Freethought & Rationalism Archive

Charles Darwin · 09-21-2003, 08:48 PM

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To change a fish into a giraffe you are going to need a whole lot of biological variation in a whole bunch of small steps. And in each one of those small steps, non of the biological variation was created due to selective pressure. You have conveniently missed my point and gone off on a tangent about how selective pressure makes evolution a non random process. So what? No one said otherwise.
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Originally posted by Dr Rick
There's nothing "astronomical" in the description you give above.
And if I missed your point, what was it, then? Was it that mutations are astronomical or that selective pressure is astronomical, or are you going to imply that you were once more posting about something other than evolution?

What is astronomical is the number of possible DNA modifications possible. My point was that your random biological variations must find their way through an enormous space of alternatives.

Doubting Didymus · 09-21-2003, 09:01 PM

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Originally posted by Charles Darwin
What is astronomical is the number of possible DNA modifications possible. My point was that your random biological variations must find their way through an enormous space of alternatives.

So you're saying that you think its too unlikely that any random mutations would ever be beneficial with such a large range of possibilities. Is that right? If so, Isn't the point refuted with some examples of beneficial mutations that have, in fact, got lucky? After all, the 'bad' luck doesn't compund with each generation: any good hits are kept, and you roll the dice again, yes?

Charles Darwin · 09-21-2003, 09:14 PM

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Originally posted by Muad'Dib
Who and when was this? I'd like to take a closer look.

Thanks,
Muad'Dib

Moorehead, Kaplan [Ed.s], *Mathematical Challenges to the Neo-Darwinan Interpretation of Evolution,* 1967. Keep in mind that my point was not the challenge itself, but the circular response.

Charles Darwin · 09-21-2003, 09:27 PM

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I'm asking, what is the probability that this evolution could occur assuming reasonable numbers?
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Originally posted by Dr Rick
The evidence shows that evolution did and still is occuring; there is no good evidence to suggest that it didn't or isn't happening while there exists overwhelming evidence that it did and still is.

You are questioning the probability of an event occuring that has and is occuring. The probability or an event having occured that has occured is one. The answer to your question is "one."

Translation: When all else fails, fall back on the "fact" of evolution. You've got to be kidding me?, no good evidence? Do I have to repeat 20 posts? But then again, what does evidence have to do with it? After all, I'm merely questioning an event that "is occurring." The probability is one! See, this is where evolution has taken us. This is not science.

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Originally posted by Dr Rick
The argument from ignorance is not really an argument; that's why we call it a fallacy.

What makes you "sure" we can assume anything? What reason do we have to assume that your assumptions are accurate?

You have it backwards; your whole argument is an appeal to ignorance.

You are essentially arguing, since we can't account for every detail of evolution, it must be wrong; therefore, creationism.

Sorry, I don't follow. What fallacy is this? Let's see, evolution claims that the most complex things we know of arose all by themselves. They have no actual details showing how this happened. The DNA code and echolocation are supposed to have arisen by themselves. How? Well, we don't know, but it is a fact. And now *I* am the one guilty of a fallacy by questioning this claim?

Charles Darwin · 09-21-2003, 09:41 PM

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Originally posted by Soralis
Let's take a look at some of those questions:

That would basically be the total number of organisms that lived, that were basically within the same species as those organisms that were among those directly along the fish-giraffe line. In one generation, this would be simply all the members of that species. Over a time span such as is involved here, it would be the sum of all the organisms of the species from which giraffes are direct descendants of.

That could be somewhat determined by looking at the genomes of the giraffe and fish, and noting the number of differences between the two. Of course, it's a bit more complicated then that.

First of all, there's the problem of for this to be straightforward, you'd need a 500 million year old fish (if you're going from the first fish to currently living giraffes, rather then from last common ancestor to those that fit into the species giraffe or family giraffidae or such), that would be an ancestor of current giraffes. If you took a currently living fish, it could have a common ancestor with a giraffe, but it also would have changed during all of that time period as well. You can still tell something from the difference there, since if the mutation rate is fairly close, or is known fairly well, then this can still be found out, since they would only start having a difference in mutations from the point of their most recent common ancestors.

There's also the other factor that not all mutations are of the same type, a duplication or inversion could produce a different sequence in far less mutations then point mutations could. Assuming you could recognize duplicated/inverted sequences that had some differences in them from other changes, you could recognize a number of those.

Now that would be much more difficult to account for, since that involves selection, and the environment of the organism. The actual changes wouldn't be made by selection, but if the changes are neutral, negative or positive would be. For example, in a lab situation, if I took a population of bacteria, and at every generation, I sequenced all of the bacteria, and killed any organism with a change, 100% of all changes would be negative. In the same situation, if I instead killed all organisms that were the same as their immediate ancestor, nearly all changes would be positive (the only ones that wouldn't be would basically be those that killed the organism or made it sterile).

To determine the rate of negative/neutral/positive changes would require the knowledge of the environment and situation of every generation, since that ratio would be different depending on the situation. And if you wanted to determine which mutations between fish and giraffe were -/0/+, would not only determine a knowledge of the environment and situation of each generation, but what specific changes were made when, and what changes and effects they had, given that environment, and given the rest of the genetic sequence that currently existed. There would be a greater proportion of them that would be positive, since it would be a descendant that would still be alive.

Hmm.. what do you mean by "fixed" in this context? From what you've previously said, it seems to mean that a specific allele has become very widespread within a population. (perhaps you mean to the exclusion of all other alleles, although that would probably be fairly rare in realistic situations.) Also, as the organisms involved are capable of sexual reproduction, the mutations would not have to happen in sequence from ancestor to descendant. In other words, you wouldn't have to have first one mutation in one generation, and then a second mutation with an organism that already had the first mutation. You could have both mutations arise separately in different organisms, that don't have the other mutation. Then, when those changes spread enough to the point where organisms with one mutation reproduce with organisms that have the other mutation, you can end up having an offspring that has both mutations. This means that the time for a mutation to become more common or fixed within a population isn't an issue for changes made affecting different areas. Different mutations can all happen separately from each other, and then come together in descendant populations. At least for those changes that might not work well without some other change in place. Those that would work better or need a certain other change to work well could still work in this fashion, as long as they could survive long enough on their own, although it's less likely, because of that reason. Which is why sideways transfer (in things such as sexual reproduction, plasmids, etc.) of genetic material is so useful. Since in organisms that reproduce asexually, and don't have such sideways transfer, one mutation would have to happen first, and then the other would have to happen in an organism that has the first, in order for a descendant to have both of them.

How fast a mutation spreads through a population, is dependent on how beneficial that mutation is. There are some equations for this that you can search for, on how fast a specific change will spread through a population, based on how likely an organism is to reproduce with that mutation over not having it, and give an estimate at how long it will take for it to be in a certain % of the population.

Well that depends what question you're asking, if you're asking what's the probability that the evidence that has been collected leads to the conclusion that this processes happened, I'd say so, that's basically been the whole point of this thread, except for a more general case.

If on the other hand, you're asking that if you had a 500 million year old fish, what the probability of a giraffe being it's great^(200 million) grandchild or so, the probability would be extremely small, since it would rely on a large number of chance events and mutations that you couldn't predict in advance. Of course, there's no reason that a giraffe had to exist in the first place, so couldn't be used as an argument against it. It's like flipping a coin 100 times or so, before you flip the coin, the result of getting any particular sequence is the improbable 1/(2^100). However, that can't be used as an argument in reverse, about how that sequence couldn't happen after the fact, since that could be said about any sequence.

If you're asking more along the lines of if the rates of mutation and number of generations and organisms involved would produce the necessary variation in order for such a change to happen, that would be a bit more complex. As well as requiring some estimates of population size within generations and some other factors. You could get some estimates, based on the genetic difference between then two organisms, and how many changes would be necessary for that to happen, and to make it possible for those specific changes to happen.

Excellent thoughts. And no, my point is not in the same category of your coin flipping analogy. Your final paragraph summarizes it better, though we'd need to add questions such as how many mutations are ever going to be helpful in getting to the giraffe; so that mutation rate alone is not sufficient. We'd need to consider how many mutations are harmful, or otherwise will never help get to the giraffe.

Charles Darwin · 09-21-2003, 09:46 PM

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Originally posted by Duvenoy
So, what does all this signify? It depends upon what you�re asking of it. Was echolocation created or evolved?

Echolocation is an excellent means of navigating and finding food. Even the aye-aye�s rather crude method of bug-snagging serves it very well. And yet, extremely efficient echolocators such as pilot whales kill themselves yearly, stranded on a beach. I think, that if echolocation was evolved, it is pretty much the same sort of patchwork common among species. If created, the gods must be mad.

doov

So in other words, though the idea of such complexity arising all by itself is ludicrous, you accept it because its implementation in nature doesn't fit your view of how God should create.

Doubting Didymus · 09-21-2003, 09:52 PM

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Originally posted by Charles Darwin
So in other words, though the idea of such complexity arising all by itself is ludicrous.

You say that so often. Why do you think that things can't arise without a creator, exactly? I don't think you've ever said.

Charles Darwin · 09-21-2003, 09:53 PM

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Originally posted by lpetrich
Charles Darwin:
(me on separate creators for members of a food chain...)
A god for this, a god for that. Obviously you are not the first one to have thought that one up.

So what? Doesn't it look like multiple designers at work? I am VERY skeptical of the hypothesis that a single designer was responsible for all those conflicting designs.

And evolution by natural selection accounts for all these conflicts VERY beautifully.

I don't begrudge you your religion. Your are VERY skeptical of the hypothesis that a single designer was responsible for all those conflicting designs. That is fine, I can't argue with you. For you evolution is a fact.

Charles Darwin · 09-21-2003, 09:57 PM

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Originally posted by DMB
Objections to evolution have been wholly religious in origin.

No, the objections are based on science.

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Originally posted by DMB
They hardly stack up against the massive body of evidence for evolution. Paley's watch? -- Come on. Eye's or wings are too complex to have evolved, because what use is half an eye or half a wing? -- Comprehensively flattened.

Really? I hadn't heard that.

Charles Darwin · 09-21-2003, 10:04 PM

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Originally posted by Doubting Didymus
That may be what the newer article posted by GFA is investigating, but if you reread the slightly older Kollar and Fisher abstract, you'll see that the reactivation of avian tooth genes is indeed the focus of the experiment.

That is in fact exactly what the conclusion of Kollar and Fisher is.

The abstract, again.

Quoth:
results suggest that the loss of teeth in Aves did not result from a loss of genetic coding for enamel synthesis in the oral epithelium but from an alteration in the tissue interactions requisite for odontogenesis.

That's a very clearly put message. Aves still have tooth genes, and they still work when they receive an appropriate signal. I can't access a full text copy from the web, but in the article the teeth themselves are described, and avian teeth are clearly present in the embryos.

Again, the Kollar and Fisher paper is sending a more relevant message. The evidence IS in the formation of avian teeth. The papers conclusion is that the enamel synthesis genes are still present in a working form in toothless aves, but that the cellular signals / developmental pathways needed to activate them are broken. (Have you ever studied basic cell biology, by the way? I'm sure you know about protein signal receptors and the like, yes?). The fact that a similar chemical signal can reactivate the avian genes and instigate the ontogenesis of avian teeth sends a fairly clear chemical signal towards me; modern aves once had teeth. What's your take on these results?

My take is that authors overstretched when they conclude the enamel synthesis genes are still present in a working form in toothless aves. The avian genes they refer to are building block genes used for all sorts of developmental purposes. It is no surprise that they are fully functional; they are used for a variety of purposes. Again, if there was some long since dormant avian set of genes being invoked then they should be riddled with mutations.

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