Field of Science

Evolution is no more unlikely than development

Here is an excellent argument why the fact that we do not yet understand how something really complex evolved is not a good argument that it did not evolve.

If you argue that it's very, very unlikely for complex biological structure to originate by evolution, then it is similarly very, very unlikely that the same complex structure can develop from a single cell.

Development is a most amazing process, and Dr. Louis' argument is that the only difference in believing that something as complex as the bacterial flagellum can develop vs. believing that it could evolve, is that we can actually see that it can develop, while we don't get to see it evolve.

Flagellum develops in bacteria all the time, as we speak, but it already evolved, so we don't get to verify that directly. And yet, suppose we were not able to see it develop over and over, then we should consider it just as unlikely that it develops by natural processes, as some people consider it unlikely that it evolved by natural processes.

If you are into the more theological aspects of this discussion, I suggest you go to BioLogos to get your fix, you freaking junkie.


  1. Bjørn, I fail to see the logic here. Why should the fact that one (on the face of it) unlikely thing actually happens make it less unlikely that another (relatively unrelated) thing could happen? Evolution and development are quite different and distinct processes, so a demonstration that development works (apparently without supernatural input) does not, as far as I can see, tell us much about evolution.

    The problem is, that the "argument" that evolution is very unlikely is an argument from stupidity (argumentum ad ignorantiam) - and how do you explain that to stupid (ignorant) people?

  2. There is a particular argument about probabilities of structures evolving by chance. Naîvely (i.e. not including all the evolutionary processes we understand), it gives a very low probability, prompting creationists to conclude it could never have happened.

    While the processes of evolution and development are very different, developmental processes are also quite amazing (i.e. seems designed), and Louis' argument is that if we didn't know what they were, then a similar probability calculation would give a very, very low probability that the flagellum could form developmentally. The crucial difference is that we can see flagellum develop in real time, so there is no point whatsoever to dispute that it does.


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