Posted on by bort901

Richard Lenski is an evolutionary biologist who studies evolution by analyzing changes in bacterial populations. Perhaps he is most famous for his long-term experiment where his group identified a population that evolved to use a nutrient (citrate) that E. coli normally can’t use. This was a very important finding as it provided proof-of-concept that random mutations alone are sufficient to induce new functions.

In a recently published paper in Nature, Lenski takes the above experiment and analyzes the frequency of mutation throughout these populations. The goal of this paper was not to show which specific mutations led to the ability of the bacteria to use the new nutrient source. The goal was to look at the level of overall mutation rate during the experiment. In the authors own words:

The relationship between rates of genomic evolution and organismal adaptation remains uncertain, despite considerable interest. … Thus, the coupling between genomic and adaptive evolution is complex and can be counterintuitive even in a constant environment. In particular, beneficial substitutions were surprisingly uniform over time, whereas neutral substitutions were highly variable.

Of course the Discovery Institute and ID proponents are not going to keep quiet about any work coming from Lenski’s lab as their work provided such an important part of the evolutionary puzzle. Michael Behe took up the challenge this time and wrote an entry at Evolution News and Views. Lets address some of Behe’s points.

Behe’s first compliant is that

[Lenski’s group] identified a couple score of mutations which they say are likely beneficial ones. That is almost certainly true, but what they don’t emphasize is that many of the beneficial mutations are degradative — that is, they eliminate a gene or its protein’s function.

First, Behe is attacking the paper for something that is really irrelevant to the point of the paper. It also doesn’t disprove the original result of that spontaneous mutations that led to a novel attribute. It is a red herring designed to poke holes in Lenski’s work instead of directly arguing against it. So why all the degradative mutations? Well, these experiments were done in a lab under strict conditions (single temperature, no other organisms, defined nutrients) to eliminate other variables. Without these other stimuli, is it any wonder that most changes are degradative?

Behe also criticizes the rise in what is called a mutator line in these experiments. A mutator strain is one in which mutations arise more frequently than in a normal strain. Again this doesn’t really address the ideas of the new paper or in the proof-of-concept of Lenski’s original data.

Anyway, who cares that these strains became mutator strains. A mutator just increases the frequency by which mutations arise. Maybe it would have taken 3 times as long for the beneficial mutation to arise if the mutator strain hadn’t evolved. It doesn’t change the fact that the cells evolved into a state where they could use a nutrient that they couldn’t before. Besides, it is a moot point as one of the original mutation had arose before the 20,000 generation, a time before the mutation that led to mutator strain had occurred.

Finally, Behe closes with the expected tactics that we have grown to love from ID proponents. The first tactic as illustrated above is to wrongfully criticize valid experiments in favor of evolution. The second tactic is then to say how this data really proves intelligent design:

Lenski’s decades-long work lines up wonderfully with what an ID person would expect — in a huge number of tries, one sees minor changes, mostly degradative, and no new complex systems. So much for the power of random mutation and natural selection.

First, an ID proponent would not expect the E. coli to ever use the new nutrient. The “power of random mutation and natural selection” led the bacteria to a whole new attribute. Don’t forget, this experiment lasted only decades, or 1/100,000,000 the time bacteria are believed to inhabit the earth. Finally, like I stated above, these were very unnatural conditions that would never be experienced during normal life on earth.

Filed under: absurdity | Tagged: bacteria, E. coli, Michael Behe, Richard Lenski | 4 Comments »