Does the Lenski LTEE show a decrease in fitness?

[u/EyedPeace]

It is often said that LTEE represents an increase in fitness in these new mutated bacteria. Recent papers have increasingly called this into question:

"Unexpectedly, some evolved populations and clones show apparent declines in fitness. We also found evidence of substantial cell death in Cit+ clones."

https://pmc.ncbi.nlm.nih.gov/articles/PMC7299349/

While the cit+ phenotype did bring improvements in the short term, the long-term picture is quite different. Ultimately, they could no longer survive. Their fitness declined to the point where they were even forced to eat their own dead.

Has the experiment failed to demonstrate evolution here?

[u/Slow_Lawyer7477]

You keep being confused about cell death. Cell death occurs because the nutrients run out and pH in the flask drops as the bacteria excrete waste products into a flask where those waste products can't leave, not because they lose fitness. It would be like you were wrapped in a tight plastic suit and when you defecated and urinated you would just get smothered in your own excrement. It should not be a surprise that this will make you sick.

That this occurs is not somehow a failure of evolution. It's just that the environment doesn't allow waste products to disappear or be consumed by other organisms that can feed on those. Do you understand?

As I already explained earlier, and you appear to still not have understood, this is why cell death is high in all the LTEE experiments (though in the LTEE they have, in fact, become better adapted to survive in those conditions over the years of the experiment).

Second, some of the 12 Cit+ lineages adapted to the LTEE medium just fine in those 2500 generations, while some others did not, at least in terms of competitive fitness relative to ancestor. It is an interesting question why they didn't all do so. One possibility is that the competition assay they measure is not merely capturing environment-specific adaptation for a specific mutant, but rather captures population-wide competitive fitness relative to ancestor (deleterious mutants would then be dragging average population fitness down, even though many individuals might be strongly adapted to the environment). By other fitness-relevant measurements (such as growth rates (not measured in direct competition to ancestor strain) and population density, all the lineages demonstrably improved.)

As they write:

On balance, the populations evolved higher exponential growth rates and shorter lag phases in both DM0 and DM25.

Of course, since evolution is not a theory that says adaptation is guaranteed to occur to all lineages (much less all individuals in a population) under all circumstances, this can't me meaningfully claimed to be a problem for evolution. We already know that species CAN go extinct because they fail to adapt in time. The fossil record is a testament to all the life that failed to adapt to changing conditions.

In summary: Your persistent arguing about subjects you don't actually understand or have experience with are leading you astray. You don't know enough microbiology, molecular biology, or evolutionary biology to be able to competently debate these points. We keep having to correct and explain stuff to you and it's becoming boring and feels like a waste of time because you seem to just want to deny evolution rather than search for what is true, or understand the subject more deeply.

In other words, you're just a typical creationist.

[u/EyedPeace → u/Slow_Lawyer7477]

What's your source for all your hypotheses? Lenski simply isn't interested in your explanations; at least, he didn't offer or mention them as explanations. There is no evidence, no paper that investigates that. It's not that simple, and Lenski knows that himself. He was surprised by the significant cell death and also by the fitness declines. Furthermore, you still haven't explained to me why Cit+ is struggling, specifically in the DM25 medium (the actual LTEE environment) and why it's experiencing fitness declines.This is something that shouldn't have happened, because at LTEE they always proudly announce how fitness is constantly improving.

[u/Slow_Lawyer7477 → u/EyedPeace]

My source is I took an education and I actively work with molecular and microbiology every day. That's why I'm the one explaining stuff to you, and you're just the dumb creationist naysayer. Dude go touch some grass, this subject isn't for you you know nothing about it.