At the end of this post about the Avida experiment -- a computer simulation of evolution that is claimed to demonstrate that random mutation and natural selection could generate great complexity -- I rhetorically asked Intelligent Design advocates what they had to say about it. I decided to e-mail that question directly to mathematician, philosopher, and ID maven William Dembski, author of The Design Revolution and other books on Intelligent Design, with whom I've had the pleasure of corresponding briefly. I asked him if there was a convincing rejoinder to the Avida experiment, and he responded with this link to an essay [in PDF] by Royal Truman (now there's a name!) of Mannheim, Germany.
It's arcane and densely mathematical and not for the fainthearted [UPDATE: a less substantive, but funnier, riposte is here], but the essence of it is that Avida produces the desired results because it has an intelligent designer(s), who has predisposed it to do so by what was selected to put in and by the characteristics of complex living organisms that were left out. A few key quotes: [by the way, if anyone could tell me how to highlight, copy and paste from PDF documents, I'd be most beholden.]
Neglect of key factors or unrealistic parameter settings permit conclusions to be claimed which merely reflect what the decision maker intended . . . We conclude that the simulations "work" because of several judicious assumptions and parameter settings which insure this outcome a priori . . .
Specific examples follow. The one that was easiest for me to understand was that the code for the "metabolic" functions that enable Avida's "digital organisms" to replicate was not made vulnerable to mutation, the way it would be in a living organism, where most random mutations would be deleterious or lethal -- "a fact subtle enough to escape the attention of many specialists":
The only thing mutating are short strings of symbols . . . and not any computer programs. The software shell actually or figuratively performing critical functions ("replicate your genome from here to there"; "generate metabolic energy"; etc.) are written in C++ and are neither coded for by the genome (unlike real organisms) nor subject to mutation. The rest of the infrastructure is provided for free in the form of computer technology (stacks, registers, electricity, cables, chips, etc.), unlike real cells in which physical ribosomes, cell walls, ATP and so on must be genetically coded, and thus in the Avida program cannot be damaged by mutations. . . . Over 99.9% of the indispensable coding material needed for a minimally sized real organism to survive has been shielded from the possibility of any kind of mutation.
Also, the "digitorgs" have been outfitted with smaller genomes and higher mutation rates than even the smallest, simplest real-world bacterium. And "[n]ovel functions are easy to attain, compared to living organisms, and these offer immediate, dramatic selection advantages." Truman's conclusion:
By generously rewarding instruction patterns which produce logic functions, the net effect of Avida type mutations over many runs is virtually guaranteed to ensure increased functional complexity over time . . . This is not some kind of law of nature, but an inevitable result of how the Avida system and runs are designed.
This is deeper into the guts of the Intelligent Design debate than most people care to go, deep beneath the emotions in the realm of science where the question, with all its moral and metaphysical repercussions, will ultimately have to be decided. Many thanks to Bill Dembski for keeping this blog on the front lines of the debate.