Monday, May 22, 2006

How do Irreducibly Complex Structures Evolve? Part Two

More of David Horton's article and my comments on it. The article can be accessed at:

David Horton:
Nor does the concept of 'irreducible complexity'. Complexity is always being reduced, modified, converted to a different kind of complexity, lost completely, made over again from a new starting point, throughout evolutionary history. The human body (and that of chimps, sheep ...) isn't an example of a perfectly designed machine, but a grab bag of bits and pieces put together over a long time. It far more resembles a sculpture made from junk than a Swiss watch.

[Bradford]: This is a story not an exposition explaining the evolution of irreducibly complex systems. Biochemical interactions are more intricate and precise than the Swiss watch. Proteins are molecular machines. Their amino acid components are encoded precisely by their genes both as to identity and sequence. Their expression is dependent on other proteins and DNA sequence patterns to ensure that expression is both timely and adaquate in quantity. Such proteins in turn have their own encoding genes. Yet protein synthesis would be impossible despite this level of organization were it not for dozens of different tRNAs, aminoacyl synthetases with multiple active sites, properly sequenced mRNAs, robosomes and timely infused energy in the form of ATP. Some effective antibiotics are based on the idea of disabling one of the the multiple components of this system. Proteins are not synthesized without this breathtakingly precise apparatus. These are precsion parts not a grab bag of junk. Horton, like others who make the same arguments, does not bother to account for how such an irreducibly complex system arose from a precellular environment. And for good reason. There is no evidence that it would.

If you take any organ in the body. ANY organ. And trace it back through evolutionary history you will see how it has evolved through more and sometimes less complex stages, ultimately back to the first multicellular species.

[Bradford]: Correction. You will not see how it evolved. Instead you will be shown other species in what is believed to be the same line of descent. You can then view the differences in an organ. No process of change is on display.

In many ways the big evolutionary jump was not from simple animals to complex ones but from single celled to multi-celled species (although even that may not have been such a big deal at the time - two cells which have failed to separate fully after division can potentially swim faster than any one cell, and so on).

[Bradford]: More stories which get less entertaining as we go on. The differences between prokaryotic cells and eukaryotic cells are enormous. One can start with the basics and compare their genomes to illustrate the point. References to two cells swimming together is a childish bedtime story not a scientific explanation.

Once you have a body with many cells, then the challenges of preventing water loss, moving, taking in oxygen, absorbing nutrients, getting rid off excess fluids and waste products, circulating oxygen and nutrients, responding to stimuli from outside the body, reproducing, can all be done in many different ways and combinations. And initially some of those ways will be quite simple - for example a straight gut with little difference from front to back, and later that gut will become longer and more coiled and with different functions along its length - more complex if you like. Both guts will function very well, and so will the intermediate stages. And this is not theory, we can see all those different ways in both the modern species and in the fossil record.

[Bradford]: Of course we see a variety of phenotype. What Horton and others avoid is pinning down evolutionary causes that can be traced to genetics. For example, where are explanations describing the evolution of nucleosomes and histone acetylation and deacetylation mechanisms? Then we might tie this in with timely transcription before proclaiming the evolution of eukaryotes a done deal.

And, finally, of course complex structures are made up of simple parts. The bodies of all multi cellular animals are made of many cells. All organs are made up of cells, in various combinations and functionalities. All cells are fundamentally the same, but can become specialised, and the combinations of specialised cells are what make up complex organs.

[Bradford]: Cellular differentiation illustrates more not less difficulties with standard evolutionary explanations.

All of that makes sense when evolution is the result of natural selection operating on mutations in a varied and changing environment.

[Bradford]: Another assertion without merit. Natural selection does not explain why or how the different components of the protein synthesis function would evolve nor how that would be related to environmental factors.

What doesn't make sense is that an intelligent designer would come up with a middle ear made from what were originally jaw bones, or an appendix, or an upright species with a back originally evolved for walking on all fours.

[Bradford]: Misconceptions getting in the way of good theology.


At 12:23 PM, Anonymous Anonymous said...

Maybe you could explain how cellular differentiation illustrates problems with evolution. What do you have in mind?



Post a Comment

Links to this post:

Create a Link

<< Home