Historical Contingency Proven in Labs, then Behe blathers.

June 10, 2008 | By | 10 Replies More

In brief, Stephen Jay Gould proposed the idea that evolution is truly stochastic (a particular technical kind of random), that if we started evolution over as of a million years ago, we probably wouldn’t be here in our current form. That is, any evolutionary step is contingent on the history of steps that went before, each based on a combination of random mutation and environment.

I’ve read several posts about the new discovery today, and the best summary with accurate excerpts and clear analysis is this one from Pharyngula (PZ Meyers Myers).

In brief: A single experiment ran over 20 years, or 33,000 generations of bacterial cultures, where they froze a sample every 500 generations from each of 20 separate populations, all nurtured identically over the entire time with a particular set of stressful conditions. When a particular beneficial change occurred to the population, they could track back genetically and see what the genetic change was, and what probably allowed it to manifest in a visible way. Then they tried to get the same thing to happen again starting from various suspected branching points. In some cases, the same mutation happened again.

Of course, Michael Behe of the Discovery Institute quickly posted a sort of rebuttal to the idea that yet another piece of evolutionary theory has been proven, so Meyers took him to task. Behe claims that the experiment proves how incredibly unlikely such changes are, and therefore they need an Intelligent Designer to guide them. Apparently he missed the point that the complex series of changes did happen, and were repeatable, but only in a statistical manner. As opposed to in a pre-ordained, designed sort of way.

Or possibly his point is that God individually guides the evolution of laboratory E. Coli to fool scientists into thinking that supernatural intervention is unnecessary. It’s hard to tell.

[Admin note:  here is the description of the experiment by New Scientist]

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Category: Current Events, Evolution, History, ignorance, Religion, Science

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  1. Erich Vieth says:

    I'm surprised that evolutionary biologists still pay any attention to Michael Behe. He's like the Ann Coulter of EB–outrageously wrong all too often. I don't get it, except, perhaps he serves as a fairly steady baseline for measuring true progress.

    This was a terrific experiment and you have to admire the extent to which it traced evolution for such an incredibly long period of time. But I'm also fuzzy on whether this result truly disproves S.J. Gould. I'm assuming that Gould made a strong claim that what happened in the experiment wouldn't happen–or am I misreading Gould?

  2. Dan Klarmann says:

    Behe reminds us that flogging the scientifically dead horse of Intelligent Design continues to draw attention, and still encourages many people to bet on it as it rots on the field.

    This experiment vindicates Gould, not disproves. There is only a statistical chance of evolution following any particular path given identical germ material and conditions. But any step is contingent on certain other steps having been followed before, ie: Historical Contingency. That was Gould's conjecture; his hypothesis. Now demonstrated conclusively.

  3. Ben says:

    Anti-spam word is "Dan". 🙂

    Anyway, PZ is very particular about the spelling of his name… Myers Myers Myers

  4. Erich Vieth says:

    Dan: Perhaps you can sense my confusion. After all, the study shows that is a statistical chance of following a particular path, but contingency upon the occurrence of other steps occurring. The question, then, is where to put the emphasis: the path or the contingency. It seems like it would be a continuum, with simpler organisms being more predictable, with Gould being more correct when it comes to more complex life forms. Is this how you read the study?

  5. Dan Klarmann says:

    The degree of complexity is not predictable, nor an indicator of superiority. An amoeba has dozens of times more DNA than does a human; much more complex.

    The exact direction that a population will take is not predictable. However, the central tendency of the potential directions of a population given known starting conditions is predictable, within the rules of chaos theory.

    Of the 20 strains in the experiment, one developed the two particular precursors that had no evolutionary advantage which, in turn allowed the mutation that provided an advantage to occur. Given the first 2, the third became likely. That third change may well have happened in other populations, but without the precursors, it conveyed no advantage, and therefore was not expressed.

    Because the first two gave no advantage, it took about 30,000 generations to have those first two available in one population when the change that conferred the advantage happened. The advantaged genes then propagated more vigorously and became obvious, expressed. They restarted cultures from the saved generation in which that pair occurred, and ran that culture forward a number of times. Sometimes, the advantage then occurred again. Not always.

  6. Dan Klarmann says:

    Thx Ben. Now I see how an extra "E" changed a winner to a wiener,

  7. Dan Klarmann says:

    Here's another look at this study and it's detractors from AiGBusted

  8. Dan Klarmann says:

    Here is posted a great set of responses by the researcher/author to attacks from Conservapedia (an anti-science wiki by Phyllis Schalfly's kid): All time classic creationist pwnage

  9. Erich Vieth says:

    And here's the link directly to Conservapedia. This exchange between the voice of fundamentalism (Conservapedia) and the voice of science and reason (Lenski) should not be missed. Lenski shows more than a reasonable amount of patience with the oafs, at least for awhile. http://www.conservapedia.com/Conservapedia:Lenski

  10. Dan Klarmann says:

    I linked to it on BadScience instead of Conservapedia because the latter is very likely to get edited or removed. It is also available at PandasThumb, and discussed at ACandidWorld in terms of legal maneuvers vs. Science.

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