Evolution starting with a single bacterium

Bacteria have almost no (or none??) "junk DNA." Their genomes are vastly simpler than those of us profligate eukaryotes.This message has been edited by Coragyps, 06-10-2004 10:09 PM

I am still amazed about the experiment presented by Rrhain on the first page. Just a question for comprehension: The experiment seems to be repeatabel ... and the ratio of surviving bacteria matches within a confidence interval, perhaps of 95%, right?
Let try to make a simplified model. I have to guess the numbers but hopefully there is someone who is better informed and may help me with assuming the following:
1 stem E. coli bacterium of K-type
- let them reproduce to get a population of 10 000 000 000
This means rounded 34 generations.
- Assuming the new bacteria (K-4 because they are immune to T4 phage) have to exist in numbers to survive, say 0.1 % = 10 000 000To yield an comparable number the mutation must have occurred several times or
one time at an early stage, example given at generation 14.Is it that likely that the mutation happens, and get inherited even if there is no positive selection until the T4 phage comes in? There should be an idea how many roads a mutation can go in order to calculate the likelihood. The grand total of mutations may be subtracted by those which lead to tethal outcome. if the more or less neutral mutation may bear a positive effect on future events like the advent of the T4 phage it may be a huge number to get the proper one.There were a lot assumptions because of missing background, but I hope there will be postings to adjust those. Anyway, I hope I made clear why I doubt the explanation.crashfrog wrote

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They have that built-in, random mechanism of adaptation. It's called "mutation and natural selection." It's the mechanism the experiment proves exists, and it's the same mechanism that does the same thing in all other organisms.

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Why propose an additional, unknown, untestable mechanism when we already have one that explains it just as well? How would you determine the difference between your unknown mechanism and the evolutionary mechanism, since the results are exactly the same in every case?

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Actually, I am not a scientist in this field, so I don't know if this proposed mechanism will be untestable. It simply appears to me that the given explanation of the phenomenon is not convincing. Just as if there is thunder ther must have been a god calling.

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So I see, but the problem is, you don't doubt my evidence or reasoning, you doubt the conclusion.

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What makes you think this way? I am just focused on the phenomenon presented and curious about a good explanation. Perhaps you can show me were I got it wrong.This message has been edited by scot-free, 06-11-2004 03:55 PM

If it happens, it'll always be inherited. Bacteria reproduce asexually, not sexually, so there's no sexual selection of traits. Why bother calculating the likelyhood? We know it happened. What on Earth would the likelyhood tell us that the actual experiment hasn't already? Well, it will be until you can think of a situation where evolution and the unknown mechanism you propose would give different results. As it stands now we've got evolution, and then we have your unknown mechanism, which operates exactly like evolution in every case involving bacteria, apparently. How are we supposed to tell the difference?Do you see the problem yet? On one hand, we can explain it with a mechanism we have observed in other situations. But you would have us believe that a mechanism that only exists in bacteria and only reacts in this situation - and when it does act, acts exactly the way evolution is expected to - is responsible.That's what I mean by "untestable." It means that you've defined the mechanism in such a way that it can never be distinguished from evolution by any test. The fact that you and I agree on all the evidence, and we agree that all the alternative explanations are wrong. It's just that when it comes to taking the next logical step - the only remaining explanation is the most likely - you refuse to go. Why would that be except that you don't like that conclusion? We have a good explanation. It's called "evolution by random mutation and natural selection." It involves mechanisms we can test and observe, and it's falsifiable. It's a good explanation by any scientific measure.

Hi crashfrogI didn't dive into the facts yet, as I have to look it up and gather additional information. Further, I only said that I doubt your explanation yet. This doesn't mean that I came already to a conclusion. Your explanation may be right, but it should prove it doing some ground work. What I advocate is to be skeptic on every claim, religious as well as so-called scientific. True sciences appreciate skepticism, even when it falsifies a theory.When a question cannot be resolved eventually we may decide on leave as is, for instance on issues which are not important. Or we make our own judgement. But this would only be valid if we considered the facts.

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Why bother calculating the likelyhood? We know it happened. What on Earth would the likelyhood tell us that the actual experiment hasn't already?

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Because that is science. We are looking for explanations to be convincing. If we take the easy road and being satisfied with a quick answer we are no better than simple minded persons to associate thunder with the voice of god.
To get a solid model including the likelihood of mutations we get more insight to avoid the fallacy of ignorance. If it could be elaborated that there are other naturalistic mechanisms working than mutation and selection it has limited impact on evolution.Additional mechanisms if turned out to be true may also be result of evolution. Or, if it works the way you consider, it may still be that creation is significant. The only thing to say is: Do we have a specific element here to support evolution or not? But as long as the model isn't clear to me I don't mind on the impact.

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Well, it will be until you can think of a situation where evolution and the unknown mechanism you propose would give different results. As it stands now we've got evolution, and then we have your unknown mechanism, which operates exactly like evolution in every case involving bacteria, apparently. How are we supposed to tell the difference?

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I tried to figure that the explanation of mutation and selection are not convincing in this case. I don't discuss evolution in general here. If the mutation story turns out to be convincing I wouldn't see a reason to assume another mechanism. But it is too early for me to accept this. You may have more insight and can help me to get it clear.

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Do you see the problem yet? On one hand, we can explain it with a mechanism we have observed in other situations. But you would have us believe that a mechanism that only exists in bacteria and only reacts in this situation - and when it does act, acts exactly the way evolution is expected to - is responsible.

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That's what I mean by "untestable." It means that you've defined the mechanism in such a way that it can never be distinguished from evolution by any test.

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I don't want you believe anything but that I have scientific doubt at this point. Propbaly others got similar ideas and have checked the concept ... I am searching for the outcome. It seems much too early to say that there will be no way to tell the one from the other.

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The fact that you and I agree on all the evidence, and we agree that all the alternative explanations are wrong. It's just that when it comes to taking the next logical step - the only remaining explanation is the most likely - you refuse to go. Why would that be except that you don't like that conclusion?

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I think you may be too fast for me or much better informed. Alternative explanations should always be considered as long as the case isn't closed. I am not refusing to accept a good explanation, the random mutation story may be factual, but this is not confirmed yet ... I need more information.

As far as I'm concerned, it proves it by being the only scientific explanation that isn't contradicted by the experiment and is consistent with observations of other forms of life. And I do. But scepticism doesn't mean you can't ever agree that something is the most likely explanation. By all means, keep asking questions. It's just that I wish you would ask ones that the experiment itself didn't answer for you, you know? Why, though? We know mutations happen. We know selection occurs. We know both of those occured in the experiment, because they always occur. We know that they have the capability to explain what happened in the experiment, so what's the hold-up? Why look farther when we've already got an explanation that works? What about this one isn't enough for you? If you can construct a falsifiable, scientific, alternate explanation, I'll consider it. But believe me when I tell you that evolution is accepted as the mechanism here because it's the most parsimonious and consistent explanation we know of.

Any fossil evidence of?

What exactly do you think would fossilize?

I'll take that as a no.
I guess another question would be- is there any evidence at all of anything preceeding a prokaryote?

Instead, why don't you take it as a question, as it was intended, and just answer it? Here, let's try again: Exactly what do you think would fossilize?

I would ask that you try again, I am happy with my first try. Here we are talking about chronological order in biogenesis, and you aren’t even following proper order in this discussion. This isn’t beginning well is it?You first.
I have asked two questions. You haven't even answered my first on yet.This message has been edited by XenoGenisis, 06-23-2004 03:26 AM

Don't play games.You tell me what parts of the organisms you're talking about could fossilize, and I'll tell you if we have any fossils like that. It's pretty simple.

What organisms?

The ones you're asking about. Duh!

I didn't know that there were any predecessors to prokaryotes. Are you saying that there are? Were have come full circle.

I think that the Archea are taken as being examples of something like the precurssors.