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Is Modularity a Pre-Requisite for Evolvability?

One of my favorite biologists is Gunter Wagner. He makes the claim in Genome Biology and Evolution that evolvability and modularity are highly associated. While not proof of a requirement, I think that Wagner is on the right track.

In fact, this sort of research can actually bridge the gap between Intelligent Design and Evolutionary biology.

The main critique ID has for evolutionary biology is that the haphazard mutation/selection paradigm does not create organisms. That doesn’t necessarily mean that they didn’t evolve in some way, but it does rule out the haphazard mechanisms.

As I pointed out in 2008, there is a difference between “parameterized” evolution and “open-ended” evolution. Parameterized evolution requires information about the most likely productive ways to evolve. It means that evolution happens in discrete units, not just in haphazard molecular alterations. A similar concept was developed in 2006 by Lynn Caporale called The Implicit Genome.

In any case, what all of these ideas and suggestions have in common is that information precedes evolution rather than arising out of it. If modularity enables evolvability, what happens before the modularity? Where did the modularity originally come from? This is the core of ID – that information and its similar entities are requirements of evolution, not products of it.

NOTE – I don’t claim that evolution can’t produce any information, only that the information that it does produce requires large amounts pre-existing information to already be there (see also here).

EDIT – I forgot to mention some interesting articles I found when looking through the links to this one on Google Scholar:

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3 Responses to Is Modularity a Pre-Requisite for Evolvability?

  1. I’m no biologist, so feel free to correct me. But a quick look at the linked document appears to reveal:
    1) An arbitrary (and novel) definition of Modularity.
    2) A similarly arbitrary definition of Evolvability.
    3) The standard assumption that evolution via common descent did occur, and that correlations between protein structures is therefore a result of evolution – see #2.

    I’d therefore propose that the factual result from the attached is that they have identified a particular form of structure to proteins that is shared by mammals at a higher incidence rate than the remainder of the proteins that doesn’t meet their structural definition.
    On the theoretical results, this is not evidence for evolution, but a theory of the path of evolution if it did occur. It does also appear to support the competing theory of common purpose = common design elements.

    I’m not entirely convinced of the “modularity”, however. Looking through the article and additional links, it appears that any structural formation that fits certain criteria, and appears in multiple proteins, is somewhat arbitrarily deemed “modular”. It’s not like DNA, where we appear to have Stop and Start codons that clearly delineate segments (modules?). Is there any functional or other support for deeming these structures “modular”? Is there empirical evidence for these “modules” being moved/shuffled/transferred/evolved? I know we, as human beings, love patterns, but does a pattern = module?
    (Not intended to be dismissive of the article – just wondering out loud).

  2. drc466 -

    You make some very excellent points. However, on #1, while it is a *novel* method of defining modularity, I don’t find it arbitrary. In fact, he makes a fairly good case for it in his Materials and Methods. Certainly, it is hard to make a direct mapping between the concept of modularity and its concrete implementation, I think Wagner makes a good step forward.

    I actually agree with you on #3. In evolutionary biology, I always wish that they would make comparisons across phylogenetic groupings – how is it the same or different as we look among subspecies? among species? genuses? families? orders? classes? phyla? This would make their work more relevant to a wider range of people. Perhaps that would be a good study for an ID’er to do – take data sets such as this one and compare it at different phylogenetic levels.

    As for modularity, there actually *is* empirical evidence for modularity. However, the evos usually focus on it because it goes against their belief in unguided mutations. If mutations are happening in a coordinated basis, along the lines of their modules, then it isn’t exactly haphazard – it is more planned.

    Anyway, I did a review of some of these mechanisms a while ago here. I’m sure there’s newer and even better stuff, but I haven’t had the time to stay on top of it.

    You also might be interested in a YouTube video I did a while ago on programmed mutations, and also a series I did here on the same subject.

    As a simple example, transposable elements can mobilize modules around the genome. They can create active sites for repeat expansion, and make other structural changes to genes.

    I think you are correct that Wagner did not prove his thesis, but I think the idea and discussion are interesting nonetheless.

    And, along those lines, I can’t believe I forgot to link to a classic ID paper on the subject: Origin of Insect Metamorphosis Based on Design-By-Contract.

  3. johnnyb,

    Thanks for the response and links – I too found the idea and discussion interesting.

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