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The weasel program, Dawkins The thought experiment was formulated by Richard Dawkins, and the first simulation written by him; various other implementations of the program have been written by others. == Overview == In chapter 3 of his book ''The Blind Watchmaker'', Dawkins gave the following introduction to the program, referencing the well-known infinite monkey theorem: The scenario is staged to produce a string of gibberish letters, assuming that the selection of each letter in a sequence of 28 characters will be random. The number of possible combinations in this random sequence is 2728, or about 1040, so the probability that the monkey will produce a given sequence is extremely low. Any particular sequence of 28 characters could be selected as a "target" phrase, all equally as improbable as Dawkins's chosen target, "METHINKS IT IS LIKE A WEASEL". A computer program could be written to carry out the actions of Dawkins's hypothetical monkey, continuously generating combinations of 26 letters and spaces at high speed. Even at the rate of millions of combinations per second, it is unlikely, even given the entire lifetime of the universe to run, that the program would ever produce the phrase "METHINKS IT IS LIKE A WEASEL".〔For a string of 28 characters, with 27 possible characters (A-Z plus space), any randomly generated string has the probability one in 27^28 of being correct; that is approximately one in 10^40. If a program generating 10 million strings per second had been running since the start of the universe (around 14 billion years, or 10^17 seconds), it would have only generated around 10^24 strings by now.〕 Dawkins intends this example to illustrate a common misunderstanding of evolutionary change, i.e. that DNA sequences or organic compounds such as proteins are the result of atoms randomly combining to form more complex structures. In these types of computations, any sequence of amino acids in a protein will be extraordinarily improbable (this is known as Hoyle's fallacy). Rather, evolution proceeds by hill climbing, as in adaptive landscapes. Dawkins then goes on to show that a process of ''cumulative'' selection can take far fewer steps to reach any given target. In Dawkins's words: By repeating the procedure, a randomly generated sequence of 28 letters and spaces will be gradually changed each generation. The sequences progress through each generation: :Generation 01: WDLTMNLT DTJBKWIRZREZLMQCO P 〔Note: the 4th character of line 1 is missing in Dawkins' text; however line 2 suggests it was probably a T〕 :Generation 02: WDLTMNLT DTJBSWIRZREZLMQCO P :Generation 10: MDLDMNLS ITJISWHRZREZ MECS P :Generation 20: MELDINLS IT ISWPRKE Z WECSEL :Generation 30: METHINGS IT ISWLIKE B WECSEL :Generation 40: METHINKS IT IS LIKE I WEASEL :Generation 43: METHINKS IT IS LIKE A WEASEL Dawkins continues: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「weasel program」の詳細全文を読む スポンサード リンク
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