Original Message Follows:
=========================
evolution-digest Monday, February 15 1999 Volume 01 : Number 1302
----------------------------------------------------------------------
Date: Sat, 13 Feb 1999 20:58:12 -0700
From: PostMaster <Mailer-Daemon@navyouth.org>
Subject: Message Not Delivered: evolution-digest V1 #1301
The message you sent could not be sent to the following recipient(s):
SMTP:bgmsm@navyouth.org
Original Message Follows:
=========================
evolution-digest Sunday, February 14 1999 Volume 01 : Number 1301
- ----------------------------------------------------------------------
Date: Fri, 12 Feb 1999 21:36:11 -0700
From: PostMaster <Mailer-Daemon@navyouth.org>
Subject: Message Not Delivered: evolution-digest V1 #1300
The message you sent could not be sent to the following recipient(s):
SMTP:bgmsm@navyouth.org
Original Message Follows:
=========================
evolution-digest Saturday, February 13 1999 Volume 01 : Number 1300
- - ----------------------------------------------------------------------
Date: Fri, 12 Feb 1999 10:12:20 -0700
From: PostMaster <Mailer-Daemon@navyouth.org>
Subject: Message Not Delivered: evolution-digest V1 #1296
The message you sent could not be sent to the following recipient(s):
SMTP:bgmsm@navyouth.org
Original Message Follows:
=========================
evolution-digest Thursday, February 11 1999 Volume 01 : Number 1296
- - - ----------------------------------------------------------------------
Date: Wed, 10 Feb 1999 21:21:43 -0700
From: "Kevin O'Brien" <Cuchulaine@worldnet.att.net>
Subject: Re: Coconino trackways [was Flood Model and ichnofossils]
>
>Hi Troy,
>
>Welcome to the fray!
>
[snip]
>
>> If this material was deposited rapidly how is it that no unlucky, stupid,
>>or already dead animals managed to get buried in it? IOW why *only* trace
>>fossils in the Coconino?
>>
>That is a big question, whether it was deposited rapidly or slowly,
>subaerially or underwater.
>
Actually it's not so big. Deserts are notoriously poor in fossils because
the conditions do not allow for the long-term preservation of animal
remains. Few remains are buried deeply or long enough to give petrification
time to work, and there are few mechanisms by which petrification can
proceed.
>
>> All these things, reptile/mammal-like reptile tracks, spider & scorpion
>>tracks, the lack of body fossils, a sandstone made up of well sorted,
>>rounded quartz sand is perfectly consistent with a desert eolian sand dune
>>environment.
>>
>You believe that? I saw a diorama of that at a Grand Canyon visitor
>center, back in the 60's. That was before they knew very much about large
>submarine sand dunes, and ambulatory behavior of amphibians underwater, and
>the fact that the fossil tracks match underwater prints much better than
>dry, crumbly, wet or very wet sand ones.
>
Any competent geologist can spot the difference between a fossil sand dune
and a fossil sand bar, based partly on studies of modern sand dunes and sand
bars. The eolian nature of the Coconino sandstones was recognized in the
1930's, but modern research has verified that conclusion. There is no doubt
among geologists that the Coconino is made up of petrified sand dunes, not
petrified sand bars.
>
>> Why should anyone who is not defending a literalistic interpretation of
>>the Bible, accept the rather bizarre flood model for the origin of this
>>formation over the straightforward one?
>>
>Why? Because the tetrapod tracks, invertebrate tracks, lack of body
>fossils, and sandstone made up of well-sorted rounded quartz sand is
>consistent with a submarine sand dune environment.
>
This largely superficial description of the Coconino does not begin to
describe the evidence that demonstrates the eolian nature of the sandstone.
For an excellent review, see "Coconino Sandstone" by LT middleton, DK
Elliott and M Morales in _Grand Canyon Geology_ (1990), edited by SS Beus
and M Morales. It also includes a discussion of the sandstone's ichnology.
The authors conclude, among other things, that the trace fossils establish
that the sand had been very dry except for occasional moistening by rain or
dew. They report no evidence that the Coconino had been submerged at any
time in its history.
Kevin L. O'Brien
- - - ------------------------------
Date: Wed, 10 Feb 1999 20:29:22 -0800
From: Pim van Meurs <entheta@eskimo.com>
Subject: RE: Data non grata?
relevance perhaps ?
- - - - ----------
From: Vernon Jenkins[SMTP:vernon.jenkins@virgin.net]
Sent: Wednesday, February 10, 1999 3:09 PM
To: evolution@calvin.edu
Subject: Data non grata?
To the Forum:
I am encountering considerable difficulty in bringing the material of
the appended file into the public domain - where it surely belongs. Is
anyone able to explain the enigma? - or is it that I've overlooked
something important?
Vernon
<<File: Judging.html>>
- - - ------------------------------
Date: Thu, 11 Feb 1999 09:57:10 +0000
From: Tim Mitchell <t.mitchell@uea.ac.uk>
Subject: message not delivered
At 22:17 10/02/99 -0500, you wrote:
> To whom it may concern,
>
> I keep getting these "message not delivered: evolution-digest..."
>messages.
>
> Why?
>
> How do we make it stop?
>
> Thanks in advance.
>
> Bye
>
> Troy Britain (Amateur Naturalist)
>
I'm getting them too. These gratutious error messages have become a little
wearisome...
Tim
/// \\\
( 0 0 )
____oOO (_) OOo_________________________
Tim Mitchell
Climatic Research Unit
post: CRU, UEA, Norwich, NR4 7TJ, UK
email: t.mitchell@uea.ac.uk
web: http://www.uea.ac.uk/~f709762
phone: +44 (0)1603 593161
fax: +44 (0)1603 507784
__________________________________________
- - - ------------------------------
End of evolution-digest V1 #1296
********************************
- - ------------------------------
End of evolution-digest V1 #1300
********************************
- ------------------------------
Date: Sat, 13 Feb 1999 11:37:55 -0700
From: "Kevin O'Brien" <Cuchulaine@worldnet.att.net>
Subject: Re: old dna
Andrew wrote:
>Hi list,
>I was wondering if anyone has retrieved ancient DNA from amber insects or
>wooly mammaths or any old sources? Is this even possible? If some has been
>looked over what have we found that relates to evolution or maybe even the
>molecular clok rates.
>
Here are some review articles you might find interesting:
Hoss M. "Ancient DNA." _Horm Res_ (1995) 43:4, 118-120
Cano RJ. "Analysing ancient DNA." _Endeavour_ (1996) 20:4, 162-167
Audic S, Beraud-Colomb E. "Ancient DNA is thirteen years old." _Nat
Biotechnol_ (1997) 15:9, 855-858
Cooper A, Wayne R. "New uses for old DNA." _Curr Opin Biotechnol_ (1998)
9:1, 49-53.
They should have gobs of references you can review to give you a good
over-all picture of the state of the art so far.
Kevin L. O'Brien
- ------------------------------
Date: Sat, 13 Feb 1999 12:01:48 -0700
From: "Kevin O'Brien" <Cuchulaine@worldnet.att.net>
Subject: Re: old dna
Andrew wrote on 8th February:
> I was wondering if anyone has retrieved ancient DNA from amber insects or
> wooly mammaths or any old sources? Is this even possible? If some has been
> looked over what have we found that relates to evolution or maybe even the
> molecular clok rates.
Dave Tyler responding:
"Yes. This has been done and it has yielded much controversy. Some now
think that all DNA from amber is contamination - but this is by no means
agreed. A 1993 article pointing out the implications if the DNA is
genuinely present in these fossils is at:
http://www.pages.org/bcs/Bcs041.html Fossil DNA in amber and implications
for geological time."
The implications of that article are that DNA cannot last more than 10,000
years (40,000 at the outside), so if DNA is found in bones or insects
trapped in amber then the bones or insects must be at least 10,000 years old
and certainly no older than 40,000 years old, in the absence of a credible
explanation for how DNA can be preserved for millions of years.
I did a literature search last night using the Entrez MedLine database at
<http://www.ncbi.nlm.nih.gov/Entrez/medline.html>. I found not only the
review articles I reported to Andrew, but more. The current concensus
appears to be that in fact DNA cannot survive millions of years even in
amber [Austin JJ, Ross AJ, Smith AB, Fortey RA, Thomas RH. "Problems of
reproducibility--does geologically ancient DNA survive in amber-preserved
insects?" _Proc R Soc Lond B Biol Sci_ (1997) 264:1381, 467-474]. However,
new techniques have extended the age range for acquiring DNA from bone out
to 15,000 years and there are both handling techniques and tests that insure
that the samples are not contaminated. Ancient DNA analysis is now a
standard tool in molecular evolution for all samples less than 15,000 years
old. The recent recovery of DNA from Neandertal bones could push the
technique to even older ages. Given time, we might eventually be able to
acquire DNA from bones and teeth that are at least 100,000 years old, maybe
even a million. Whether we can go still farther back in age remains to be
seen.
Even so, for now at least, the implications reported on in the article Dave
cited are largely moot. There has been no unambiguous recovery of DNA from
any sample a million years old or older.
Kevin L. O'Brien
- ------------------------------
Date: Sat, 13 Feb 1999 12:25:51 -0700
From: "Kevin O'Brien" <Cuchulaine@worldnet.att.net>
Subject: Re: Cambrian Explosion
Art Chadwick wrote:
>
>I posted a couple of papers earlier tha I thought were worthy of comment.
>Kevin's recent discussion on the naturalistic imperative of science brings
>back to mind these statements on the origin of complex life forms. Since
>the sources were in the earlier communications, I simply include a couple
>fo crucial paragraphs for consideration
>
[snip to save space]
>
>Where will naturalistic science go with this?
>
I'll be quite frank, Art: I have no idea. However, I will not use my own
lack of imagination as evidence that a naturalistic explanation is
impossible. I seem to recall very similar kinds of arguments with regard to
bird and whale transitional forms, yet recent discoveries of both bird and
whale transitional forms have shown that arguments based on a lack of
evidence are quite fragile and prone to instant collapse once even just a
single piece of evidence is finally found.
The claim that the absence of evidence is in fact evidence of absence is in
fact a logical fallacy called the appeal from ignorance (a particular
proposition is false because it has not been proved true). To claim, or
even suggest, that the Cambrian lifeforms could not have evolved because no
has yet found fossilized ancestors is to engage in this fallacy. What I
would like to know is, are there any theoretical reasons why there cannot be
any Cambrian ancestors and what evidence do have (other than a lack of
fossils) that supports these reasons?
An alternative question would be, are there any theoretical reasons why we
would not expect to find any fossils (other than that the animals to make
those fossils never existed)? Perhaps the local population was too low in
that earlier time for enough fossils to be preserved for us to find millions
of years later. Maybe the descendents migrated into that area from
somewhere else where they evolved, and maybe the sediments of that other
place no longer exist or are currently inaccessible to us. Perhaps the
earlier conditions were not conducive to preserving fossils, despite the
similarity of the two groups of sediments. Perhaps the organisms that were
ancestral were even more delicate and couldn't stand even these very gentle
fossilization conditions. One can ignore these alternatives, but that does
not mean they are not viable.
Kevin L. O'Brien
- ------------------------------
Date: Sat, 13 Feb 1999 12:36:55 -0700
From: "Kevin O'Brien" <Cuchulaine@worldnet.att.net>
Subject: Re: Evaporites and rates
Greetings Karen:
>
>Dear Kevin,
>
>Your thoughts about rate are most interesting:
>
>
>>>What do you see as sure evidence for slow rates?
>>>
>>
>>The sheer thickness of the deposits (knowing that evaporation is a slow
>>process), the presence of alternating seasonal layers like tree rings, the
>>presence of different kinds of impurities deposited at different times of
>>the year forming descreet layers, the lack of significant amounts of
>>sediment mixed with the salt (which would have occurred if deposition had
>>been rapid), etc.
>>
>
>
>The great thickness --
>
>Knowing that evaporation is a slow process, and would presumably have to
>occur at about sea level, would you postulate a large coastal salt flat
>that gradually sank (or a sea level rise) at just about exactly the rate of
>the buildup of the salt?
>
Salt deposition doesn't have to occur at sea level, as the prehistoric
Mediterranean basin or the modern day Salt Lake and Dead Sea basins testify.
All you would need is a basin into which water flows but from which water
leaves only by evaporation. As long as evaporation is faster than inflow,
the basin will not fill up with water but will fill up with salt.
The scenario you outline, however, was used a couple of decades ago to
describe how the halite deposits in the Gulf of Mexico formed. I may not
have all the details right, but as I remember it this is how it went.
As the North American plate moved west the area that would become the Gulf
of Mexico and the southern United States stretched and weakened, developing
many small faults, most of which still exist east of the Mississippi valley.
The weakened crust sank until it dropped below sea level, but formed a
shallow shelf instead of a basin. Eventually it was covered by water, but
over the millions of years that followed tectonic and climatic changes
caused the shelf to be periodically exposed then resubmerged. With each
cycle (which did not remain constant but changed gradually as the conditions
changed) fresh salt would evaporate out on the exposed shelf, then be
covered with sediment when the shelf was inundated. In this way alternating
layers of halite and sediment could form that would show seasonal, climatic
and tectonic variation.
In this scenario both land level and sea level would rise and fall
independently of one another, to create the cycle of exposure and inundation
necessary to form the salt flats. Your description of this process would
imply a certain ad hoc quality to this uniformitarian explanation, but in
fact the interplay between land level and sea level is built into the system
and would occur as a natural consequence of the process. Besides, it wasn't
"exact". There were times when land rise coupled with sea fall left the
salt flats high and dry for a time, with no periodic inundation; there were
other times when land fall coupled with sea rise left the salt flats fully
submerged with no periodic exposure. Also, as more salt accumulated the
strain on the land increased, causing it to be further weakened and to be
pushed down by the weight of salt and sediment.
Though this process probably hasn't ceased completely, three events probably
changed it drastically. The first was when the weight of the accumulating
salt and sediment finally overcame the underlying crust and the area
subsided to form the Gulf of Mexico. This alone probably significantly
reduced both the number and extent of the cycles. Much of the southern
United States sank as well, but the second event was probably the
stabilization of this area by some of the same forces that were uplifting
the Rocky Mountains. The third event was the formation of river deltas that
gradually laid down enough deposits to fill in the sunken land. However,
these deposits are causing the underlying crust to sink further, such that
when a river shifts course to form a new delta, the old one gradually sinks.
>
>Why would the salt layers that had crystalized
>not re-dissolve when they went below sea level?
>
The salt layers would be in the form of dessicated, rock-hard halite. Only
the top-most layers composed of loose granular crystals would dissolve
before the halite deposits were covered by sediment.
>
>Or if it were inland salt flats, like we find in deserts today but larger,
>are you postulating that there would be so much salt in the surrounding
>hills, that the layers of crystalized salt would eventually reach 100 ft.
>thick, in a long period of time without any tectonic disturbances?
>
You seem to be suggesting that these salt flats were formed by salt being
eroded from out the hills and deposited by seasonal rains and run-off.
That's not how they formed. The vast majority were formed when large bodies
of water could no longer replace loss due to evaporation and so dried up,
leaving their salt behind. That's what happened in the Mediterranean basin
and at Lake Bonneville, and what is happening now at the Caspian Sea and the
Dead Sea.
>
>Alternating layers --
>
>Are you saying that yearly seasonal variation is the only possible
>interpretation of the observation of alternating abundances of the
>impurities?
>
No, I am saying it is the best explanation, especially since alternatives
based on flood models such as yours require so many ad hoc explanations to
make everything turn out just right.
>
>Lack of significant amounts of sediment --
>
>Do you really think _less_ sediment in the salt indicates _more_ time?
>
Compared with your rapid sedimentation flood model, yes. If I understand
right, your model would have supersaturated brines "precipitating" salt out
into sediment-laden water, so that it would be well mixed with the sediment.
When the sediment rapid deposited, so would the salt, producing not descreet
layers of "pure" halite between layers of salt-free sediment, but
salt-saturated sediments similar to sahbka. The uniformitarian model,
however, permits enough time for sediment-laden water to loose its sediment
(becoming "pure" water), then concentrate its salt by evaporation until the
water becomes saturated, at which point the salt starts to crystallize out.
As the water evaporates the salt dessicates, forming "pure" salt that
contains no coarse sediments, but can contain small amounts of plankton
and/or fine sediment that hadn't settled out yet. However, exposed salt
flats can be covered with fine wind-blown organic and inorganic debris, that
can in turn be covered with more salt. This tends to form various types of
alternating bands, the most obvious being the broad white bands formed
during dry seasons and the thin dark bands formed during wet seasons. In
any event, each layer of halite is covered either by more halite or by
sediment, thus you get layers of sediment-free halite between layers of
salt-free sediment, even after millions of years.
>
>What rate would be optimal for the least sediment (wind blown or
water-borne)?
>
Frankly, I don't know; equally frankly, I don't see that it matters. What
do you have in mind?
Kevin L. O'Brien
- ------------------------------
Date: Sat, 13 Feb 1999 14:18:08 -0800
From: "Arthur V. Chadwick" <chadwicka@swau.edu>
Subject: Re: Cambrian Explosion
At 12:25 PM 2/13/99 -0700, you wrote:
>The claim that the absence of evidence is in fact evidence of absence is in
>fact a logical fallacy called the appeal from ignorance (a particular
>proposition is false because it has not been proved true). To claim, or
>even suggest, that the Cambrian lifeforms could not have evolved because no
>has yet found fossilized ancestors is to engage in this fallacy. What I
>would like to know is, are there any theoretical reasons why there cannot be
>any Cambrian ancestors and what evidence do have (other than a lack of
>fossils) that supports these reasons?
How much evidence do we have for extraterrestrials? for purple people
eaters?
for men on mars? Do you think they are there? At some point the lack of
evidence does influence you in your thinking (unless I miss my guess). At
what point is that? Would it be when a hundred years of intensive
searching in the fossil record has yielded nothing? When the rocks in the
Precambrian are in every point just like those in the Cambrian, but without
fossils? When soft-bodied forms are found in abundance in the Earliest
Cambrian? There is no reason given the naturalistic presuppositions that
there should not be fossils in the Precambrian.
>
>An alternative question would be, are there any theoretical reasons why we
>would not expect to find any fossils (other than that the animals to make
>those fossils never existed)? Perhaps the local population was too low in
>that earlier time for enough fossils to be preserved for us to find millions
>of years later.
What is true for the Late Precambrian must be true for the Early Cambrian
as well. (It is profoundly not).
Maybe the descendents migrated into that area from
>somewhere else where they evolved,
Where might that have been? and with such a variety of forms, why were
they unable to migrate erlier, an why were they all contained in that place
or places?
and maybe the sediments of that other
>place no longer exist or are currently inaccessible to us.
That is a great explanation. But in order to be a scientific explanation,
it must have a way of being tested (and the fact that they were preserved
nowhere at all cannot count!) The question then becomes how did they get
from where they were to everywhere in the world at once without leaving a
fossil trail?
Perhaps the
>earlier conditions were not conducive to preserving fossils, despite the
>similarity of the two groups of sediments. Perhaps the organisms that were
>ancestral were even more delicate and couldn't stand even these very gentle
>fossilization conditions.
How then did they survive the rigors of the Precambrian world? We are
talking here about the relatives of every modern Phylum. How could they
all be that delicate until the beginnings of the Cambrian, then all
suddenly become preservable?
One can ignore these alternatives, but that does
>not mean they are not viable.
You are a very creative individual, Kevin. That is a trait I admire. I
think, though, in this particular case your creative energy is not well
spent. Have a good day.
Art
http://geology.swau.edu
- ------------------------------
Date: Sat, 13 Feb 1999 15:00:52 -0800
From: Pim van Meurs <entheta@eskimo.com>
Subject: RE: Cambrian Explosion
At 12:25 PM 2/13/99 -0700, you wrote:
>The claim that the absence of evidence is in fact evidence of absence =
is in
>fact a logical fallacy called the appeal from ignorance (a particular
>proposition is false because it has not been proved true). To claim, =
or
>even suggest, that the Cambrian lifeforms could not have evolved =
because no
>has yet found fossilized ancestors is to engage in this fallacy. What =
I
>would like to know is, are there any theoretical reasons why there =
cannot be
>any Cambrian ancestors and what evidence do have (other than a lack of
>fossils) that supports these reasons?
How much evidence do we have for extraterrestrials? for purple people
eaters? for men on mars? Do you think they are there? At some point =
the lack of
evidence does influence you in your thinking (unless I miss my guess). =
At
But the issue is that there is a claim that Cambrian life could not have =
evolved based on a lack of fossilized ancestors. There is more evidence =
for Cambrian life than for purple people eaters and for evolution being =
the guiding mechanism.
- ------------------------------
Date: Sat, 13 Feb 1999 17:47:00 -0800
From: "Arthur V. Chadwick" <chadwicka@swau.edu>
Subject: RE: Cambrian Explosion
At 03:00 PM 2/13/99 -0800, Pim wrote:
>But the issue is that there is a claim that Cambrian life could not have
evolved based on a lack of fossilized ancestors. There is more evidence for
Cambrian life than for purple people eaters and for evolution being the
guiding mechanism.
True; but not for Precambrian complex animal forms, and therein lies the rub.
- ------------------------------
End of evolution-digest V1 #1301
********************************
------------------------------
Date: Sun, 14 Feb 1999 07:48:18 -0800
From: "Arthur V. Chadwick" <chadwicka@swau.edu>
Subject: Peppered Moths again
Nature 396, 35 - 36 (1998)
Not black and white =20
JERRY A. COYNE=20
Melanism: Evolution in Action
by Michael E. N. Majerus
Oxford University Press: 1998. 338 pp. =A355, $105 (hbk), =A323.95, $45=
(pbk)
>From time to time, evolutionists re-examine a classic experimental study
and find, to their horror, that it is flawed or downright wrong. We no
longer use chromosomal polymorphism in Drosophila pseudoobscura to
demonstrate heterozygous advantage, flower-colour variation in Linanthus
parryae to illustrate random genetic drift, or the viceroy and monarch
butterflies to exemplify Batesian mimicry. Until now, however, the prize
horse in our stable of examples has been the evolution of 'industrial
melanism' in the peppered moth, Biston betularia, presented by most
teachers and textbooks as the paradigm of natural selection and evolution
occurring within a human lifetime. The re-examination of this tale is the
centrepiece of Michael Majerus's book, Melanism: Evolution in Action.
Depressingly, Majerus shows that this classic example is in bad shape, and,
while not yet ready for the glue factory, needs serious attention.
According to the standard textbook litany, before the mid-nineteenth
century, all B. betularia in England were white moths peppered with black
spots, a form called typica. Between 1850 and 1920, typica was largely
replaced by a pure black form (carbonaria) produced by a single dominant
allele, the frequency of which rose to nearly 100% in some areas. After
1950, this trend reversed, making carbonaria rare and typica again common.
These persistent and directional changes implied natural selection. In a
series of studies, this conclusion was verified by several investigators,
most prominently Bernard Kettlewell of Oxford.
According to these workers, the evolution of colour was caused by birds
eating the moths most conspicuous on their normal resting site -- tree
trunks. The increase in black moths was attributed to pollution
accompanying the rise of heavy industry. A combination of soot and acid
rain darkened trees by first killing the lichens that festooned them and
then blackening the naked trunks. The typica form, previously camouflaged
on lichens, thus became conspicuous
and heavily predated, while the less visible carbonaria enjoyed protection
and increased in frequency. After the passage of the Clean Air Acts in the
1950s, trees regained their former appearance, reversing the selective
advantage of the morphs. This conclusion was bolstered by a geographical
correlation between pollution levels and morph frequencies (carbonaria was
most common in industrial areas), and most prominently by Kettlewell's
famous experiments which showed that, after releasing typica and carbonaria
in both polluted and unpolluted woods, researchers recaptured many more of
the cryptic than of the conspicuous form. The differential predation was
supported by direct observation of birds eating moths placed on trees.
Finally, Kettlewell demonstrated in the laboratory that each form had a
behavioural preference to settle on backgrounds that matched its colour.
Criticisms of this story have circulated in samizdat for several years, but
Majerus summarizes them for the first time in print in an absorbing
two-chapter critique (coincidentally, a similar analysis [Sargent et al.,
Evol. Biol. 30, 299-322; 1998] has just appeared). Majerus notes that the
most serious problem is that B. betularia probably does not rest on tree
trunks -- exactly two
moths have been seen in such a position in more than 40 years of intensive
search. The natural resting spots are, in fact, a mystery. This alone
invalidates Kettlewell's release-recapture experiments, as moths were
released by placing them directly onto tree trunks, where they are highly
visible to bird predators. (Kettlewell also released his moths during the
day, while they
normally choose resting places at night.) The story is further eroded by
noting that the resurgence of typica occurred well before lichens
recolonized the polluted trees, and that a parallel increase and decrease
of the melanic form also occurred in industrial areas of the United States,
where there was no change in the abundance of the lichens that supposedly
play such an important role.
Finally, the results of Kettlewell's behavioural experiments were not
replicated in later studies: moths have no tendency to choose matching
backgrounds. Majerus finds many other flaws in the work, but they are too
numerous to list here. I unearthed additional problems when, embarrassed at
having taught the standard Biston story for years, I read Kettlewell's
papers for the first time.
Majerus concludes, reasonably, that all we can deduce from this story is
that it is a case of rapid evolution, probably involving pollution and bird
predation. I would, however, replace "probably" with "perhaps". B.
betularia shows the footprint of natural selection, but we have not yet
seen the feet. Majerus finds some solace in his analysis, claiming that the
true story is likely to be more complex and therefore more interesting, but
one senses that he is making a virtue of necessity. My own reaction
resembles the dismay attending my discovery, at the age of six, that it was
my father and not Santa who brought the presents on Christmas Eve.
Occupying a quarter of the book, the Biston analysis is necessary reading
for all evolutionists, as are the introductory chapters on the nature of
melanism, its distribution among animals, and its proposed causes. Majerus,
however, designed his book for both professional and lay readers, and this
causes some unevenness in the material. The Biston story is sandwiched
between less
compelling chapters, including long sections on the basic principles of
genetics and evolution, which can be skipped by evolutionists. Other
discussions, involving melanism in ladybirds and other Lepidoptera, as well
as the author's unpublished work on habitat selection, are full of
technical details that will overwhelm the lay reader. Unfortunately, most
of the work described is inconclusive; despite the widespread occurrence of
melanism, its evolutionary significance is nearly always unknown.
What can one make of all this? Majerus concludes with the usual call for
more research, but several lessons are already at hand. First, for the time
being we must discard Biston as a well-understood example of natural
selection in action, although it is clearly a case of evolution. There are
many studies more appropriate for use in the classroom, including the
classic work of Peter and Rosemary Grant on beak-size evolution in
Galapagos finches. It is also worth pondering why there has been general
and unquestioned acceptance of Kettlewell's work. Perhaps such powerful
stories discourage close scrutiny. Moreover, in evolutionary biology there
is little payoff in repeating other people's experiments, and, unlike
molecular biology, our field is not self-correcting because few studies
depend on the accuracy of earlier ones. Finally, teachers such as myself
often neglect original papers in favour of shorter textbook summaries,
which bleach the blemishes from complicated experiments.
It is clear that, as with most other work in evolutionary biology,
understanding selection in Biston will require much more information about
the animal's habits. Evolutionists may bridle at such a conclusion, because
ecological data are very hard to gather. Nevertheless, there is no other
way to unravel the forces changing a character. We must stop pretending
that we understand the course of natural selection as soon as we have
calculated the relative fitness of different traits.
Jerry A. Coyne is in the Department of Ecology and Evolution, University of
Chicago, 1101 E. 57 Street, Chicago, Illinois 60637, USA.
Art
http://geology.swau.edu =20
------------------------------
Date: Sun, 14 Feb 1999 11:22:44 -0800
From: Pim van Meurs <entheta@eskimo.com>
Subject: RE: Cambrian Explosion
Let me see if I understand the whole issue. Data (speculations based on =
data) suggest that there was no Cambrian explosion after all, other data =
(such as fossils) do not (yet) support this idea. So there appears to be =
a conflict. The fossil data might be complete and the speculations are =
wrong or the fossil data is incomplete and the speculations are right. =
Both positions are based on a scientific approach, unlike the purple =
monsters you alluded to.
- ----------
From: Arthur V. Chadwick[SMTP:chadwicka@swau.edu]
Sent: Saturday, February 13, 1999 5:47 PM
To: evolution@calvin.edu
Subject: RE: Cambrian Explosion
At 03:00 PM 2/13/99 -0800, Pim wrote:
>But the issue is that there is a claim that Cambrian life could not =
have
evolved based on a lack of fossilized ancestors. There is more evidence =
for
Cambrian life than for purple people eaters and for evolution being the
guiding mechanism.
True; but not for Precambrian complex animal forms, and therein lies the =
rub.
Art
http://geology.swau.edu =20
------------------------------
Date: Mon, 15 Feb 1999 08:28:10 +1030
From: Mark Phillips <mark@ist.flinders.edu.au>
Subject: Re: Cambrian Explosion
> The claim that the absence of evidence is in fact evidence of absence is in
> fact a logical fallacy called the appeal from ignorance (a particular
> proposition is false because it has not been proved true). To claim, or
> even suggest, that the Cambrian lifeforms could not have evolved because no
> has yet found fossilized ancestors is to engage in this fallacy.
While I agree that we have to be very careful about discounting a
theory, just because there is a portion of evidence not yet found, I
don't think I can agree with your logical falacy point.
Absence of evidence may or _may_not_ be evidence of absence. Suppose
you have a million holes in the ground, and you want to see if at
least one of them contains a marble. You examine 200,000 holes at
random and find no marble. This is good evidence that, if there are
any marbles at all, their number is quite small. It is not however
enough evidence to conclude that there are no marbles at all. If
however you examined 950,000 of the holes and still there were no
marbles found, it would be strong evidence that are no marbles. My
point is that it is possible, at least in principle, to use absence of
evidence as evidence for absence.
I don't believe the "lack of pre-Cambrain fossils argument" correctly
matches the "appeal from ignorance" logical falacy. If no one had
bothered to look for fossilized Cambrian ancestors, and then somebody
claimed that because there were no such specimins they hadn't evolved,
_then_ this would be an appeal from ignorance falacy. But the fact
that people have been looking without success, is admissible evidence.
Don't get me wrong, it may well be that this evidence is ineffective
in discounting evolution. Perhaps ancestors were soft bodied, making
fossilization near impossible --- for example. But my point is that
the reason for the ineffectiveness has nothing to do with "appeal from
ignorance" logical falacy.
Mark.
_/~~~~~~~~\___/~~~~~~\____________________________________________________
____/~~\_____/~~\__/~~\__________________________Mark_Phillips____________
____/~~\_____/~~\________________________________mark@ist.flinders.edu.au_
____/~~\HE___/~~\__/~~\APTAIN_____________________________________________
____/~~\______/~~~~~~\____________________________________________________
__________________________________________________________________________
"They told me I was gullible ... and I believed them!"
------------------------------
Date: Sun, 14 Feb 1999 19:36:28 -0800
From: "Arthur V. Chadwick" <chadwicka@swau.edu>
Subject: RE: Cambrian Explosion
At 11:22 AM 2/14/99 -0800, you wrote:
>Let me see if I understand the whole issue. Data (speculations based on
data) suggest that there was no Cambrian explosion after all,
No. I know of no data that suggests that. A comparison of differences
between modern organisms at the genetic level, using the most sophisticated
techniques available has suggested that IF naturalistic evolution is the
explanation for origins, then the fossil record of the first complex animal
forms, including many soft bodied forms, in excellent preserved condition
cannot represent the early history of complex life forms on the earth; i.e.
the fossil record does not anywhere near represent the true evolutionary
history of life on earth, and we should find a billion years of fossil
record in the Precambrian preceding the first appearance of the metazoan
fauna of the Cambrian.
other data (such as fossils) do not (yet) support this idea.
Yes that is correct.
So there appears to be a conflict. The fossil data might be complete and
the speculations are wrong or the fossil data is incomplete and the
speculations are right. Both positions are based on a scientific approach,
unlike the purple monsters you alluded to.
Speculations about the existence of extraterrestrials are so far at least,
relegated to the realm of science fiction. Perhaps that is where the
speculations based upon the extrapolation of modern life forms a billion
years before the first metazoan fossil organism belong also. It is at
least overreaching the data by a billion years.
Art
http://geology.swau.edu
------------------------------
End of evolution-digest V1 #1302
********************************