Irreducible complexity
From CreationWiki, the encyclopedia of creation science
Irreducibly complexity (IC) is a conceptual test for intelligently designed components or system. It is asserted that if a system cannot be reduced to fewer components and retain functionality, then it could not have evolved by the gradual assemblage of components over successive generations.
The concept was popularized by Lehigh University biochemist Michael Behe in his 1996 book Darwin's Black Box. Intelligent design theorists argue that while some systems and organs can be explained by evolution, those that are irreducibly complex must have been assembled by an agent of intelligence.
There are many examples of molecular machines, such as the bacterial flagellum, that are composed of numerous elements. Behe rightly points out that such machines are irreducibly complex in that if any one part were removed, the function in question would be instantly lost. How then could such a machine be built up gradually if it will not work to any selectable degree until all its parts are present in their proper order?
| “ | Michael Behe describes irreducible complexity as "a single system which is composed of several interacting parts that contribute to the basic function, and where the removal of any one of the parts causes the system to effectively cease functioning. An irreducibly complex system cannot be produced gradually by slight, successive modifications of a precursor system, since any precursor to an irreducibly complex system is by definition nonfunctional. Since natural selection requires a function to select, an irreducibly complex biological system, if there is such a thing, would have to arise as an integrated unit for natural selection to have anything to act on. It is almost universally conceded that such a sudden event would be irreconcilable with the gradualism Darwin envisioned. At this point, however, 'irreducibly complex' is just a term, whose power resides mostly in its definition. We must now ask if any real thing is in fact irreducibly complex, and, if so, then are any irreducibly complex things also biological systems."[1] | ” |
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Cooption
Kenneth Miller, a well-known evolutionary biologist from Brown University, points out that certain subsystems of the bacterial flagellum would still be in working order if other parts were removed. The overall flagellar motility system requires around 50 different types of proteins (and underlying genes to code for them). However, it is quite interesting to note that 10 of these genes and the resulting structure within the flagellar motility system also code for what is known as a type III secretory system (TTSS). The TTSS is used as a toxin injector by some especially nasty bacteria that attack both animals and plants. Therefore, Kenneth Miller argues that it is mistaken to use the flagellar system as an example of a truly irreducibly complex machine since around 40 different parts could be removed from the machine without a complete loss of function. Miller also points out that the majority of the protein parts of the flagellar system have other functions as parts of other systems within bacteria.[2]
What now? Has Miller disproved Behe's notion of irreducible complexity? It sure seems like he has - at first glance anyway. However, what Miller seemingly fails to consider is that the function of flagellar motility is still irreducibly complex regardless of other subsystems functions are or are not maintained with various flagellar system reductions. Without a sizable number of specifically arranged protein parts the function of flagellar motility cannot exist. In fact, all systems of function are irreducibly complex. It doesn't matter if subsystem function is maintained. This is like arguing that the motility function of an automobile is not irreducibly complex because the lights still work even if the engine or tires or drive shaft are removed.
But, what about Miller's notion that the working subsystems can be easily added together to form functions with greater and greater minimum structural threshold requirements? This notion is in fact true up to a point. There are many examples of low-level evolution in action. Miller himself points out a few of these in his book, Finding Darwin's God, to include an experiment by Barry Hall. Hall's experiment is in fact very interesting. What Hall did was delete the genes in a type of bacteria called E. coli that produce a protein enzyme called lactase. Without this lactase enzyme the bacteria could no longer digest the sugar lactose for energy. Hall wondered if these bacteria, if grown in a lactose-rich environment, would evolve the lactase function back again using some other aspect of their gene pool. And, they did! In just a few generations (probably a single generation) the colony of a few billion bacteria evolved a brand new lactase enzyme with just a single point mutation to another gene. This gene product did not have the lactase function before. So, this would seem to be real evolution of a novel function in observable time.
Of course, this is where Miller's descriptions of Hall's experiments end. However, what Hall did next is most interesting. Hall wondered what would happen if he deleted the newly evolved lactase gene. Would the bacteria evolve yet another novel lactase enzyme? Hall carried out this experiment and observed the bacteria for over 40,000 generations - - and they didn't evolve another lactase enzyme despite a very high mutation rate in a large population living in a highly selective environment. Frustrated, Hall referred to this colony as having "limited evolutionary potential".[3]
Now, what is it that limited the evolutionary potential of Hall's bacteria? How is it that such a relatively simply function could not be found by random mutation and function-based selection many times in such a large colony living in such a highly selective environment?
The answer, is found in the expansion of non-beneficial gaps between potentially beneficial genetic sequences as one considers functions with greater and greater minimum structural threshold requirements. As it turns out, evolution proceeds quite easily and very rapidly when it comes to functional systems that only require very few structural threshold requirements or a loss of a pre-existing system of interaction (most forms of antibiotic resistance). Occasionally evolutionary mechanisms produce higher level functions where a few hundred loosely specified amino acid residues are required (lactase, nylonase, etc). However, there are no observable examples of evolution in action produce any novel system of function that requires over 1,000 specifically arranged amino acid residues working together at the same time. There's not one example of evolution beyond this level in all of scientific literature - not one example.[4]
Now, consider that the flagellar motility system requires around 10,000 fairly specifically arranged amino acid residues all working together at the same time. The next closest beneficial "steppingstone" subsystem function is not remotely close at this level of functional complexity. Even if two such subsystems could be put together to make the flagellar system, the odds that only a few residue changes would be required are extremely poor. More likely many dozens of residue changes would be required. The odds of having the needed amino acid residue changes present in one bacteria within a huge population at the same time are extremely remote this side of trillions upon trillions of years of time. Such gaps may not seem like much at first glance, but when considered more closely, the odds of their being crossed in what anyone would consider a reasonable amount of time are pretty much impossible.
In this light, consider that the TTSS system is now thought to have evolved from the fully formed flagellum - not the other way around. In 2000, Nguyen et. al. published a paper in Journal of Molecular Microbiology and Biotechnology titled, Phylogenetic analyses of the constituents of Type III protein secretion systems[5] In this paper the authors argue strongly that the TTSS system evolved from the flagellum. Of course, those like Miller fail to point out such conclusions published in mainstream scientific literature. But such conclusions should have been obvious from the beginning. Which came first? - - a cavefish without eyes or a fish in a pond with eyes? Clearly it is much easier to loose something that was already there than it is to create it in the first place. Remember Humpty Dumpty and all the kings men?
| “ | In The Origin of Species Charles Darwin stated: "If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down." | ” |
Related References
- ↑ Molecular Machines: Experimental Support for the Design Inference by Michael Behe
- ↑ The Evolution of the Flagellum by Dr. Sean D. Pitman May, 2006.
- ↑ Limited Evolutionary Potential Sean D. Pitman M.D. 2006. November 2006.
- ↑ The Steppingstone Problem: And the Limits of Evolutionary Potential by Sean D. Pitman, M.D. March 2004.
- ↑ Phylogenetic analyses of the constituents of Type III protein secretion systems. J Mol Microbiol Biotechnol. 2 (2), 125-144, 2000.
Related links
- Evidence for Intelligent Design from Biochemistry by Dr. Michael Behe
- Irreducible Complexity Revisited by William Dembski
- Argument: ‘Irreducible complexity’ by Jonathan Sarfati
- Evolving the Irreducible: Behe's Mousetrap Problem by Sean D. Pitman M.D.
