Bacterial Simplification

I wonder – does the ICR have a google alert set up for “Richard Lenski,” or for “Morris”? Anyway, Brian Thomas’ April 30th article, New Theory: Evolution Goes Backward, comments on a paper called The Black Queen Hypothesis: Evolution of Dependencies through Adaptive Gene Loss, by J. Jeffrey Morris, Richard E. Lenski, and Erik R. Zinserc.

If you’re wondering, and can’t be bothered to click the link, here’s where the name comes from:

We present the Black Queen Hypothesis (BQH), a novel theory of reductive evolution that explains how selection leads to such dependencies; its name refers to the queen of spades in the game Hearts, where the usual strategy is to avoid taking this card. Gene loss can provide a selective advantage by conserving an organism’s limiting resources, provided the gene’s function is dispensable.

And so on. Read it all – it’s open access after all.

The question is, how much of that does a bacterium actually *need*?

Brian begins:

Microbiologists contend that instead of increasing complexity, evolution of some systems—like interdependent microbial communities—can occur by losing complexity. How accurate or meaningful is this new idea about “reductive evolution,” whereby life evolves by losing genes?

A better summary would be to say that “complexity” is independent of evolution; that while evolution can increase complexity, it can also reduce it. For an analogy for what is going on here, consider a computer program ditching some segments of its code, relying on the environment and other programs to perform the function that they formerly carried out.

By the way, this article is unusual in that it is one of those ones where he references the paper, but gives no more than that – this article is entirely his own speculation. In other words, it’s him that’s judging “how accurate or meaningful is this new idea [is]” – nobody else.

The authors described their new hypothesis of evolution in the online journal mBio. They formulated this reductive evolution concept after they observed ocean-living bacteria losing genetic information.

The bacteria lost particular vital functions by somehow letting go of the genes that aided those functions. The bacteria survived by relying on nearby microbes to perform that vital task for them. Without devoting resources to that function, the bacteria are free to perform other roles more economically.

And why shouldn’t they? The point is that it is advantageous for the organism to do so, and thus natural selection shines on it. The authors say that the BQH:

…may explain the observed nonuniversality of prototrophy, stress resistance, and other cellular functions in the microbial world.

In other words, they explain the fact that not all bacteria photosynthesis by the ones that don’t do so being able to leech off the ‘leaky’ process taking place in other organisms. But they don’t all ditch the process, as after a threshold is passed it is no longer beneficial to not be carrying out photosynthesis, relative to the advantages gained. Or, as they say:

The BQH predicts that the loss of a costly, leaky function is selectively favored at the individual level and will proceed until the production of public goods is just sufficient to support the equilibrium community; at that point, the benefit of any further loss would be offset by the cost.

Brian continues:

To these evolutionists, when bacteria lose genes, “reductive genome evolution” is occurring. But they admitted, “There is a tendency in evolutionary discourse to describe life’s history as a progression towards increasing complexity.” So has evolutionary discourse been misguided? Instead of simple-to-complex, was life’s history instead filled with complex-to-simple evolutionary changes such as bacteria losing certain genes?

Right after that quote in the paper, the authors continue in the next sentense:

…there is no reason to expect that complexity will be selectively advantageous at all times and for all species.

So Brian is misguided, yes. They are not saying that “life’s history [is] filled with complex-to-simple evolutionary changes such as bacteria losing certain genes,” but merely that evolution does not have to always favour complexity, and in some times and places it will be disadvantageous to hold onto it. That is all – or rather it isn’t, as you discover if you read the rest of that paragraph, but rest assured that it doesn’t help Thomas at all. I don’t want to provide spoilers, so let’s continue with B.T.:

Life’s history is often described as a progression because without a Creator, transforming hydrogen into humans required some kind of natural progression. One cannot climb a hill by falling down a hole.

You’ve heard of molecules-to-man, and particles-to-people – now we have “hydrogen into humans”. It all makes the same in the end.

And one may not climb a hill by falling down a hole, but that’s not a great analogy for what’s going on here. Instead, merely note that you don’t climb to the summit of Everest from the shoreline on a route that never, ever takes you down even a little way. That would be rather difficult and pointless.

Brian concludes:

But these study authors inadvertently showed why the story of simple-to-complex evolution is not scientific. They did not observe nature constructing bacterial genes, but they did observe bacteria losing genes. Gene loss may be termed “evolution” by some, but it provides absolutely no support for big-picture evolution. If evolution describes both the reduction and addition of genes, then it really doesn’t describe anything.

The trouble with his closing statement there is that it’s the equivalent of saying “If the laws of motion describe my car as it travels both backwards and forwards, then they really don’t describe anything.”

And I shouldn’t have to explain how that’s nonsense.

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9 thoughts on “Bacterial Simplification

  1. Good work. I don’t know how you stay sane reading all this stuff. It’s not just stupidity. A lot of the time they’re wilfully misinterpreting the claims of science.

    • Thanks.
      With some difficulty, I must admit. But it’s always nice to find the overlooked aspect, whatever it is, that scuppers the argument made – that makes up for it all in my opinion.

  2. To echo again my comment made under a preceding ‘Eye’ post:

    I sent the following email to the ICR:

    http://www.icr.org/article/6770/
    The new hypothesis relates to BACTERIA.
    And there is no obvious and scientific basis for the ICR suggesting,
    on the back of it: “Instead of simple-to-complex, was life’s history
    instead filled with complex-to-simple evolutionary changes such as
    bacteria losing certain genes?”.
    “If evolution describes both the reduction and addition of genes, then
    it really doesn’t describe anything.” Your SENTENCE doesn’t describe
    anything. Natural selection acting on mutations CAN alter gene pools.

  3. I reckon a lot of discourse on evolution – particularly in the public sphere – has been misguided. All too often it is viewed as a “ladder” with organisms climbing up it towards some ideal goal.

    This paper provides yet another reason why this is silly.

    • Sadly I haven’t. My best reply to this situation is just to note how cheetahs are faster, sharks better swimmers, humans more intelligence. There’s no distinct path they’re trying to follow, they’re just adapting in different ways.

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