• Evolution by Gene Duplication

    For a long time, creationists have insisted that evolution can’t add information to a genome.  In general, they never defined (and stuck with said definition) information.  The thinking behind this was because most mutations are harmful (which, we now know to be incorrect, but creationists aren’t really up on the latest research (even if the research is from 2000[1])).

    But, creationists have long been asked “what about duplication?”.  To which the creationists have replied, “there’s no evidence”.  Well, there is now.

    This paper (published in Science, Oct 31, 2012) describes how gene duplication can easily result in not two, but dozens of variants in a mere 3,000 generations.  Let’s look at what they did.

    First the researchers got a bacteria (Salmonella enterica in this case) and gave it a particular gene.  Now this gene gave the bacteria a weak ability to survive without the amino acids histidine and tryptophan.  The gene basically produced an enzyme that could (again, weakly) catalyze the production of both amino acids.

    This was determined to be the case by placing the bacteria in a medium that lacked both histidine and tryptophan and then seeing if they were able to survive, grow, and reproduce.  Which the bacteria did.  Averaging about 5 hours between cell divisions.  However, if they placed some histidine in the growth medium, then the cell division time dropped to 2.6 hours.  If there was tryptophan and no histidine, the cells divided every 2.9 hours.  If both amino acids were present, the cell doubling time dropped to 1.5 hours.

    So, the strains that were in the no histidine/no tryptophan growth medium were stressed.  They could survive and grow, but they weren’t good at it (as shown by the increased reproduction time).

    I’ve tried to think of way to say this that was both cool and not anthropomorphic, but I couldn’t think of one.  So, let’s just say that evolution happened.  Evolution is always happening.  Genes mutate, populations grow, compete, die out, etc. based on those genes.  Well, in the case of this lab experiment, the end result was that evolution not only produced genes that were good at producing histidine and tryptophan, it also resulted in bacterial species with multiple genes.

    The gene was duplicated.  That’s simply it, their was a mutation whose result was two copies of the same gene.  Now, things really get interesting.  Most of the time, if you have two genes producing a catalyst, then you get more catalyst.  That happened, but you also have the ability to radically mutate one of the copies of the gene without harming the organism.

    And that’s the real benefit to gene duplication events.  Because a mutation that would kill the bacteria could happen in one gene, but the other gene is still there, still functional and the organism lives.  But again, selection takes over and there are many cases of what I call “potentiating mutations”.  These mutations may be neutral or even harmful, but they are required for a future mutation that results in massive increases in functionality.

    So, after 3000 generations of bacteria (that’s about two years) what were the results?  Oh this is really good.  You’re gonna love this.

    There wasn’t one population with two genes.

    There were over 32 unique populations with different types of genes.  Some of them had two genes, one that did histidine production and one that did tryptophan production.  Some of them had a single gene that did both really well.  And there wasn’t just one version of each of the three.  There were over 11 unique alleles for these genes present in the various lineages and populations.

    In two years (roughly, that’s an estimate from the 3000 generations and the average generation time), there was  a massive divergence in the bacterial populations.  Some of the versions of the gene had a 20-fold improvement in catalytic activity.

    Thus, the creationists are wrong.  We all knew it, but now there’s another tool in the arsenal against their arguments.

    I’d like to add something.  Many creationists will come up with this pathetically stupid argument.

    All this experiment shows is that intelligently designed experiments result in changes consistent with Intelligent Design.

    Well, no.  It doesn’t show that at all.  Yes, experiments are intelligently designed.  They must be.  The entire goal of an experiment is to reduce the variables down to one variable that is controlled by the experimenters and one variable that is controlled by that variable.  This allows the determination if the controlled variable (also called “independent” or “manipulated” variable) is directly responsible for changes in the other variable (called the “dependent” or “responding” variable).

    What the Intelligent Design proponents are saying with this argument is that the experimenter is a variable within the experiment.  This is not the case.  Just like an intelligently designed roulette wheel still produces random numbers, experiments produce results that often confound the researchers. The whole point is to remove humans from the equation and only observe what happens to X when Y changes.  Ideally, the researcher does nothing more than design the experiment and start it.  No more human input or influence until the end of the experiment.  Humans create all kinds of terrible errors in things.

    If we knew the results of the experiment (i.e. the “front-loading” argument), then there would be no point in doing the experiment.  And casino game engineers would all be mufti-billionaires.

    [1]  Nachman, M. W. and S. L. Crowell. 2000. Estimate of the mutation rate per nucleotide in humans. Genetics 156(1): 297-304.

    Category: CreationismEvolutionScience


    Article by: Smilodon's Retreat