https://en.wikipedia.org/wiki/Weasel_program
In chapter 3 of his book The Blind Watchmaker, biologist Richard Dawkins gave the following introduction to the program, referencing the well-known infinite monkey theorem.*
I don't know who it was first pointed out that, given enough time, a monkey bashing away at random on a typewriter could produce all the works of Shakespeare. The operative phrase is, of course, given enough time. Let us limit the task facing our monkey somewhat. Suppose that he has to produce, not the complete works of Shakespeare but just the short sentence 'Methinks it is like a weasel', and we shall make it relatively easy by giving him a typewriter with a restricted keyboard, one with just the 26 (capital) letters, and a space bar. How long will he take to write this one little sentence?
[NOTE: How lazy of Richard Dawkins to fail to look up the author of his monkey business. It was Sir Arthur Eddington.
In 1928, British astrophysicist Arthur Eddington presented a classical illustration of chance in his book, The Nature of the Physical World: “If I let my fingers wander idly over the keys of a typewriter it might happen that my screed made an intelligible sentence. If an army of monkeys were strumming on typewriters they might write all the books in the British Museum.”
This is nonsense compounding nonsense. And yet my high school math teacher presented this proposition to his classes in the 1960’s.
First, an “army of monkeys” wouldn’t be very interested in hitting typewriter keys repeatedly. There is nothing for them to gain in so doing.
Second, those who did hit the keys would quickly get to the end of the line, and have no concept of returning the carriage to type the second line.
Third, those very few who somehow overcame the first and second hurdles, repeatedly, would find that the paper was ejected from the carriage, and they are hopelessly unable to replace the first page with a fresh sheet of paper.
Fourth, we will never get to the fourth problem of exhausting the ink in the typewriter ribbons because the “army of monkeys” would have defecated on or otherwise ruined every typewriter.
Fifth, Sir Arthur Eddington never began to consider the statistics of monkeys “selecting” 1 out of approximately 100 different keys, counting upper and lower case of all letters, numbers, and punctuation marks. A page of an average book has 250 – 300 words. (https://hotghostwriter.com/blogs/blog/novel-length-how-long-is-long-enough)
*Finally, the largest army in the world is the People’s Liberation Army of Communist China, with over 2,000,000 troops. This is hardly “infinite” in number. (https://economictimes.indiatimes.com/)
The average word has 6.47 letters. (https://capitalizemytitle.com/character-count/100-characters/)
Using the lower value of 250 words, times 6.47 letters equals 1,617 characters in a page.
1/100 to the 1,617th power is 10 to the -3,234, for just one page, much less “all the books in the British Museum.”
“we just think of one chance in 10 to the 40th power” as “impossible”. – Richard Dawkins, (The Blind Watchmaker, page 142)
Emil Borel, a famous statistician, defined “impossible” as an event with a probability of 10 to the -50 or less.*1
https://owlcation.com/stem/Borels-Law-of-Probability
There are 100 such marbles per meter, and 100 times 1,000 per kilometer.
Therefore 10 to the 5 marbles cubed equals 10 to the 15 marbles per cubic kilometer.
*1 https://owlcation.com/stem/Borels-Law-of-Probability


This is equivalent to finding one unique marble, in 923,400 billion billion spheres the size of earth, all full of identical marbles except for one, on your first and only attempt. You do not get an infinite number of attempts, not even two.

Calculations: (10 to the 5th marbles/km) cubed = 10 to the 15th marbles per cubic km
10 to the 15th marbles/cubic km x 1.083 x 10 to the 12th cubic kilometers/earth =1.083 x 10 to the 27th marbles to fill one earth sphere the size of earth.

10 to the 50th marbles / 1.083 x 10 to the 27th marbles/earth size sphere = 9.234 x 1023 earths full of marbles, which is to say 923,400,000,000,000,000,000,000 (923,400 billion billion) earths full to search and find the unique marble on your first and only try. Personally, I would call it impossible to find that unique marble in just one earth-sized sphere full of them.]



Dawkins then goes on to show that a process of cumulative selection can take far fewer steps to reach any given target. In Dawkins' words:
We again use our computer monkey, but with a crucial difference in its program. It again begins by choosing a random sequence of 28 letters, just as before ... it duplicates it repeatedly, but with a certain chance of random error – 'mutation' – in the copying. The computer examines the mutant nonsense phrases, the 'progeny' of the original phrase, and chooses the one which, however slightly, most resembles the target phrase, METHINKS IT IS LIKE A WEASEL.
Generation 01: WDLTMNLT DTJBKWIRZREZLMQCO P [2]
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:
The exact time taken by the computer to reach the target doesn't matter. If you want to know, it completed the whole exercise for me, the first time, while I was out to lunch. It took about half an hour. (Computer enthusiasts may think this unduly slow. The reason is that the program was written in BASIC, a sort of computer baby-talk. When I rewrote it in Pascal, it took 11 seconds.) Computers are a bit faster at this kind of thing than monkeys, but the difference really isn't significant. What matters is the difference between the time taken by cumulative selection, and the time which the same computer, working flat out at the same rate, would take to reach the target phrase if it were forced to use the other procedure of single-step selection: about a million million million million million years. This is more than a million million million times as long as the universe has so far existed.

[So much for Dawkins’ specious argument in defense of Darwinism, which he proudly claimed, “… made it possible to be an intellectually fulfilled atheist.” (http://UncommonDescent.com) Twenty-six capital letters plus the space bar equals twenty-seven. Twenty-seven to the twenty-eighth power equals ten to the fortieth different possible combinations, Dawkins’ definition of “impossible.” We are looking for only one of this “impossible” number. This is not for all of Shakespeare’s works, but for one short sentence, and even then, on a dramatically altered keyboard, not of fifty possible keys, lower case, and fifty more keys, upper case, but for only twenty-six keys, all upper case.

Of critical but neglected importance is the fact that for “selection” to occur, the intermediary produced by the random mutation MUST confer a “selective advantage” for the host organism, otherwise it will be lost. It is therefore incumbent on the advocate for Darwinism to demonstrate, in each case, what that improvement is and how it operates, every single time, without exception. “Selection” requires no less. This is easily done when copying short sentences, but not so easily done when originally constructing over 20,000 proteins in humans*a, the largest of which is titin, at 38,138*b amino acid residues in length.
One out of 20 amino acids “selected” consecutively 38,138 times has a probability of 1 chance in 10 to the 49,618. This is for only one protein. Calculating for chirality, i.e. the “selection” of L amino acids instead of D amino acids*c and all peptide bonds rather than the equally probable non-peptide bonds*d reduces the probability of original naturalistic synthesis to 1 chance in 10 to the 72,578. Twenty thousand more proteins to go!
*a - https://www.omim.org/entry/188840\
*b - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4889822/
*c - ½ to the 38,138 = 10 to the -11,480
*d - ½ to the 38,138 = 10 to the -11,480 ]


[Postnote: Richard Dawkins asserts, “We shall make it relatively easy by giving him (the monkey) a typewriter with a restricted keyboard, only 26 keys…”
The standard American typewriter keyboard has 88 keys, not 26.]