Majerus>>To end, may I put on record to you, that my view is that the rise
and fall of the carbonaria form of the peppered moth has resulted from
changes in the environments in which this moth lives. These changes have
come about as a result on changes in pollution levels which have altered
the relative crypsis of the forms of this moth. The main, if not the only
selective factor that has lead to changes in the frequencies of the forms
over time is differential bird predation. The case of melanism in the
peppered moth IS ONE OF THE BEST EXAMPLES OF EVOLUTION IN ACTION BY
DARWIN'S PROCESS OF NATURAL SELECTION that we have. In general it is based
on good science and it is sound. <<
Chadwick>>(At the risk of opening this can of worms again...)<<
You seem perfectly willing to get into the can when you think that you can
beat evolutionists over the head with it. Which is what this is really all
about.
Chadwick>> Well, Mr Majerus opinion is in. Just exactly how much data
does he have that birds are the principal predators? Check his data. <<
"Principle predators"? Why should they have to be the principle
predators? The questions are:
A) Do birds prey on the moths at all?
B) Is the birds selection biased due to differences in crypsis in the
moths?
The answer to both questions is yes.
Bats or spiders may be the "principle" predators of peppered moths as far
as total numbers go, but their hunting strategies do not rely on vision.
Therefore, the effects of their predation on the moth population would be a
wash with regards to cryptic coloration.
Majerus>> Evidence of selective predation in the peppered moth is not
lacking. It is just not provided in the quick text book descriptions of
the peppered moth. How can it be...Of all the people I know, including both
amateur and professional entomologists who have experience of this moth, I
know of none who doubts that differential bird predation is of primary
importance in the spread and decline of melanism in the peppered moth. <<
Chadwick>> That settles it. *All* agree that birds are the major
predators. Where are the data? If there were data, you can bet he would
not be citing so many opinions.... <<
First off as Kevin has pointed out this was an e-mail to Don Frack
clarifying his views, not a scientific paper.
So now, it is "major predators" is it? Again, why should they have to be
major predators? They don't have to be major predators to have a "major"
effect. They could be sixth or seventh down the list of peppered moth
predators as long as their selection of moth prey is biased in a way that
other moth predators isn't. i.e. by crypsis in the moths.
Grant>> Documentation of the decline in melanic frequencies is vastly more
detailed...No other evolutionary force can explain the direction, velocity,
and magnitude of the changes except natural selection. <<
Grant>> The interpretation that visual predation in a likely driving force
is supported by experiment and is parsimonious given what has been so well
established about crypsis in other insects. <<
Grant>> Majerus allows that the basic story is more complicated that
general accounts reveal, but it is also true that none of the complications
so far identified have challenged the role assigned to selective predation
as the primary explanation for industrial melanism in peppered moths. <<
Grant>> Even if all of the experiments relating to melanism in peppered
moths were jettisoned, we would still possess the most massive data set on
record documenting what Seawall Wright(1978) called "...the clearest case
in which a conspicuous evolutionary process has been actually observed."
Certainly there are other examples of natural selection. Our field would
be in mighty bad shape if there weren't. Industrial melanism in the
peppered moth remains one of the best documented and easiest to understand.
<<
Chadwick>> I rest my case. <<
I hope you are prepared for a summary judgement against your position.
By the way, you never answered my question. You clearly implied that any
evolutionist who still considered the case of the peppered moth to be a
valid example of natural selection in action was either ignorant or
uninformed. So again, I would like to know where you place Doctors Grant
and Majerus in this scheme.
Bye
Troy Britain (Amateur Naturalist)
"It is so easy to hide our ignorance under such expressions as the `plan of
creation,' `unity of design,' &c., and to think that we give an explanation
when we only restate a fact. Any one whose disposition leads him to attach
more weight to unexplained difficulties than to the
explanation of a certain number of facts will certainly reject my theory."
- Charles Darwin.