Hunterleader109

I have a minor ciriticism. I am puzzled by Strickberger's explanation of how evolution can produce a complex structure by a succession of selective steps (Chapter 4, The Darwinian Impact: Evolution and Religion).

Note that once E has been drawn and survives, the chance of getting the EV combination is the 1/10 chance of drawing V and not the 1/100 chance of drawing EV together.

once 'EVOLUTIO' has been drawn and survives, the chance of getting the target word 'EVOLUTION' combination is the 1/10 chance of drawing N and not the 1/1000000000 chance of drawing EVOLUTION together.

The simulation experiment itself is clear. The problems start with the extrapolation to evolution:

1. total probability: Strickberger does not calculate the total probability of the string, he only states: there is a considerable chance of obtaining the word EVOLUTION. Well: that is a vague statement. What is the total probability? If we are not allowed to multiply the individual probabilities, must we add them? That would give 9/10. This method obviously leads to an absurdity: every word longer than 10 letters that could be produced would have a probability of more than 100%. The probability would become higher when the word is longer, which is also absurd. My intuition says that the probability should become lower. So I don't see how Strickberger could escape the conclusion that the total probability of the string in example-2 is also (1/10)⁹. As long as the frequencies of the letters in the bowl and the target sequence stay the same, the probability of arriving at the targetEVOLUTION is the same. It looks as if Strickberger proposes a system without memory: every new draw forgets about all the previous ones. Or does he want to say that the total probability is irrelevant, because each step has a reasonable chance (1/10)? Then it would be very easy indeed to create long protein chains.
2. biological: apparently what he wants to say with his example-2 is that intermediates (even the shorter ones) always have survival value. Otherwise his example-2 simply would not work. But he cannot assume this, this has to be shown by evidence. Intermediates can be neutral or disadvantageous. And I think Strickberger makes a highly unrealistic assumption. It is not true for highly conserved proteins like histone-4 (1), but could be true for myoglobin, alpha-, beta-, gamma-, delta- hemoglobins (p. 260-265).
3. biological: To establish the target EVOLUTION at each selection event 90% of individuals should not reproduce (or die without descendants), which is a very severe selection. This is unrealistic.
4. setup: the rules of the game. The initial condition of the bowl is ten different letters (there is an A included to allow words like EVOCATION and ELEVATION). This could be to simplify the calculation but also gives 'a reasonable probability' in each stage. When the bowl is set-up with all 26 letters the probability would decrease to 1/26. What matters of course is real life probabilities. Another simplification is the length of the target word EVOLUTION: small compared with the length of proteins (hundreds of amino acids).
5. illustration: the illustration of example-1 shows a handful of letters. But a handful of 9 letters is not a sequence of 9 letters. It only contains the right letters: 1 E, 1 V, 2 O, 1L , 1 U, 1 T, 1 I, 1 N. From these 9 letters 362880 9-letter combinations ('words') can be made (2). How can an ordered sequence be produced from a handful of unordered letters? The order can only be produced by drawing letters one by one. But in that case the difference with example-2 is not clear anymore. The difference is of course that in example-1 only the complete string of 9 letters is evaluated and if the word fails, all the 9 letters are put back in the bowl and the drawing starts from scratch.

Notes:

1. see for an explanation of the histone-4 case: Mathematics of Evolution by Fred Hoyle on this site.
2. that is the number of permutations of 9 objects: 9x8x7x6x5x4x3x2x1.
3. see for the importance of intermediates: review of Michael Behe on this site.
4. Michael Denton(1986), Hubert Yockey(1992), David Foster(1993), Dean Overman(1997), William Dembski(1999) (all reviewed on this site).
5. Douglas Futuyma (1998) Evolutionary Biology, Third edition.

Further Reading

• Monroe Strickberger is also the author of the textbook Genetics, 1985, 3d ed.
• The homesite of Strickberger's EVOLUTION by the publisher.
• Google books.
• The fourth edition of Strickberger is edited by Brian K. Hall, and Benedikt Hallgrímsson. (including Preview Chapter 1 and Chapter 3!)