products of genes that were adaptive for our EAs, or as non-adaptive genes that did not get weeded out since the effects of these genes do not appear until after reproduction had occurred.  

Answer 6

It doesn't.

When an organism finds itself in an evironment quite different from the one in which it evolved, then many pathological (non-natural) behaviors can arise.   There is no reason to think that suicide occurred at all in early humans, any more than we see other primates taking their own lives.   It is more likely the result of human beings unable to cope with the artificial environment and pressures of modern human society, and of endochrinological problems that are outside the normal range for humans, that in the wild would not be fatal.