Maryl Monroe Peircing

This is the fourth post in a series devoted to the book by Richard Dawkins "The Blind Watchmaker : as evidence evolution reveals a universe without a conscious designer. "The translation of the book and is different from that in my library. To view all the posts in the series, click the label" The Blind Watchmaker "or label" evolution, "in the sidebar of the blog.


In this episode, which is one of the most important Dawkins is addressing a claim by supporters of intelligent design, which says more or less:" The mechanism of Darwin can work, because it suggests that mutations must be small enough to be able to verify the case, but large enough by give a survival advantage. These two requirements contradict each other. For example, as the insects may have evolved leaf that are camouflaged with leaves? The initial similarity to a leaf must be small enough not to give any advantage camouflage. "

Dawkins' answer to this apparent paradox is really enlightening. Not to be missed for any reason. The episode is also very funny, including the other. The word Dawkins.



Chapter 4 (cont'd)

This type of problem has to think of those who study animals that are protected from predators by camouflage . The " stick insects" look like a twig, and thus can not be eaten by birds. The leaf insects look like leaves. Many edible species of butterflies obtain protection because of their similarity with harmful or poisonous species. These similarities are more striking similarity to a cloud in a weasel.

We use the word camouflage for these cases, not because we think that animals consciously imitate other things, but because natural selection favored those individuals whose bodies were exchanged for other things. To put in other words, the ancestors of the leaf insects that looked like leaves non lasciavano discendenti. Il genetista tedesco-americano Richard Goldschmidt è il più noto tra coloro che hanno sostenuto che la selezione naturale non avrebbe potuto favorire l'evoluzione iniziale di queste somiglianze. Gould, che era un ammiratore di Goldschmidt, disse a proposito degli insetti che imitano gli escrementi: "Può forse esserci un vantaggio ad assomigliare al 5% a uno stronzo?". In gran parte grazie all'influenza di Gould, recentemente è diventato di moda dire che Goldschmidt fu sottovalutato durante la sua vita, e che in realtà ha molto da insegnarci. Ecco un esempio del suo modo di ragionare.

Ford parla... di qualunque mutation that can confer a 'remote similarity' to a protected species, from which similarity might derive some advantage, however slight. We must ask ourselves how this can be remote similarity to have a selective value. Can we really suppose that the birds and monkeys and even the mantids are such great observers (or may have some of them particularly able) to note a 'remote' similarity and ignore the prey because of this similarity? I think that's asking too much.

Such sarcasm is directed against anyone who comes into an area so shaky as that modeled here by Goldschmidt. Observers wonderful? Some them particularly skilled ? Does anyone think that birds and monkeys have benefited from being deceived by remote resemblance? Semmai Goldschmidt should have said: "We can assume that the birds have really looked so mediocre (or some of them that they are particularly stupid)?".

Nevertheless, it is true that we have here is a puzzle. The similarity between the original ancestor of a branch and stick insect must have been very remote. A bird should have a vision very mediocre to be deceived. Yet the likeness of a stick insect to a modern branch is incredibly large, up to the most minute details of the false gems and false leaf scars. The birds, whose selective predation has given the final touch to the evolution of insects, must have had at least a whole, having a very good . Must have been extremely difficult to deceive, otherwise the insects would evolve to the levels we see today in perfect mimicry: would remain in a state of relatively imperfect mimicry. How can we resolve this apparent contradiction?

One possible answer suggests that the sight of birds has evolved in the same span of time evolution of mimicry in insects. Perhaps to put it jokingly, that looked like an insect ancestral only 5% to an asshole managed to fool an ancestral bird that had only 5% of view. But this is not the answer I want to give. In fact there is reason to believe that the whole process of evolution of mimicry, the remote resemblance to the almost perfect mimicry, has occurred many times independently, and quickly, in several insect groups, during a time when the sight of birds is remained roughly as good as today.

[...]

prefer another explanation. Namely, that no matter how good the sight of a predator under certain conditions, it can be extremely mediocre in other conditions. In fact, based on our own personal experience, we are easily able to appreciate the full scope of change by having a very imperfect in an excellent view. If I look directly a stick insect, 20 inches from my nose and into the light, I do not let fool you. I will notice the long legs that run along the line of the chest and abdomen. I could identify the unnatural symmetry that would not have a real twig. But if I, with the same eyes and the brain itself, I'm walking in a forest at dusk, I might not realize all the insects dark about the many branches and twigs. The image of the insect could be projected to the periphery of my retina, rather than in the central part which is more acute. The insect could be 10 meters away and projecting an image on my retina just tiny. The light could be so poor not show me practically nothing.

In fact, no matter how remote, how imperfect is the resemblance of an insect to a stick, there must be a some degree of shade, or some degree of distance from the eye of the predator, or some degree of distraction of the predator, that even a very sharp eye will be tricked by this resemblance remote. If this does not seems plausible for a particular example you have in mind, just a little diminuiate the amount of light in the scene you imagined, or whether you are traveling a bit 'to the object imagery! The point is that more than one insect was rescued by a surprisingly small resemblance to a twig or a leaf or excrement, on an occasion when he was very far from the predator, or on an occasion when the predator was watching him at sunset, or through the fog, or was watching him while he was distracted by a receptive female. And more than one insect has been saved, perhaps from the same predator, a very good resemblance to a twig, on one occasion in which the predator was watching him closely and in relatively good light.

La cosa importante nell'intensità della luce, nella distanza dell'insetto dal predatore, nella distanza dell'immagine dal centro della retina, e in tutte queste variabili, è che sono tutte variabili continue . Variano di quantità piccolissime e infinitesimali ricoprendo tutta la gamma, dall'estremo dell'invisibilità all'estremo della visibilità. Queste variabili continue promuovono un'evoluzione continua e graduale.

Il problema di Richard Goldschmidt -- che fu uno di una serie di problemi che lo convinsero ad adottare, nella maggior parte della sua vita professionale, la convinzione estrema che l'evoluzione proceda per grandi balzi piuttosto che per piccoli passi -- si è rivelato un falso problema. E tra parentesi, abbiamo dimostrato ancora una volta a noi stessi che una vista al 5% è meglio dell'assenza di vista. La qualità della mia vista alla periferia della retina è probabilmente ancora meno del 5% della qualità al centro della mia retina, se proprio vogliamo dare una valutazione quantitativa della qualità. Eppure, guardando con la coda dell'occhio, io riesco ancora a percepire la presenza di un grande autocarro o di un autobus. Poiché ogni giorno vado a lavorare in bicicletta, qualche volta questo fatto mi ha probabilmente salvato la vita. Mi accorgo della differenza con i giorni in cui piove e porto un cappello. La qualità della nostra visione in una notte buia dev'essere much less than 5% of what is at noon. Yet most of our ancestor was probably saved from having seen something truly important, such as a tiger fangs like a saber, or a precipice, in the middle of the night.

Each of us knows from personal experience, gained in such a dark night, that there is a continuum, gradually, the tiny nuances, which covers the entire range from total blindness to perfect vision, and that every step in this series confers significant benefits. Looking at the world through binoculars progressively focused, we can easily convince us that there is a graduated series of quality focus, where each step della serie è un miglioramento rispetto al precedente. Se giriamo lentamente la manopola del colore di un televisore, ci convinciamo che c'è una serie graduale di miglioramenti progressivi dal bianco e nero alla visione a colori. Il diaframma dell'iride che apre e chiude la pupilla ci impedisce di essere accecati da una luce viva, mentre ci permette di vedere quando la luce è poca. Tutti sappiamo cosa si prova a non avere il diaframma dell'iride, quando siamo temporaneamente accecati dai fari di un'auto che sopraggiunge . Per quanto spiacevole e pericoloso possa essere quest'accecamento, non significa che l'intero occhio smetta di funzionare! L'affermazione che "l'occhio o funziona interamente o non funziona affatto" risulta essere not only false but obviously false to anyone for 2 seconds to reflect on this experience familiar.

Back to question 5. Considering each member of the X series that connect the eye to the absence of eyes, is plausible that each of them has worked well enough to help the survival and reproduction of such animals ? Now we have seen the stupidity anti-evolutionary assumption that the answer is "obviously not." But the answer is yes? And 'less obvious, but I think so. Not only is it clear that part of the eye is better than no eyes, but we can also find a number of credible eye structures intermediate between modern animals. This does not mean, of course, that these intermediaries represent truly modern ancestral types. But it shows that the intermediate structures are able to function.

(The series continues here on my new blog)