Questo è il tredicesimo post di una serie dedicata alla teoria dell'evoluzione per selezione naturale. Siamo nel libro di Richard Dawkins "Il Gene Selfish, 1976. The translation is mine.
Here are links to all the episodes: 1 , 2, 3 , 4, 5 , 6, 7 , 8, 9 , 10, 11 , 12, 13, 14 .
this episode begins with the most beautiful and surprising book.
We have already seen that the genes "plan" our brain by providing general strategies to follow. From that moment on, genes are naturally selected based on quality of strategies that produce . The surprising thing, that we will see from today is that genes that are selected are those that plan in the brains altruism, generosity and kindness. short, all these basic feelings have been created by natural selection. The reason is that there are genes that produce a brain selfless increase their chances of survival compared with genes that produce a brain is completely selfish. Of course we should not expect that altruism and kindness of the machines for survival are indiscriminate and unlimited: the genes of success are those that produce brain capable of altruism in some cases and selfishness in other cases. Now begins a long series of posts that illustrates many examples of these mechanisms. This post is especially important because introduces game theory and the concept of evolutionarily stable strategy (ESS). The word to Dawkins.
Chapter 5
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For a survival machine, another survival machine (which is not his son or another close relative) is part of the environment , as a rock or a river or a piece of food. It 's something that gets in the way or something that can be exploited. It differs from the rocks and rivers to an important aspect: it tends to respond if it is hit. This is because it too is a machine which contains its own geniuses in trust for the future, and also will stop at nothing to preserve them. Natural selection favors those genes that control their survival machines in order to exploit the environment in the best way . This includes take advantage of other survival machines, both of the same species of different species.
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machines survival of different species influence each other in various ways. They may be predators or prey, parasites or hosts of parasites, or in competition for scarce resources. Survival machines possono essere sfruttate in vari modi. [Ad esempio, le orchidee inducono le api a copulare coi loro fiori, a causa della loro forte somiglianza con le api femmine. Ciò che l'orchidea ottiene da questo inganno è l'impollinazione, perché un'ape che venga ingannata da due orchidee trasporterà il polline dall'una all'altra. Come altro esempio, le lucciole attraggono i loro partner lampeggiando di fronte a loro. Ogni specie di lucciola ha la sua particolare sequenza di lampeggio, il che impedisce la confusione tra le varie specie, e la conseguente dannosa ibridazione. Proprio come i marinai ricercano la sequenza di lampeggio di un preciso faro, le lucciole ricercano sequenze della propria specie. Le femmine del genere Photuris hanno "Discovered" that can attract the males of the genus Photinus mimic the code if the flashing of a female Photinus . So they do, and when a male Photinus nell'imbroglio falls and approaches the female, it is summarily eaten.]
survival machines of the same species tend to influence more directly with each other. This for many reasons. One is that half the population of your own species could be a potential mating partner, and a tireless and exploitable parent for your children. Another reason is that members of the same species, since machines to preserve the genes in the same type of environment, with the same stile di vita, competono tra loro in modo particolarmente diretto per tutte le risorse necessarie per vivere. Per un merlo, una talpa può essere un concorrente, ma non un concorrente tanto importante quanto un altro merlo. I merli e le talpe possono competere per i vermi, ma un merlo e un altro merlo competono tra loro per vermi e ogni altra cosa. Se sono membri dello stesso sesso, possono competere anche per i partner di accoppiamento. Per ragioni che vedremo, sono di solito i maschi che competono tra loro per le femmine. Questo significa che un maschio potrebbe dare beneficio ai propri geni se produce qualche danno a un altro maschio con cui è in competizione.
Potrebbe quindi sembrare che la politica più logica sia assassinare rivals and then eat them instead. Although the murder and cannibalism in fact occur in nature, are not as common as naive interpretation of the selfish gene theory seems to predict. Konrad Lorenz, on aggression, its emphasis on nature, "as gentlemen" of fighting between animals. For him, the remarkable thing about the fights between animals is that they are formal tournaments, fought according to rules such as boxing or fencing. The animals fight with boxing gloves and blunt swords. Threats and bluffs take the place of [deadly earnest]. I made gestures are recognized by the victors, they fail to give that final blow that our folk theory would predict.
[...] Although it has been overstated, this view "sport" of fighting animals seems to have some truth. On the surface it seems a form of altruism. The selfish gene theory is faced with the difficult task of explaining it. Why Animals Do not just kill members of their species rivals whenever they can?
The general answer is that the indiscriminate pugnacious, and providing benefits, it also has costs, and not just the obvious costs in terms of time and energy. For example, suppose that B and C are both my opponents, and I happen to meet B. It might seem reasonable that I, as a selfish individual, to try to kill him. But wait. Even C is my rival, and C is also rival B. Killing B, I'm potentially doing a favor to C, eliminating one of its rivals. It might be better for me to leave alive B, because then he could compete or fight with C, thus indirectly benefiting me. The moral of this simple hypothetical example is that there is an obvious advantage in trying to indiscriminately kill their rivals. In a large and complex system of rivalries, to eliminate a rival from the scene is not necessarily good: other rivals could benefit from his death more than me. This is the hard lesson learned by the officials of pest control. You have a serious pest that threatens agriculture, a good way to discover destroying them, and do, only to discover that another parasite benefits from its elimination even more than does agriculture, and you end up worse off than before.
On the other hand, might seem like a good plan to kill, or at least fight, rivals some special selectively. If B is an elephant seal that has a large harem of females, and I, another elephant seal, I killing him acquire his harem, could defendant attempted to kill him. But there are costs and risks in a pugnacious selective. E 'interest in B respond to the attack, to defend his valuable property. If I start a fight, I have the same chance of dying that has him. Maybe anche di più. Lui possiede una risorsa di valore, ed è per questo che lo voglio sfidare. Ma perché la possiede? Forse l'ha vinta in combattimento. Probabilmente ha sconfitto altri sfidanti prima di me. E' probabilmente un bravo combattente. Anche se io vincessi ed ottenessi l'harem, potrei uscirne così malconcio da non poterne trarre beneficio. Inoltre, combattere consuma tempo ed energia. Potrei far meglio a conservarli per adesso. Se mi concentro nel cibarmi e a tenermi fuori dai guai per un po', diventerò più grande e più forte. Prima o poi lo sfiderò, ma, se aspetto, potrei avere maggiori possibilità di vincere.
Questo soliloquio soggettivo è solo un modo di evidenziare che la decisione se combattere or not should be preceded by a complex (albeit unconscious) cost-benefit assessment. The potential benefits are not all on the side of the fight, although some of them undoubtedly are. Similarly, during the fight, every tactical decision whether to continue the fight or flight has costs and benefits, in principle, can be gauged. Ethologists have understood for a long time, but it was necessary the genius of John Maynard Smith, not generally regarded as an ethologist, to express this idea clearly and decisively. [...] He uses the branch of mathematics known as Game Theory . Its elegant ideas can be expressed in words without resorting to mathematical symbols, although for a small price in terms of accuracy.
The essential concept introduced by Maynard Smith is to evolutionarily stable strategy, an idea that dates back to WD Hamilton and RH MacArthur. A "strategy" is a policy of pre-programmed behavior. An example of the strategy is "Attack the opponent flees if Pursue; responds to the attack if it escapes." It 'important to understand that we are not thinking about the strategies as if they were consciously implemented by individuals. Remember that we are portraying the animal as a robot survival machine with a pre-programmed computer that controls the muscles. Represent the strategy in the English language is our only convenient way of thinking. Through some mechanism not specified, the animal behaves as if was following those instructions.
An "evolutionarily stable strategy" or ESS, is defined as a strategy that, if adopted by most members of the population, can not be improved by an alternative strategy. E 'subtle and important idea. Another way of putting the matter is that say that the best strategy for an individual depends on what makes the majority of the population. As the rest of the population consists of individuals, each of which is trying to maximize their happened, the only strategy che persiste nella popolazione sarà quella che, una volta diffusa nella popolazione, non può essere migliorata da un individuo che cerchi di cambiarla. Se c'è un repentino cambiamento nell'ambiente, subito dopo ci può essere un breve periodo di instabilità evolutiva, forse anche un'oscillazione nella popolazione. Ma una volta che una ESS si è diffusa nella popolazione, rimarrà: la selezione penalizzerà le deviazioni da essa.
(nel prossimo episodio cominceremo a vedere esempi pratici)
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