Because we humans carry along our weaker species members, and protect them from otherwise fatal flaws. If the genetic flaw is relatively recent (within the timeframe of modern humans), then there’s no selectivity against it.
Darwin wrote about altruistic behavior like when a brother saves his family so more of his genes will survive. Thats not what youre talking about, but it sort of fits.
Humans do all sorts of things contra nature. We aren’t governed by instinct or `natural law’ beyond basic biology, so we can use our massively overdeveloped brains to make our freakishly hairless bodies do things completely unnatural, like voting Democratic or driving a station wagon. Suicide is one of those unnatural acts.
As for Darwinism, it only attempts to explain how species change over time and, eventually, become new species. Humans have thrown a wrench in that, too, with our mass eugenics programs instituted on cattle and wolves and grass and other things we’ve altered beyond recognition. Wheat, for example, is deformed to the point of being unsaveable, but humans keep the species going. Same with the wolves we’ve domesticated into dogs. Of course, we do the opposite for ourselves, carrying fundamentally weak members of society to childbearing years and beyond in the name of human decency and kindness and other group-oriented (as opposed to gene-oriented) concepts.
Well there’s no ‘mathematics gene’ or ‘making love to beautiful people gene’ either. Yet those things are both presumably under genetic control and have been selected for. Evolutionary processes can select for nebulous or intellectual traits like these simply by favouring those individuals most likely to engage in such behaviour, Suicide would be no different provided that such behaviour was favourable.
Given that we don’t know that it is genetic and so have no idea what the genetic mechanism is that question is impossible to answer.
Many traits that are survival disadvantages in their own right are propagated simply because they are linked to other traits that have a survival advantage. This linking can be direct, as in the case of genes promoting sickle cell anaemia also promoting disease resistance.
It can also be indirect, where the beneficial and detrimental genes are physically close together on the same chromosome through random chance. The detrimental gene is simply along for the ride and can’t be readily selected against until it mutates into less detrimental form.
Just to correct a possible misunderstanding of Blake’s last sentence: If a detrimental allele of one gene is physically close to a beneficial allele of another gene, there is much less opportunity to select against the detrimental allele (assuming it’s not as bad as the other gene is good), but occasionally the alleles will be separated (due to chromosones crossing over during meiosis). Once they end up on different chromosones, selection against the detrimental one is full speed ahead. It has nothing to do with either allele mutating into a different allele.
Wrong. Natural selection “allows” myopia because it is insufficiently disadvantageous to significantly lower the reproductive output of people with myopia. If a trait has no significant pressure against it, it will tend to persist in the population at a fairly steady proportion.
As for evolution only acting upon genes–well, that was the theory once upon a time, but we’ve discovered extra-genetic inheritence (like methylation patterns) since then. However, nucleic acid-borne genes are still the primary means of trait heritance.
And what might be a “fatal flaw” in a comic-book macho man fantasy could really be a negligible social cost compared to he benefit granted by the individual to society in general. Consider Dr. Hawking, for example.
People tend to take a wholly Darwinian view of Evolution, and ignore his oposite in the field: Kropotkin. Kropotkin argues that in addition to competition, mutual survival and communal support are just as vital to the evolutionary process. For human beings, social forces interact with individual forces to produce the psychology of an individual. This psychology is mostly non-genetic. Therefore, a society that promotes a negative psychology invariably finds itself less competitive (though perhaps more prolific ie palesitinians) than those with a positive psychology. A society whose suicide rates are high should reevaluate its social principles in the same manner that individuals who are suicidal should reevaluate their personal principles/ideas/etc.
While you’re quite right that crossing over can separate ‘paired’ genes that is not what I said, and it’s not what I meant. If the detrimental gene mutates into a more detrimental form it will be selected against.