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NOT-SO-GREAT DEBATE THREAD. ROBINROHAN & FAITH ONLY, PLUS INVITEES
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Hey Faith, thanks again for my own emoticon.
If I'd known such a big fuss was going to be made over my slapdash addition of a grin to your sasqui, I'd have taken more pains over it and tried to come up with one that's more recognizable. But I am pleased that you appreciated the effort so much.
Anyway, back to business:
quote:
So may I now claim that mutation is sometimes a built-in mechanism and not random?
The language is so tricky when it comes to this topic, which is why many on the evo side simplify (or simply insist) mutation as random.
OK, that may partly explain why this discussion, which I've had other times here, gets so frustrating for me.
I see mutation as "a built-in mechanism" because it seems that DNA polymerases (the enzymes that copy DNA) are evolutionary optimized to make a few mistakes each generation.
(my bolding)
Thank you, that is the impression I keep getting from descriptions of how it works. I wonder if it's possible for this process to be made evident to me without a lot of effort and burying me in technical language. I know this has been discussed on other threads but I have to say that knowing the writer is only presenting evidence for his own evolutionist point of view I have a hard time trusting it besides having a problem following it. This is probably not the thread for getting too deeply into it but maybe another thread on the subject could be started eventually.
Some probably klutzy questions that have possibly been answered in those other discussions in a way I couldn't follow (or trust?) would be:
How many is "a few mistakes each generation?"
In how many species has this process been studied? (The nonscientist isn't thrilled with examples of bugs, plants and bacteria).
A DNA strand being so unbelievably long, (that is just one chromosome, right?), how is it even possible to make generalizations about the frequency of these mistakes? Do you just study one gene or short stretch of the DNA?
Given all the possible combinations of the chemicals G,C,T and A, to the untutored mind it seems that absolutely anything is possible if a mistake is made, but if there is a consistent pattern to these "mistakes" is there some rule that has been discovered that explains it?
Or, first, how much consistency or pattern is seen in these mistakes?
These are not sufficient questions, just a first stab at it, and I know I have more.
I have some recollection that there was a study done where scientists were able to reduce the error rate of a DNA polymerase beyond the already low rate provided by evolution's version. The idea is that if a species lineage evolved a "perfect" polymerase that didn't produce any errors/mutations at each generation, the species is unable to adapt, and so dies off as a result of their evolutionary dead-end. (I would take this with a grain of salt until I manage to produce a reference for you).
A reference may just lose me. That often happens. Sometimes it seems that a whole thread would be required to investigate just one such reference.
I don't understand, however, why so much weight is placed on these "mistakes" for adaptability. It is true that some traits have many genes, isn't it? Seems to me I've read that that is the case for instance with fur colors and patterns in domestic animals. But I can't seem to locate that link in my bookmarks any more. If many genes are available for just one trait, why isn't that enough to guarantee the variety that leads to adaptability?
If this is the case, that polymerases have evolved to make a few mistakes, than mutations are "a built-in process".
Terrif. Again my bolding. Of course as a creationist I want to reword this to say that
polymerases were created to throw out a few chemical alterations here and there according to some as-yet unknown rule or pattern. Unless some of this is a product of the deteriorating effects of the Fall. Depends on the results I guess. See, (Biblical) creationists have to think along both lines.
I see mutations as non-random - but others have argued with me that this view has to do with my definition of "randomness".
Are some of these arguments on EvC threads I could look up?
Let me explain how I see it: There are various mutational biases that cause some stretches of DNA sequence to be more prone to mutation than others.
Ah, "mutational biases." This is the sort of statement that makes me really want to learn what's involved in it, but my efforts usually just give out because I can't follow the technical language. This reference to biases showed up on Robin's first list from the Ernst Mayr book he's reading, as a proof of evolution. I see it differently of course.
On top of that, the type of mutation that will occur appears to be biased by the local DNA sequence. I see these biases as "non-random".
How exciting. Wish I could picture this better. Let me try to get it into my own words. You've got a "bias" along a stretch of DNA that makes mutations of any kind more likely, right? What exactly this bias is caused by, chemically speaking or whatever -- is that known? And besides that, there's something about that stretch of DNA that directs the type of mutation, which I guess is what you mean by "the local DNA sequence" -- you mean that something in the chemical arrangement of the very stretch that appears to be particularly subject to mutation also appears to direct the sort of mutation that can occur there? {AbE: That is, it somehow dictates the particular sequence (s) of T,C,A and G that can occur to the exclusion of others?)
However, there is no evidence that any type of sequence is mutation proof, or cannot experience a specific mutation. This means that all possible sequence changes are real possibilities for selection to act upon. In this sense I see mutation as "random", because it can change/produce any possible sequence combination.
BUT this COULD mean simply that study hasn't yet progressed to the point where possible patterns are recognizable, couldn't it? Questions: How many of these as yet random mutations occur as compared to the kind we are discussing where there appears to be some sort of rule or pattern involved?
Also, when the mutational biases act to produce a pattern, it is towards simple repetitive sequence instead of the sort of sequence that genes are made of - so it doesn't appear that the biases represent a gene-producing program. This is another reference I could dig up for you at some point.
Now this sounds like we are talking about something that really IS a mistake, that isn't helpful for variation or evolution at all, but something incoherent and useless, or am I not following you?
We all have been nicely nonadversarial in the thread, except for a few moments from each of us (though like you say they could be miscommunication). I took your "Creationist should research this" comment as more smug than it was probably intended. This has definitely been my most enjoyable interaction with you thus far.
It is nice to talk in a friendly way for a change. Wonder how long it will last. Of course if it happens at all that increases motivation to try to preserve it, so there's another plus. The creationist comment was to some extent a retort in that creationists are always being criticized for not doing real science, so if it appears that there might be an arena of investigation that could be important to them although not to evos (so that evos aren't as interested in studying it -- which is how I apparently misread what you were saying), then it would definitely be a path for creationists to take.
Hopefully you don't take my language as too pro-evo biased; if I state that something evolved as a fact (like I just did above), it is not because I am taking robinrohan's side in the argument, it is more because I am trying to state mainstream science's current understanding. I'm doing my best to stay neutral.
I appreciate that very much, thank you, and I'm all the more appreciative since I'm surprised that an evo would make such an effort.
If you are interested in those references I mentioned and I don't post them, please feel free to give me a reminder when I show up again in a week or so.
OK.
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NOT-SO-GREAT DEBATE THREAD. ROBINROHAN & FAITH ONLY, PLUS INVITEES
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This message has been edited by Faith, 12-22-2005 02:31 PM
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