very very interesting view on the evolution, from the point of view of the small Dna fragments that survive if they manage to be transmitted to the next generations. A classic of science literature, deserving all its fame. Also the introduction of thvery very interesting view on the evolution, from the point of view of the small Dna fragments that survive if they manage to be transmitted to the next generations. A classic of science literature, deserving all its fame. Also the introduction of the concept of meme as cultural self-replicating object is interesting, even if probably not treated in a rigorous enough way...Continua Nascondi
Credo nel '76 abbia aperto gli occhi a molti. Se volete farvi aprire gli occhi leggetelo anche voi! Cambiera' il modo in cui vedete gli animali, le piante e l'uomo stesso, insomma tutte le "survival machines" come le chiama Dawkins:
"They arCredo nel '76 abbia aperto gli occhi a molti. Se volete farvi aprire gli occhi leggetelo anche voi! Cambiera' il modo in cui vedete gli animali, le piante e l'uomo stesso, insomma tutte le "survival machines" come le chiama Dawkins:
"They are in you and in me; they created us, body and mind...they have come a long way, those replicators. Now they go by the name of genes, and we are their survival machines [...]"...Continua Nascondi
se non ho capito male, il punto non e' se il DNA ha bisogno o meno di un organismo complesso per tramandarsi... all'inizio i "replicatori" erano ben diversi dal DNA di oggi e non necessitavano di macchine 'complesse'...l'evoluzione dei replicatori ha portato, tramite mutazioni successive e non volute, ad avere macchine (leggi organismi) sempre piu' complessi che li hanno supportati e hanno dato loro un vantaggio... credo sia il nuovo rapporto di causa-effetto introdotto in questo libro il suo vero successo: i geni hanno "usato" gli organismi per propagarsi e non il contrario cioe' gli organismi non hanno usato i geni come trucco o mezzo per riprodursi...
[The war of attrition] can be thought of as arising in a species that never engages in dangerous combat, perhaps a well-armoured species in which injury is very unlikely. All disputes in this species are settled by conventional posturing. A contest a[The war of attrition] can be thought of as arising in a species that never engages in dangerous combat, perhaps a well-armoured species in which injury is very unlikely. All disputes in this species are settled by conventional posturing. A contest always ends in one rival or the other backing down. To win, all you have to do is stand your ground and glare at the opponent until he finally turns tail. Obviously no animal can afford to spend infinite time threatening; there are important things to be done elsewhere. The resource he is competing for may be valuable, but it is not infinitely valuable. It is only worth so much time and, as at an auction sale, each individual is prepared to spend only so much on it. Time is the currency of this two-bidder auction.
Suppose all such individuals worked out in advance exactly how much time they thought a particular kind of resource, say a female, was worth. A mutant individual who was prepared to go on just a little bit longer would always win. So the strategy of maintaining a fixed bidding limit is unstable. Even if the value of the resource can be very finely estimated, and all individuals bid exactly the right value, the strategy is unstable. Any two individuals bidding according to this maximum strategy would give up at exactly the same instant, and neither would get the resource! It would then pay an individual to give up right at the start rather than waste any time in contests at all. The important difference between the war of attrition and a real auction sale is, after all, that in the war of attrition both contestants pay the price but only one of them gets the goods. In a population of maximum bidders, therefore, a strategy of giving up at the beginning would be successful and would spread through the population. As a consequence of this some benefit would start to accrue to individuals who did not give up immediately, but waited for a few seconds before giving up. This strategy would pay when played against the immediate retreaters who now predominate in the population. Selection would then favour a progressive extension of the giving-up time until it once more approached the maximum allowed by the true economic worth of the resource under dispute.
Once again, by using words, we have talked ourselves into picturing an oscillation in a population. Once again, mathematical analysis shows that this is not correct. There is an evolutionarily stable strategy, which can be expressed as a mathematical formula, but in words what it amounts to is this. Each individual goes on for an unpredictable time. Unpredictable on any particular occasion, that is, but averaging the true value of the resource. For example, suppose the resource is really worth five minutes of display. At the ESS, any particular individual may go on for more than five minutes or he may go on for less than five minutes, or he may even go on for exactly five minutes. The important thing is that his opponent has no way of knowing how long he is prepared to persist on this particular occasion.
Obviously, it is vitally important in the war of attrition that individuals should give no inkling of when they are going to give up. Anybody who betrayed, by the merest flicker of a whisker, that he was beginning to think of throwing in the sponge, would be at an instant disadvantage. If, say, whisker-flickering happened to be a reliable sign that retreat would follow within one minute, there would be a very simple winning strategy: "If your opponent's whiskers flicker, wait one more minute, regardless of what your own previous plans for giving up might have been. If your opponent's whiskers have not yet flickered, and you are within one minute of the time when you intend to give up anyway, give up immediately and don't waste any more time. Never flicker your own whiskers." So natural selection would quickly penalize whisker-flickering and any analogous betrayals of future behaviour. The poker face would evolve.
Why the poker face rather than out-and-out lies? Once again, because lying is not stable. Suppose it happened to be the case that the majority of individuals raised their hackles only when they were truly intending to go on for a very long time in the war of attrition. The obvious counterploy would evolve: individuals would give up immediately when an opponent raised his hackles. But now, liars might start to evolve. Individuals who really had no intention of going on for a long time would raise their hackles on every occasion, and reap the benefits of easy and quick victory. So liar genes would spread. When liars became the majority, selection would now favour individuals who called their bluff. Therefore liars would decrease in numbers again. In the war of attrition, telling lies is no more evolutionarily stable than telling the truth. The poker face is evolutionarily stable. Surrender, when it finally comes, will be sudden and unpredictable....Continua Nascondi