Richard Dawkins:

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Dawkins' classic was a passionate defense of Darwinism at a time when (in America) Darwinism was still often misunderstood and even opposed. Dawkins correctly emphasizes that Darwin's theory was no so much about evolving animals as about the emergence of complexity. Living beings are complex beings. Darwin explained where their complexity comes from. Therefore, Darwin showed that there is a way to design complexity without a designer: it is called "natural selection". Given enough time, natural selection can produce amazing complexity. The title of the book refers to a treatise by William Paley that emphasized how any watch has a watchmaker (therefore, claimed the British theologian William Paley, living beings, who are very complex watches, require the existence of the greatest of all watchmakers, God). Dawkins shows how natural selection works as the watchmaker, except that it is a "blind" watchmaker, because it has no sense of purpose. Design "happens", rather than being planned ahead by a designer.
In writing this book, Dawkins had obviously a target, the main objection against Darwinism: how is it possible that complex organisms "evolved", if their parts must be present all at the same time for the organism to work properly? An eye without the retina is not much use. Even an eye with a retina but without the proper connection to the brain is not much use. All these things have to evolve at the same time in order for an organism to be able to see, or eat, or walk. It seems impossible that by chance alone something as complex as a living organism would be created. While Dawkins' argument is not conclusive (so much so that even some biologists still believe that Darwinian theory is incomplete), he does an admirable job of explaining how accumulating small change can generate big change. An eye cannot arise suddenly from an eye at all (the odds are on in billions), but an eye can arise from something slightly different from an eye. And this "something" can arise from something slightly different from itself, and so forth. And that's how the eye. This sounds a whole lot more plausible, although Dawkins downplays a couple of points: 1. at each step of the "arising" a stable system must be generated ("stable" as in "capable of surviving and reproducing"); and 2. that system must survive long enough to reproduce, otherwise there would be no further evolution. In order for "homo sapiens" to arise, billions of small evolutions must have occurred in all of our organs. They must have occurred and occurred in such a way to satisfy the previous requirements. The odds are indeed very low. It is debatable whether there has been enough time (i.e., if two billions of years are enough) for these very low odds to actually occur. As a matter of fact, a number of biologists are searching for the "accelerator" that may explain how evolution of such complex organisms can occur in such a "short" time and with such efficiency.
Dawkins correctly answers the objection with the simple argument that even the most sophisticated organ is far from being perfect. We perceive only a fraction of the world. Our eyes don't see and our ears don't hear most of what is out there. Even the animals with the sharpest senses miss some frequencies. We are easily fooled by a sound or a picture. In other words, we "think" that we are such admirable beings, but the truth is that we are precisely one of those imperfect, partial realizations that we see as unlikely. Dawkins points out that numerous "innovations" were forgotten by nature just because they did not get transmitted. Our organs, far from being the best possible of each kind, are merely what survived of what arose. And, in general, Dawkins is terrific in embarassing anti-Darwinists by quoting their own words and proving how pathetic they sound when compared with the facts. Dawkins correctly repeats that their objects, far from being scientific, are simply an expression of "personal incredulity".
The difference between Dawkins and the anti-Darwinists is simply that Dawkins does know the animals he talks about. Whereas anti-Darwinists often simply write "I can't believe this", Dawkins can show that each and every occurrence of "impossible" evolution is instead possible (we can argue how likely, but definitely possible). Dawkins is also good at finding reasons why some features evolved over others. It may not seem obvious that polar bears should be white to camouflage in the ice, since they have no predators; but when one thinks that bears need to eat and that their preys run away when they see a big, fierce animal approaching at high speed, it makes a lot of sense that only white bears would survive in the white landscape of the pole: any bear of a different color simply starved to death!
Dawkins' description of natural selection is awesome. Dawkins likes to compare it with sculpting: the sculptor does not add anything to the marble stone, she actually takes away pieces of it. If you only read the sentence and do not see a sculptor at work, it sounds like a negative action, that destroys and certainly not creates. Instead, by taking away pieces of marble, the sculptor is turning a rough stone into a beautiful image. What sounds negative has actually positive effects. The same argument applies to natural selection, that is often conceived as merely destructive while it actually helps create all the living beings on this planet.
Natural selection is about interaction with the environment: basically, natural selection rewards who can best cope with the environment. One can view this interaction at the body level or at the gene level. Dawkins thinks the right level is the gene level (it is genes, not bodies, that struggle to survive). Genes' survival is determined by their interaction with the environment. Dawkins points out that the "environment" is also made of other genes: in some cases genes have to cooperate (and the genes that are best at cooperating are therefore rewarded) and in some cases genes have to compete (and the genes that are best at competing are therefore rewarded). Again, one can view the same argument at the body level: animals (or plants) need to cooperate and to compete in order to survive. But Dawkins believes that genes are the level at which natural selection operates. Needless to say, an additional complication is that the "environment" (including partners and competitors) change all the time.
Dawkins also illustrates Cairns-Smith's theory that self-replication originated in clay-crystals. According to this theory, RNA came before DNA, and it was originally simply a passive element, but then eventually took over the self-replicating chore because it was more efficient than crystals. And then evolved into today's DNA code. One of Dawkins' most durable contributions to his age is to have abstracted this idea. A replicator needs to build a survival machine for itself (the body). Indirectly, that survival machine opens new possibilities for self-replications, just like accidentally crystals invented a more efficient kind of self-replicator, RNA. Dawkins thinks that we are not on the verge of a new genetic takeover, whereby "memes" will replace "genes" as the main self-replicating device. Memes are patterns of information. Their survival machines are brains, or, better, minds (Dawkins does not rule out that, for example, computers could act as survival machines for memes).
Dawkins briefly touches on sexual selection. In the 1980s, Russell Lande advanced his theory of sexual selection. Lande thinks that sexual selection is a form of "positive feedback", whereby features that attract other sex tend to increase and, at the same time, the preference for those features in the other sex also tends to increase. The offspring of the mating caused by those preferences is likely to inherit the same preference and the loop continues at ever increasing speed. The result is exponential increase in the "sexy" feature, whether a tail or a sound.
Dawkins shows how Gould's punctuated equilibrium (often depicted as an objection to Darwin's theory) lies firmly within Darwinian territory and offers his own, devastating, refutation of Lamarckism.
Dawkins also clarifies the meaning of "random" in Darwinian biology: mutations are not "random" in the mathematical sense of the word (that anything is possible) since there are at least chemical constraints. They are not even random in the physical sense of the word (that no external force can affect them) since radiations can sometimes cause mutation. They are random in the sense that they have no other purpose than to mutate; they do not necessarily improve the organism or the organism's chances of survival. "Chance" is probably a better word.
It is intriguing that Dawkins finds analogies between the evolution of biological systems and the evolution of artificial systems: the theory of radar vision and the theory of bats' ecolocation developed in parallel, unaware one of the results of the other, and eventually formulated the same computational model.
All in all, Dawkins' is the ultimate introduction to Darwinism. In his preface, Dawkins makes an interesting point: scores of distinguished philosophers and scientists, from Aristotle to Newton, missed the point. We had to wait until the 19th century AD, until Wallace and Darwin, to discover this fundamental law of nature that now appears so obvious. It was easier to figure out the motion of planets (things that we can hardly see) than the origins of species.

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