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Author
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Topic: IC-based predictions
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rafe gutman
Member
Member # 134
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posted 28. August 2003 23:03
i brought this issue up about a year ago, but it failed to develop any serious discussion. i think it's an important issue, so i'm bringing it up again.
using behe's original definition, an irreducibly complex system is one that possesses a core of multiple parts, all of which are essential to the system's function. it has been argued by behe and others that because the system requires multiple parts to function, that these parts must assemble all at once, and therefore could not have evolved gradually. if this is in fact, true, then there are some predictions we might make regarding IC systems.
first of all, if we identify an IC system composed of say, 10 parts, then we should find all 10 of these parts (or homologues) in any organism that possesses at least one of the parts. however, IDists would be quick to mention, and rightfully so, that evolution can co-opt parts from an IC system for other functions. the example of the simpler type 3 secretory system evolving from the IC bacterial flagellum immediately springs to mind. this means that if we identify an organism that possesses one or more parts, but not all ten, then we can predict that this system evolved from the original IC system (and not vice versa). i think a phylogenetic analysis of the parts from the different organisms could verify this prediction.
so the issue is, can we use IC to make predictions of this nature? i don't see why not. however, i don't think a single confirmation would be enough to vindicate IDists, because of course non-intelligent evolution can also explain the origin of simpler systems from more complex ones. but if this prediction were made repeatedly, and confirmed repeatedly, then would this constitute evidence for ID? personally, i'm not sure, but it would raise some eyebrows.
[ 28. August 2003, 23:05: Message edited by: rafe gutman ]
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Rex Kerr
Member
Member # 632
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posted 29. August 2003 16:40
That's an interesting idea, but experiments are most useul when they discriminate between competing hypotheses. Unfortunately, I'm not sure I know what to predict about the expected distribution of systems identified as IC under an evolutionary model of creation of apparently IC systems.
One thing that is clear is that components that are essential in one organism are not in another. For instance, signalling pathways can be thought of IC systems, as they consist of a cascade of multiple proteins, each signaling to the next, with the final targets having some biological relevance. However, there is evidence that the "IC core" is different in closely related organisms (e.g. in the differentiation of the egg-laying machinery of C. elegans vs. that of similar nematode worms). Likewise, different flagellar components are dispensible in different organisms. The first two components of the blood clotting cascade aren't necessary in lamprey, etc..
It seems to me as though this might complicate your analysis, first since it makes it more difficult to figure out what is IC, and second because there exists at least some data that is directly contrary to your hypothesis. (I.e. lamprey blood-clotting requires fewer components than that of other vertebrates, yet the lamprey subset is the most widely shared.)
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