He talks about his findings here (public access):
In February 1988, Richard Lenski set up 12 replicate populations of a single genotype of Escherichia coli in a simple nutrient medium. He has been following their evolution ever since. Here, Lenski answers provocative questions from Jeremy Fox about his iconic “Long-Term Evolution Experiment” (LTEE). The LTEE is a remarkable case study of the interplay of determinism and chance in evolution—and in the conduct of science.
A reader writes, “Sounds like Lenski admits that there is no experiment or hypothesis in the traditional sense. I wonder if he would admit that to a popular audience.”
Was the reader thinking of this?
JF: Ok, so let me ask you that. Is the LTEE actually an experiment, and wouldn’t it have been even better if it was? It’s just one “treatment”—12 replicates of a single set of conditions. Wouldn’t it have been even more interesting to have, say, two treatments? Two different culture conditions, two founding genotypes, or two founding species?
RL: You’re certainly right, Jeremy, that experiments in the fields of ecology and evolutionary biology typically have two or more treatments. But that’s not an essential part of the definition of an experiment. It would have been nice, perhaps, if the LTEE did have two or more environments and/or two or more ancestors, as you suggest—in fact, we’ve run several of those types of experiments over the years, and I’ll mention a few of them below.
The reason I didn’t do that with the LTEE, though, was because one of my core motivating questions concerned the repeatability of evolutionary dynamics across replicate population. That’s a question about the trajectory of variances over time, which is challenging statistically because estimates of variances have large uncertainties. So if the LTEE had two treatments, I might have been able to say something about the differences between them, but I would have had less power to say anything about the among-replicate variances for either treatment. So for that motivating question, going from 12 replicate populations down to 6 replicates would have been risky.
Well, um, no, not in the traditional sense. Only design requires evidence. And all such evidence is dismissed in principle.
Evolution today is NOT about evidence. That is because we are at the frontier of an impasse that Darwin’s followers can’t help us bridge.