|
Register | Sign In |
|
QuickSearch
Thread ▼ Details |
Member (Idle past 1488 days) Posts: 19762 From: Silver Spring, MD Joined: |
|
Thread Info
|
|
|
Author | Topic: Wells' Icons of Evolution - Peppered Moths | |||||||||||||||||||||||
John Paul Inactive Member |
Well I don't doubt that speciation occurs. Creationists since the time of Karl von Linne knew that the Created Kind was at least at the Genus level (Linne being a Creationist). However it could be that the definition of species is somewhat ambiguous... (OK, OK a new thread)
As far as the moths and NS I don't see where it wouldn't be an example of that. The environment changed and when it changed those organisms better suited to that new environment thrived (and became the majority) and those that thrived in the old environment were now the minority. Looks like I will have to go back and read that chapter in "Icons..." again to see what Wells really says. I'll be back...
|
|||||||||||||||||||||||
Percy Member Posts: 22480 From: New Hampshire Joined: Member Rating: 4.8 |
You might also take a look at Message 6 where Cromwell makes a lengthy argument and concludes that whatever the cause, it isn't NS. Cromwell draws upon arguments from Wells, but having not read Wells myself I don't know if Cromwell's conclusion agrees with him.
--Percy
|
|||||||||||||||||||||||
JonF Member (Idle past 190 days) Posts: 6174 Joined: |
Or have the affected alleles been identified? A reasonable question. I don't think that the actual mutations or genes have been identified. I could be wrong. There have been lots of breeding experiments (in the 60's and 70's by Clarke, Sheppard, Lees, Creed and Steward) with the peppered moth that have established that the difference between light and dark forms follows classic Mendelian genetic rules (with the dark form having a dominant allele that controls the expression of melanin in the wings) and three different alleles of the same gene that control variations of color in the lighter moths (if the dominant form is not present). (Somebody, I forget who, even tested for Lamarkian inheritance and failed to find any). The experiments indicate that, whatever the mutation actually is, it's a fairly common and recurring one. The fascinating thing is that the black form is a dominant allele; if a moth has it from either parent the moth is black. In the absence of strong selective pressure the black form would be common and maybe even dominate. But no black moths were observed before 1800 or so (and I know that there's a lot of possible effects there, but one way or another the black form was rare). The difference between light and dark moths is genetic, and whatever has caused the population color distribution to change is affected the hereditability of particular genes. Sounds like NS to me.
|
|||||||||||||||||||||||
JonF Member (Idle past 190 days) Posts: 6174 Joined: |
having not read Wells myself I don't know if Cromwell's conclusion agrees with him. You can read an earlier version of Wells' treatment of the peppered moth at Second Thoughts about Peppered Moths. I doubt that he chaned his conclusion much in the book. It appears to me that his major problem is with the staged photographs. At that URL, he writes:
quote: Note that date of his Harrison reference. IMHO he doesn't make his case that "the true causes of industrial melanism in peppered moths remain largely unknown". But others might disagree, incredible as that seems.
|
|||||||||||||||||||||||
Percy Member Posts: 22480 From: New Hampshire Joined: Member Rating: 4.8 |
Hi, JonF!
Can I assume that your mentions of mutation did not mean to imply that repeated and relatively contemporary mutations were the source of the color changes. A recent mutation would surprise me as a source of the changes, since I would have thought it far more likely that NS was operating on preexisting alleles already in the peppered moth genome, even though of course they originally arose, who knows when, by mutation. You mention that the changes were found to follow "classic Mendelian genetic rules", and this would seem fairly conclusive for NS to me. Actually finding the gene on a chromosome doesn't seem necessary, though it would provide an additional level of confirmation. --Percy
|
|||||||||||||||||||||||
JonF Member (Idle past 190 days) Posts: 6174 Joined: |
Can I assume that your mentions of mutation did not mean to imply that repeated and relatively contemporary mutations were the source of the color changes. Er, no. I don't remember all the details, and I can't locate anything conclusive on the Web right now, but I'm pretty sure that data incdicates that the mutation is one that happens over and over again. That's what keeps the black phenotype in the population in times when it's so strongly selected against. I'm not enough of a geneticist to understand why a particular mutation would be common. Perhaps there's a particular point in the DNA that's unstable?
|
|||||||||||||||||||||||
Percy Member Posts: 22480 From: New Hampshire Joined: Member Rating: 4.8 |
I guess I'd be surprised to learn that's the case. If you happen to run across more info let us know.
--Percy
|
|||||||||||||||||||||||
KCdgw Inactive Member |
quote: Some mutations occur more often than others because certain DNA sequences lend themselves to being miscopied or for substitutions to occur. Its primarily due to the physical structure of the DNA at those points and its interactions with molecules such as DNA polymerase, and others. In the case of the peppered moth, however, the rise in the melanic form is NOT due to recurring mutations, simply because the rate of recurrent mutation is nowhere near enough to account for the increase. KC
|
|||||||||||||||||||||||
zephyr Member (Idle past 4572 days) Posts: 821 From: FOB Taji, Iraq Joined: |
quote:May I ask for a minor clarification? Are you simply saying that the transition from ~0% dark moths to 98% dark is not accounted for by a recurring mutation that made each individual dark? Or do you mean that the rate of recurrence is so low that the dark moths were all likely the descendents of one dark mutant born in the 1800's?
|
|||||||||||||||||||||||
NosyNed Member Posts: 9003 From: Canada Joined: |
My understanding is that there are always some dark in the population. I don't know why. It may be that it is linked to something that is of some other benefit. It would be interesting to have more of the details.
|
|||||||||||||||||||||||
KCdgw Inactive Member |
quote: The former. KC
|
|||||||||||||||||||||||
John Paul Inactive Member |
http://www.arn.org/docs/wells/jw_pepmoth.htm
It looks like all Wells is saying that IF this story is an Icon of evolution scientists had better get the conclusion straight.
|
|||||||||||||||||||||||
KCdgw Inactive Member |
quote: Too bad Wells can't get even the data or methods straight, let alone the conclusion. KC
|
|||||||||||||||||||||||
JonF Member (Idle past 190 days) Posts: 6174 Joined: |
t looks like all Wells is saying that IF this story is an Icon of evolution scientists had better get the conclusion straight. Well, then, no problem ... we've got it.
|
|||||||||||||||||||||||
cromwell Inactive Member |
What conclusion have we come to?
Majerus and the studies in the U.S (Michigan,Pennsylvania e.t.c.)of the peppered moths are only observations of quantity sightings of the peppered moths. I was asked earlier to provide calculations on my assumptions that there wasn't enough "material" evidence... Quantity of moths predated upon,known number of polluted trees e.t.c.To show my reasons as to why i believe that natural selection was not the mechanism behind the melanic dominance due to a cryptic background.Resulting in one proliferation of a variant over another. I have no substantial calculations,because my assumptions were based on the observations of the Majerus,U.S. data and other data mentioned by Wells.They have not provided calculations either.I have admittedly surmised that this does not look like natural selection,but i'm not the only one surmising.Without indepth evidence is not everyone else surmising? The data by the scientists consists of only the number of observations and a pie chart by Majerus.There are NO calculations provided by these observers giving an indication of how many moths were victims of predation,amount of polluted trees,and yes the moths landed on the open parts of the trees(very rarely),but a major factor would be for how long they rested on the trees,time of day,weather conditions,observations of predators present and other insects seen on the tree trunks at the time and many other factors.This is hardly an indepth study.Surely as intelligent scientists you would want to know the whole picture before assuming that this is natural selection at work? I originally contested that this was not an icon of evolution.Is it really an icon? Is there really evidence that the mechanism behind variant changes in the peppered moth is by natural selection? Do the field studies truly bare this out?
|
|
|
Do Nothing Button
Copyright 2001-2023 by EvC Forum, All Rights Reserved
Version 4.2
Innovative software from Qwixotic © 2024