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Evolution and the Brain

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LE CRÉATIONNISME EST-IL SCIENTIFIQUEMENT RECEVABLE ?Creationism vs Evolution'Intelligent Design Creationism and Its Critics': Supernatural SelectionBook : The Blind Watchmaker, by Richard Dawkins, 1986
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To understand the origin of the theory of intelligent design, we must go back to 1802 and English theologian William Paley's famous analogy of the watchmaker. In Paley's words, if you are walking along a beach and you find a watch in the sand, you immediately infer that the watch is the product not of a natural process, but rather of the skill and expertise of a watchmaker.

Until 1859, this argument had the majority of people convinced that nature in all its complexity must indeed have been created by some kind of a god. But that year, Darwin published The Origin of Species. This book brought together so many observations supporting the principle of natural selection as the main engine of evolution that it persuaded the scientific community.

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“Intelligent design" is the most recent and sophisticated form of creationism.

The adherents of intelligent design don't believe in an Earth that is only 10 000 years old, nor in the other literal interpretations of the Bible. But they do assert that science should be open to certain supernatural explanations for the existence of life, and they would like to see this option taught in the schools.

One of the main arguments offered in favour of intelligent design is that of “irreducible complexity”. Something is said to be irreducibly complex when the slightest component cannot be removed from it without its immediately ceasing to function.

The mousetrap is an oft-cited example of an irreducibly complex object. If you take away even the tiniest part of a mousetrap, it stops working. This irreducible complexity of the mousetrap is taken as proof that it is the product of an intelligent design, that of the engineer who drew up the plans for it.  

In contrast, living organisms that are the product of evolution were formed without any pre-established plan, from the “primordial molecular soup", through nothing more than the interaction of chance with the various elementary forces of physics.

But the advocates of intelligent design, such as Michael Behe, refuse to accept this construct of evolution. They say that a living being, and in particular its cellular machinery, is too complex to have been manufactured by natural selection. In fact, they consider it a case of irreducible complexity and hence believe that we must admit the existence of an “"intelligent designer"”somewhere who designed this living machinery.

Like conventional creationists, however, the advocates of intelligent design seem either not to know or deliberately to ignore certain basic facts of biology, in particular the high degree of redundancy among the genes involved in identical or similar functions. Far from being an example of waste, this redundancy allows mutations to create genetic variability without compromising the overall functioning of the organism. Moreover, many studies have shown how some proteins that originally evolved to perform one function can undergo “exaptations” that enable them to fulfil another.

These observations alone cast serious doubt on the supposed irreducible complexity of life. Modifying or removing one element from the structure of life, far from making it collapse, instead produces the diversity that can potentially enable it to grow still more complex.

The fact that there are many molecular mechanisms that we do not understand and cannot yet explain by an evolutionary process in no way invalidates the theory of evolution. It may highlight the limitations of our current knowledge, but it certainly does not constitute a proof of irreducible complexity or, as a corollary, an omniscient creator.

The human eye is a complex structure if there ever was one. Believers in intelligent design often cite it as an example of an irreducibly complex organ. But biologists are now familiar with several examples of intermediate forms of the eye, and also have much evidence that this special structure has evolved independently several times since life began. For example, the eye of an octopus shows much similarity to the human eye, even though the octopus comes from a completely different genetic line and its eye has much more limited capabilities. Thus, in response to the classic creationist taunt, “"What good is half an eye?, the best comeback is... It's better than no eye at all".

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