Richard Lenski’s lab is supposed to demonstrate Darwinian evolution over endless generations of bacteria:
The new paper now reports on 2,500 generations of further evolution of the citrate mutant, in nutrient media that contains either citrate alone or citrate plus glucose (as for earlier generations). As always with the Lenski lab, the research is well and thoroughly done. But the resulting E. coli is one sick puppy. Inside the paper they report that “The spectrum of mutations identified in evolved clones was dominated by structural variation, including insertions, deletions, and mobile element transpositions.” All of those are exceedingly likely to break or degrade genes. Dozens more genes were lost. The citrate mutant tossed genetic information with mindless abandon for short term advantage.
In a particularly telling result, the authors “serendipitously discovered evidence of substantial cell death in cultures of a Cit+ clone sampled from … the LTEE at 50,000 generations.” In other words, those initial random “beneficial” citrate mutations that had been seized on by natural selection tens of thousands of generations earlier had led to a death spiral. The death rate of the ancestor of the LTEE was ~10 percent; after 33,000 generations it was ~30 percent; after 50,000, ~40 percent. For the newer set of experiments, the death rate varied for different strains of cells in different media, but exceeded 50 percent for some cell lines in a citrate-only environment. Indeed, the authors identified a number of mutations — again, almost certainly degradative ones — in genes for fatty acid metabolism that, they write with admirable detachment, “suggest adaptation to scavenging on dead and dying cells.”
The degraded E. coli was eating its dead.
Lessons to Draw
Let me emphasize: the only result from the decades-long, 50,000-plus generation E. coli evolution experiment that even seemed at first blush like it had a bit of potential to yield a novel pathway in the bacterium has resulted instead in spectacular devolution.
Michael Behe, “Citrate Death Spiral” at Evolution News and Science Today
Paper. (open access)
Yes, of course that’s true. But it no longer matters. As science devolves into myth, the popular narrative prevails over the correct one. The popular narrative is easier to teach because it fits in better with prevailing opinion.
See also: Darwin Devolves Much “evolution” is about breaking or blunting complex equipment in order to arrive at a simple solution for survival.
Has anyone here heard the proverb “Silks and satins put out the kitchen fire”? Think about what it means.