lenski experiment

[jfoldbar]

i stumbled across the whole lenski this and think its great that someone had the foresight to do something like this.

however i do wonder, after 50000 generations, has anythingt happened of any significance?

i mean, if evolution is a fact/true, why are the ecoli still ecoli? why havnt they evolved to something else of any real difference? 

dont get me wrong, i think evolution makes a lot more sense than creation, but it doesnt help the evolution case if those ecoli always stay as ecoli, and never evolve to anything else.

 

[beecee]

45 minutes ago, jfoldbar said:

i stumbled across the whole lenski this and think its great that someone had the foresight to do something like this.

however i do wonder, after 50000 generations, has anythingt happened of any significance?

i mean, if evolution is a fact/true, why are the ecoli still ecoli? why havnt they evolved to something else of any real difference? 

dont get me wrong, i think evolution makes a lot more sense than creation, but it doesnt help the evolution case if those ecoli always stay as ecoli, and never evolve to anything else.

 

I'm not knowledgable  enough to explain why ecoli are still ecoli, except to say that evolution takes place over a macro scale, and is as certain as any scientific theory can be as to its validity. What I do know is that we do have  evidence of certain bacteria becoming resistant to  penicillin and other drugs. Also we have so called "superbugs" that seemed to have evolved in hospitals and other clean environments such as Golden Staph.

Someone should be along in time to explain more fully.

Edited September 8, 2017 by beecee

[Arete]

Some of the populations evolved to "eat" a completely new "food".

I guess to flip this around - the E. coli populations are being evolved under a neutral model. The time to divergence of two allopatric populations in generations is 4 x effective population size x mutation rate.  Given this, you would not expect "speciation" in the Lenski experiment in the given time frame. 

Edited September 8, 2017 by Arete

[jfoldbar]

wiki says the experiment has clocked more than 60000 generations.

does this equate to more than 1 million humans years. if 1 generation for humans is 20 years (from birth until they can themselves reproduce) then that is 1.2 million years.

evolution theory says a quite bit of speciation has happened in that time. so why not much with the ecoli?

[Arete]

On 9/18/2017 at 2:18 AM, jfoldbar said:

evolution theory says a quite bit of speciation has happened in that time. so why not much with the ecoli?

It does? Again the populations are raised in as neutral conditions as as possible. Why do you expect "speciation" in 60,00 generations under neutrality? Mathematically, it would not be plausible in the absence of divergent selection. 

[jfoldbar]

we have seen speciation in a few hundred generations of bird etc, so why not more speciation in 60,000 generations

[CharonY]

8 hours ago, jfoldbar said:

we have seen speciation in a few hundred generations of bird etc, so why not more speciation in 60,000 generations

The key word you keep missing is "neutral conditions". If we do not have selection or other shaping factors, populations separate  purely by stochastic means. That is where the link provided by Arete comes in (take a look at it). Divergence then takes much longer. Also take a look at Hardy Weinberg to see when divergence never happens.

Edited September 20, 2017 by CharonY

[jfoldbar]

sorry. im a laymen. i dont understand what you mean. but i think you mean that the lab experiment is set up to try to minimise evolution by keeping interference to a minimum. which is opposite to nature. 

but if this is the case,  wouldnt an experiment thats trying to study evolution work better if evolution can happen?

[Arete]

24 minutes ago, jfoldbar said:

sorry. im a laymen. i dont understand what you mean. but i think you mean that the lab experiment is set up to try to minimise evolution by keeping interference to a minimum. which is opposite to nature. 

but if this is the case,  wouldnt an experiment thats trying to study evolution work better if evolution can happen?

Evolution  does not necessarily equal speciation. The question you are asking is answered by the fundamentals of neutral theory. Divergence, in the absence of divergent selection proceeds scholastically at a rate of 4Ne x u, where Ne is effective population size and u is the mutation rate. See previous link. 

The goal of the long term experiment was to examine neutral rates of evolution, not adaptation in the face of selective pressures, although spin off experiments have done that. 

Another major caveat is that no one really has a good definition of what a bacterial "species" is - for e.g. Shigella and E. coli are effectively the same thing.

Edited September 20, 2017 by Arete

[Daecon]

Obviously those bacteria are at the apex of their evolutionary niche for existing in petri dishes, and therefore don't need to evolve any further.

Like crocodiles or cockroaches.