Yet more evidence of evolution

rhadamanthus · Jun 10, 2008

http://www.newscientist.com/channel...make-major-evolutionary-shift-in-the-lab.html

This is neat, but no doubt someone will get all ticked about it - ergo I put it in the D&D.

A major evolutionary innovation has unfurled right in front of researchers' eyes. It's the first time evolution has been caught in the act of making such a rare and complex new trait.

And because the species in question is a bacterium, scientists have been able to replay history to show how this evolutionary novelty grew from the accumulation of unpredictable, chance events.

Twenty years ago, evolutionary biologist Richard Lenski of Michigan State University in East Lansing, US, took a single Escherichia coli bacterium and used its descendants to found 12 laboratory populations.

The 12 have been growing ever since, gradually accumulating mutations and evolving for more than 44,000 generations, while Lenski watches what happens.

Profound change
Mostly, the patterns Lenski saw were similar in each separate population. All 12 evolved larger cells, for example, as well as faster growth rates on the glucose they were fed, and lower peak population densities.

But sometime around the 31,500th generation, something dramatic happened in just one of the populations – the bacteria suddenly acquired the ability to metabolise citrate, a second nutrient in their culture medium that E. coli normally cannot use.

Indeed, the inability to use citrate is one of the traits by which bacteriologists distinguish E. coli from other species. The citrate-using mutants increased in population size and diversity.

"It's the most profound change we have seen during the experiment. This was clearly something quite different for them, and it's outside what was normally considered the bounds of E. coli as a species, which makes it especially interesting," says Lenski.

Rare mutation?
By this time, Lenski calculated, enough bacterial cells had lived and died that all simple mutations must already have occurred several times over.

That meant the "citrate-plus" trait must have been something special – either it was a single mutation of an unusually improbable sort, a rare chromosome inversion, say, or else gaining the ability to use citrate required the accumulation of several mutations in sequence.

To find out which, Lenski turned to his freezer, where he had saved samples of each population every 500 generations. These allowed him to replay history from any starting point he chose, by reviving the bacteria and letting evolution "replay" again.

Would the same population evolve Cit+ again, he wondered, or would any of the 12 be equally likely to hit the jackpot?

Evidence of evolution
The replays showed that even when he looked at trillions of cells, only the original population re-evolved Cit+ – and only when he started the replay from generation 20,000 or greater. Something, he concluded, must have happened around generation 20,000 that laid the groundwork for Cit+ to later evolve.

Lenski and his colleagues are now working to identify just what that earlier change was, and how it made the Cit+ mutation possible more than 10,000 generations later.

In the meantime, the experiment stands as proof that evolution does not always lead to the best possible outcome. Instead, a chance event can sometimes open evolutionary doors for one population that remain forever closed to other populations with different histories.

Lenski's experiment is also yet another poke in the eye for anti-evolutionists, notes Jerry Coyne, an evolutionary biologist at the University of Chicago. "The thing I like most is it says you can get these complex traits evolving by a combination of unlikely events," he says. "That's just what creationists say can't happen."
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MadMax · Jun 10, 2008

I'm pissed about this, rhad.

rhadamanthus · Jun 10, 2008

MadMax said:

I'm pissed about this, rhad.
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I knew it!

DaDakota · Jun 10, 2008

Neat, that is a cool experiment.....

DD

weslinder · Jun 10, 2008

31,500th generation
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630,000 E. Coli years, one new trait developed. Interesting, but not exactly a smoking gun for evolutionary biologists.

rhadamanthus · Jun 10, 2008

weslinder said:

630,000 E. Coli years, one new trait developed. Interesting, but not exactly a smoking gun for evolutionary biologists.
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To be fair - nature would provide more than 12 populations too.

weslinder · Jun 10, 2008

rhadamanthus said:

To be fair - nature would provide more than 12 populations too.
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Yeah, I'm just being contrarian.

rhadamanthus · Jun 10, 2008

weslinder said:

Yeah, I'm just being contrarian.
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Meanie.

twhy77 · Jun 10, 2008

Science is like so unrational.

Mulder · Jun 10, 2008

I know!!! Let's develop MUTATED E. COLI Bacteria!!!

What could possibly go wrong?!?!

Apollo Creed · Jun 10, 2008

Mulder said:

I know!!! Let's develop MUTATED E. COLI Bacteria!!!

What could possibly go wrong?!?!
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pmac · Jun 10, 2008

Well, there's no absence of evidence....

does that mean there is or isn't evidence of absence?

what?

rhester · Jun 10, 2008

Wow!

Thanks

Invisible Fan · Jun 10, 2008

It reminds me of the AI sim evolution experiment....

Classic · Jun 10, 2008

rhadamanthus said:

To be fair - nature would provide more than 12 populations too.
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How did the observed bacteria get there? Oh right, somebody put it there.

gwatson86 · Jun 11, 2008

Classic said:

How did the observed bacteria get there? Oh right, somebody put it there.
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Which, I suppose, leads to the question: Why can't creationism and evolution coexist? It doesn't seem too far-fetched to believe that an original creation could evolve.

But maybe I'm just wishy-washy.

pirc1 · Jun 11, 2008

gwatson86 said:

Which, I suppose, leads to the question: Why can't creationism and evolution coexist? It doesn't seem too far-fetched to believe that an original creation could evolve.

But maybe I'm just wishy-washy.
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If you are talking about creation of universe, at the present no one knows how it happened, it could be some "God" that created the whole thing. However, if you are talking about the creation of man, it almost certainly was not done by God like it was stated in the bible.

Rashmon · Jun 11, 2008

As long as they notify me in advance before they teach this to my child in school.

HAYJON02 · Jun 11, 2008

Classic said:

How did the observed bacteria get there? Oh right, somebody put it there.
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How did you observe it being put there? That's amazing! And so simple!

MadMax · Jun 11, 2008

pirc1 said:

However, if you are talking about the creation of man, it almost certainly was not done by God like it was stated in the bible.
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tell me how you think it's stated in the Bible.

i'm not a creationist in a literal sense. i believe there was a creator who created creation. i don't worry much about whether the creation story happened with detail, because detail isn't really provided. god breathed life into creation. the bible poetically says he spoke it into existence, written by people thousands of years ago without the benefit of a microscope.

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