As Neil Rickert was foolish enough to grant me posting rights, I had better take advantage of the offer before the sysops sensibly change their minds.
Consider an argument used consistently by the ID community: that the natural processes of genetic mutation and environmental selection acting upon the resultant variation are incapable of generating speciation.
Their recurring metaphor is of improbable islands of fitness separated by unbridgeable seas of non-functionality. Even if the hill-climbing capability of “random mutation plus natural selection” is real (and even incorporating unselected allele frequency changes), evolution can’t work because “you can’t get there from here”. For brevity, let me acronymise this argument as CANTSWIM.
CANTSWIM has a great many shortcomings as a metaphor for how evolutionary processes actually work, and you don’t need me to enumerate them. But let me hand over the title deeds to the evolutionary farm, and assume that CANTSWIM is factual.
At the same time, the ID community has adopted the claim made by the leadership of the ENCODE program that >80 per cent of the human genome is functional. The devil, of course, is in the detail of how “functional” is defined.
Let me leave aside whether ENCODE’s leadership or the ID people are using the term appropriately. In my opinion, if insertion of a random nucleotide sequence into a genome yields a bare biochemical response but no downstream effect on the phenotype, then that is prima facie evidence that the use of the term “functional” in this context is trivial.
However, let me go further and grant the whole house of functionality to the ID proponents. Let me grant that the vast majority of base sequences in the human genome are functional in the sense of directly determining the phenotype of an individual human being via protein expression or regulatory control. Let me dub this argument as CANTCURL.
Now, it seems to me that CANTCURL and CANTSWIM contradict each other.
If CANTCURL is true, then CANTSWIM must be invalid. That is to say, CANTCURL demands that virtually any change in a genome results in new functionality (by definition, since if they form part of the >80 per cent, new sequences must be functional, and at the same time “not previously present in the genome”).
Surely it follows that it is easy, simple, inevitable, a matter of natural course, to get to some new functional island from whatever atoll the organism happens to be sitting upon. All it takes is to wait a while and new functionality will arise, because CANTCURL guarantees that virtually any genomic configuration is functional. To wax metaphorical, the CANTSWIM sea must be shallow indeed.
Conversely, if CANTSWIM is true, then CANTCURL must be invalid. If the islands of functional phenotypes are truly separated by unbridgeable abyssals of impossible configurations, then how can functionality be present in virtually any nucleotide sequence?
I do not believe that the contradiction between CANTCURL and CANTSWIM is a purely one of logic or of definitional word games. Resolving the apparent contradiction is susceptible to experiment.
Certainly the truth value of CANTCURL can be tested by experiment (the mouse genomic excision experiment, for instance). Further experimentation on specific genome sequences should reveal whether their biochemical reactivity actually maps onto regulatory or protein expression, or is simply genomic noise.
CANTSWIM is more difficult to examine experimentally, because its underlying assumptions about the structure and temporal stability of “fitness landscapes” are so poorly defined.
For example, the overall “fitness landscape” of an organism must surely be some vastly multidimensional aggregation of simpler fitness “landscapes” derivable for every individual genetic locus that is expressed in its phenotype.
How does one aggregate the antelope fitness landscape for escape speed with the fitness landscape for resistance to tsetse fly with the fitness landscape for digestion efficiency?
Even so, what we do know is that experiments such as Lenski’s longitudinal series demonstrate that CANTSWIM cannot possibly be universally true.
My purpose in posting this is to invite comment on whether this apparent contradiction in the ID argumentation is real, or am I simply misunderstanding what they are claiming. All comments and abuse welcome.
Apologies to the Painted Jaguar.