Life Technologies
Life Technologies

Mighty Moth Man

An evolutionary biologist’s posthumous publication restores the peppered moth to its iconic status as a textbook example of evolution.

By | May 1, 2012


SALT AND PEPPER: Camouflage is the key to peppered moth predator avoidance.
SALT AND PEPPER: Camouflage is the key to peppered moth predator avoidance.

It must have seemed terribly ironic to late University of Cambridge evolutionary biologist Michael Majerus, after dedicating nearly half a century to the study of peppered moths (Biston betularia), that in the late 1990s his name became central to an increasingly contentious campaign to strip the peppered moth of its status as the prime example of Darwinian evolution in action.

It’s a well-known story: The moth’s ancestral typica phenotype is white with dark speckles. In the decades following the Industrial Revolution, a new, soot-colored form, known as carbonaria, flourished and displaced the typica moths in the heavily polluted woodlands of Europe.

Although scientists hypothesized as early as 1896 that the increase in carbonaria frequency could be explained simply by the fact that soot-covered tree barks camouflaged the dark-colored moths against predation by birds, it wasn’t until the 1950s that an Oxford University lepidopterist named Bernard Kettlewell performed the key experiments that provided persuasive evidence that bird predation was indeed the selective agent at work.

Kettlewell placed live carbonaria and typica moths on tree trunks in polluted and unpolluted woodlands in the U.K. and counted how many of each type survived predation. Moths with a coloring that blended better with the tree trunks survived in greater numbers.

But beginning in the 1980s, peppered-moth experts, including Majerus, began noting flaws in Kettlewell’s experimental designs. The most serious of these was that limited research into peppered moth behavior seemed to suggest that tree trunks were not the insect’s preferred resting place. That alone threatened to put a serious dent in the validity of Kettlewell’s setup—and in the bird predation theory itself.

In his 1998 book, Melanism: Evolution in Action, Majerus discussed these shortcomings in the context of a critical dissection of all the peppered-moth case evidence that had accumulated.

MOTHS ON TREES:  Majerus confirmed that wild moths (typica above and carbonaria below) did indeed rest on tree trunks.
MOTHS ON TREES: Majerus confirmed that wild moths (typica above and carbonaria below) did indeed rest on tree trunks.

For Jerry Coyne, a University of Chicago evolutionary biologist who had been teaching the case to university students for years, learning that “Kettlewell’s experiments weren’t really that carefully done” came as a shock, he says. In a review of Majerus’s book, published in a November 1998 issue of Nature, Coyne concluded that “for the time being we must discard Bistonas a well-understood example of natural selection in action.”

Coyne’s review dismayed Majerus, who, despite his criticisms, did believe there was strong evidence to back the case for the peppered moth as evolution’s poster child.

In no time, the popular media as well as the creationist movement pounced on the review, calling the classic peppered moth story “fraudulent,” a “blunder,” and an “embarrassment” to science. Even The Scientist contributed to the hysteria, publishing a 1999 opinion piece by then-cell biology postdoc and current intelligent design advocate Jonathan Wells on rethinking the peppered moth story.

“Through innuendo and through public smear campaigns, this case study was put into disrepute undeservedly,” says Ilik Saccheri, an evolutionary biologist at the University of Liverpool.

Not one to shy away from controversy, Majerus was nonetheless distressed by the fallout from Coyne’s book review. “[Majerus] was a cocky bastard,” says Laurence Cook, a retired geneticist from the University of Manchester. “He liked to have arguments of this kind around. But I think he did feel, because what he had written had been misinterpreted, that it was up to him to try and put it right.”

And that’s exactly what, in 2001, Majerus set out to do.

Over the course of 7 years, Majerus systematically recorded the fates of 4,864 peppered moths released into a 2.5-acre plot of unpolluted rural land in Cambridgeshire, U.K.

This time, instead of artificially placing the moths on tree trunks during the daytime, as Kettlewell did, Majerus released the moths within the hour before sunset into netting sleeves set up around the lateral branches of trees—which, through years of observation, he had identified as the moth’s preferred resting site. (He somewhat vindicated Kettlewell by observing that wild moths could in fact be found resting on trunks at least a third of the time.)

Majerus would then leave the moths to flutter about inside the enclosure throughout the night, removing the netting only after sunrise, when the moths were already settled in their resting positions for the day. After 4 hours or so, he counted the number of moths that were still at their resting sites. Those that were missing were presumed eaten. He also saw some of them being eaten by birds.

The results of his ambitious predation experiment showed that, in the unpolluted parkland of Cambridge, carbonaria moths had a daily survival rate 9 percent lower than that of their light-colored kin. This was significant enough to explain rapid directional changes in color frequencies.

In 2007 Majerus presented his results at a conference in Uppsala, Sweden. But before he could publish them, he passed away from a sudden and aggressive case of mesothelioma in 2009.

After realizing that Majerus’s results would not be published, Cook, Saccheri, and evolutionary biologists James Mallet from University College London and Bruce Grant from the College of William and Mary published the detailed account of Majerus’s work in the journal Biology Letters in February (Biol Lett, doi:10.1098/rsbl.2011.1136, 2012). “We really felt that we had a duty to try and make sure that all his efforts were not wasted,” Cook says.

Upon seeing Majerus’s results in a peer-reviewed journal, Coyne resumed teaching the peppered moth story after a 14-year hiatus. “He did everything he needed to do to take care of the problems in Kettlewell’s experiment,” he says.

Correction (May 4, 2012): This story has been updated from its original version to correctly state that Kettlewell used only live moths in his experiments, not live and dead moths as originally stated. The Scientist regrets the error.


Add a Comment

Avatar of: You



Sign In with your LabX Media Group Passport to leave a comment

Not a member? Register Now!

LabX Media Group Passport Logo


Avatar of: Woody Benson

Woody Benson

Posts: 1

May 4, 2012

Six decades have passed since Kettlewell undertook his first-of-a-kind experiment designed as a test for natural selection in the field.
However, even after all that time, it still seems hard for people to get things straight.

Author Luiggi incorrectly states that Kettlewell used a mixture of dead and living moths in his field experiments: they were all living moths sampled by trapping.
She also confuses things stating that there existed a design flaw in that independent research suggest[ed] that tree trunks were not the insect's preferred resting place. In other words, Kettlewell put out moths exclusively on tree trunks under the illusion that this was where moths preferred to rest. Luiggi gives credit to Majerus, saying he "somewhat vindicated Kettlewell by observing that wild moths could in fact be found resting on trunks at least a third of the time."

However, Luiggi is roundly wrong. Kettlewell did not assume that moths rested exclusively on tree trunks. In the first paper in 1955 he states early on that "the moth rests on tree trunks and boughs." A few pages later he affirms that in the experiments "boughs and trees [were] selected for release-sites." Kettlewell additionally clarifies that each experimental moth "was shaken from its box on to the bough or trunk" where they briefly "wandered about" until finding a good spot to rest. Finally, in his discussion, Kettlewell explains: "To the obvious criticism that the releases were not free to take up their own choice of resting site for the first day, I must answer that there were no other alternative backgrounds available for an insect that has to spend its days on trunks and boughs in this wood."

In the 1956 paper Kettlewell flatly affirms that "trunks and boughs" are the "normal resting places" of his moths. This is said with the authority of one who knows the biology of the species. Kettlewell was an accomplished field naturalist and moth specialist. His critics seem to be ignorant of Kettlewell's competence, and are poor readers to boot.
Majerus in his 2009 review paper for Evolution Education and Outreach says "[s]everal workers have [. . .] cast doubt on whether peppered moths usually spend the day on tree trunks. Curiously, he never mentions that Kettlewell never said, implied or conducted his experiment under the premise that they did so. Those others who cast doubt apparently equally did not understand Kettlewell's clear English, if indeed they actually read his papers. The creepy creationist fraud Jonathan Wells (who actually seems to have read Kettlewell's papers) also implies (dishonestly?) that Kettlewell did not put out moths on boughs. Most inexplicably, Majerus in the 2009 review mentioned above, after noting that Kettlewell watched flying moths settling on boughs, unjustly derides him for being lazy, saying "It seems likely, therefore, that the reason that Kettlewell released his moths onto tree trunks was simply experimental expediency: on tree trunks, it would be easier to see what was going on." This affirmation is misleading on at least two grounds. Kettlewell did not return to the trees to collect data after moths were set out surviving moths were censused by trapping at night. Second, Kettlewell released moths both on branches (boughs) and trunks because he knew that they used both, and said so.
Majerus made a quantitative survey of perched moths and found that 50% were on boughs and 37% on tree trunks. In other words, Kettlewell correctly placed his experimental moths in the places he knew they by and large preferred. No flaw existed with regard to moth placement Majerus merely confirmed the validity of Kettlewell's expertise and procedure.

Avatar of: James Mallet

James Mallet

Posts: 2

May 4, 2012

Dr Woody Benson is a man I admire greatly, and he makes some very good points here. He clearly knows the topic and its literature well. In general I wholeheartedly agree with him that criticisms of Kettlewell have been overblown.

However, I fear that by criticising Luiggi's enjoyable and brief overview of the recently published Majerus work (Cook et al. 2012 "Selective bird predation ...") in such strident terms, he is in effect shooting the messenger. It was the scientific literature, especially Majerus's 1998 book "Melanism" and Jerry Coyne's review of that book in 'Nature' that cast the doubts on the validity of Kettlewell's experiments. These problems led Majerus to design experiments that answered what were, in his view, flaws in earlier experiments, including those of Kettlewell.

If Luiggi is perpetrating myths, they are myths that we scientists ourselves developed and should have debunked long ago. I don't think we can expect a journalist to have encyclopaedic knowledge of all the scientific background papers on a topic (in this case, stretching back nearly 60 years ago); for that she will typically use the recent material with which she is supplied, and also infer what the story is from interviews. As one of the interviewees, to whom Luiggi sent the draft story before publication, I feel myself to blame for any errors in her story. I'll therefore answer each one of Dr. Benson's points.

Did Kettlewell use living and dead moths? In his 1955 and 1956 experiments, Kettlewell used only living moths. So Benson is entirely correct that Luiggi's piece gets this wrong.

However, many other later experimenters did use dead moths in predation experiments. In the Cook et al. 2012 "Selective bird predation ..." article Luiggi was reviewing, is the statement "Mark recapture studies of live moths, as well as many bird predation experiments using dead moths pinned to tree trunks, supported the hypothesis that birds were the agents of selection on melanism [3,9]." Ref. 3 is to Laurence Cook's 2003 review and meta-analysis of all the many tens of experiments that had been done (in Quarterly Review of Biology), and ref. 9 is to Kettlewell's 1955 paper.

So Luiggi's mistake is entirely understandable, and I should have caught her error when sent the draft article for fact-checking. I apologise for not catching it.

Did Kettlewell place moths on trunks only, or on trunks and boughs? I have to say I was myself surprised to learn that Kettlewell placed the moths on boughs as well as on trunks, even though I'd reread Kettlewell's papers many times, and used his results in teaching for years. But as Benson correctly shows, Kettlewell was a great naturalist, and well aware that peppered moths rested on boughs, as well as trunks. Benson is also correct that Kettlewell did release the moths on boughs, as well as on trunks.

However, although Luiggi says that "Kettlewell released moths on tree trunks", and that this "threatened to put a serious dent in the validity of Kettlewell's setup," she obtained these ideas directly from the literature she had read. Again from Cook et al. 2012 (electronic supplement 1) : "In his experiments Kettlewell often used high densities of reared insects. These were placed on tree trunks and observed, or marked, released and subsequently recaptured ... These procedures all have potential drawbacks".

So it's easy to see why Luiggi, and indeed anyone else might have been misled. Furthermore, Kettlewell (1955, 1956) himself is somewhat ambiguous about whether he released on trunks, or on trunks and boughs; he often seems to use "trunks" as shorthand for "trunks and boughs" in his text. His photographic plates also show moths on trunks, not boughs [see transcribed extracts, below].

Moreover, the idea that Kettlewell only released on trunks, and that this was a "flaw" in his experiments seems to have been mainly promoted by Majerus himself, especially in his 1998 book. Once again, I think that this misunderstanding cannot be blamed on Luiggi.

Other "flaws" in Kettlewell's experiments? I have long been of the opinion that none of the supposed flaws in Kettlewell's pioneering experiments were very grave, and I wrote to Majerus at the time suggesting he should have been more careful with his criticisms.

But others disagree. Jerry Coyne has always stoutly defended his own more extreme attack on Kettlewell's methodology in his book review. However, Dr. Coyne has never specified what he thought the actual flaws in Kettlewell were, and he seems to have ignored all of the other experiments in many different places and by many scientists on the same topic -- a vast weight of data overall, all pointing clearly in a single direction. The bird predation explanation is not dependent on Kettlewell's experiments alone. The totality of data were to myself and Laurence Cook (2003, see above), as well as to Majerus himself, together highly convincing evidence for the bird predation explanation of melanism.

Both boughs and trunks are characterised by having bark and lichens, and are similarly coloured, so that problem (which, as Benson shows, was not in fact even a problem with Kettlewell's experiments), has never seemed a big issue with me.

So was the new Majerus experiment strictly unnecessary? In my view, it was; and this also appears to be Benson's view. It was "proving the bleeding obvious" as we say in the UK.

However, by addressing so many of the supposed or real "flaws" of earlier work that he himself and others had raised, and also by performing the biggest ever experiment on the topic, Majerus has done us all a great service.

Transcriptions of some of Kettlewell's actual text from the original online PDF documents.

Kettlewell 1955:

p. 324:
It was noticed (i) that the species affected by this phenomenon [industrial melanism] rest fully exposed on tree trunks,walls or fences, apparently protected from predators by a concealing pattern.

p. 325:
By day the [peppered] moth rests on tree trunks and boughs, on which it takes up its position at dawn.

p. 326:
[in: Method of Scoring the Moths on their Backgrounds; this was for his experiment, validated by an independent score from noted animal behaviour professor Robert A. Hinde]

After making the initial decision at two yards, if the insect was judged "conspicuous" one walked away from it until a point was reached where it became inseparable from its background, be it carbonaria on lichen covered oak trunk in Devon (50 yards), or a typical betularia on a Birmingham oak trunk (40 yards).

p. 327:
[in: Results of Scoring Moths on Their Backgrounds]

The same method of scoring was used for both aviary and field experiments, the insects being released on trunks of different species of trees relative to their proportions within the wood.

[but later on on the same page he says:] Thus 651 male and female betularia were released in a circumscribed wood in the Birmingham district, where the melanic form comprised about 90 per cent, of the population. These consisted of 171 typical, 416 carbonaria, and 64 insularia. There were 33 release points, being the trunks and boughs of three birch trees and thirty oaks.

p. 328
[in: Aviary Experiments (i) General Features of the Aviary]

The supports of the cage were made of dark larch and spruce trunks with the bark still present. There were 13 of these and in addition 20 other resting sites were introduced, making 33 in all (15 light and 18 dark). There were also four horizontal poles. All the original construction trunks could be referred to as being lichen-free and with dark coloured bark, but among the introduced "furniture" birch and lichened trunks were included, and as variable an assortment of natural backgrounds as possible. The three forms of betularia were released on these.

p. 332:
[in: Experimental Releases in an Industrial Area: (ii) Method of Release]

In all the experiments, whether in the field or the aviary, boughs and trees selected for release-sites, were each given a number. In the wood, the proportion of such trees belonging to different species bore direct relationship to their estimated frequency in the locality.

Kettlewell (1956)

p. 287:
[in: Previous Experiments]

(a) When released on to available trunks and boughs, their normal resting places, over 97 per cent, of carbonaria (the black form) appeared to the human eye to be inconspicuous....

p. 293
[in: Direct Observation]
It became increasingly obvious that one was passing over the typical form on the lichened tree trunks, and they are practically impossible to see. ... The cryptic efficiency of the typical on a lichened background is, in fact, greater than that of carbonaria on the blackened Birmingham tree trunks.

p. 296:
The result was that I produced a high concentration of moths on comparatively few tree trunks (an average of 4 per tree), nor were the two forms on every occasion released in equality per tree.

p. 298:
It [the act of predation] involves, apart from insect cryptic efficiency, such other considerations as insect density, bird conditioning, and searching intensity per trunk, stimulated by an immediate previous experience of finding a conspicuous insect.

p. 298:
The "other method" of release referred to was used successfully on 18th June. This took place just before sunrise, between 4 and 4.30 a.m. Forty-two carbonaria, 65 typical (and 3 insularia) were allowed to fly out of their separate boxes which had been previously warmed on the engine of my car. The majority flew and took up positions on the boughs and trunks of nearby trees.

Plate I
FIG. 1. --Typical belularia (left) and its melanic carbonaria (right) at rest on lichened tree trunk, Deanend Wood, Dorset.
FIG. 2. --Typical betularia and its melanic carbonaria at rest on lichen-free tree trunk near Birmingham.
FIG. 3. --Song Thrush, Turdus ericetorum L., examining tree trunks from the ground with a carbonaria in its beak.

Plate II
FIG. 1. --Nuthatch, Sitta europera L., in the act of taking typical betularia from lichened tree trunk, Deanend Wood, Dorset. This species took 40 carbonaria to 11 typical while under observation.<
FIG. 2. --Spotted Flycatcher, Muscicapa striata L., about to take carbonaria from oak trunk, Deanend Wood, Dorset. This species was seen to take 81 carbonaria to 9 typical.
FIG. 3. --Robin, Erithacus rubecula L., with carbonaria in its beak taken from lichened tree trunk,Deanend Wood, Dorset. There were 3 typicals on this trunk at the moment of this photograph being taken. This species took 52 carbonaria to 2 typical whilst being watched.
FIG. 4. --Yellowhammer, Emberiza citrinella L., searching tree trunk, Deanend Wood, Dorset. A pair took altogether 20 carbonaria and on no occasion whilst under observation did they discover the typical form which, on every occasion, was offered in equal numbers to the black.

Avatar of: Nick Matzke

Nick Matzke

Posts: 1

May 4, 2012

Thanks very much for the story and the detailed responses. What I've never understood is why so many people seem to think it is obvious that it would have been a huge deal if the moths didn't typically rest on tree trunks.

Is the argument supposed to be that the backgrounds are different? But lichens grow on both trunks and boughs.

Also, the soot fallout (this was the original meaning of "fallout", i.e. black soot particles falling from the sky, blackening everything) would get to both places. (Soot both kills lichens and physically darkens the surfaces it lands on

Is the argument supposed to be that birds hunt on trunks, but not on boughs? But that's clearly ludicrous. Birds can fly, after all.

I think Majerus's point in his 1998 book was, in part, to critique the simplified textbook accounts, where "moths on trunks" had become the summary description. That this was oversimplified was worth pointing out, but then all textbook accounts of everything are oversimplified. Some textbook simplifications are misleading in a damaging way, but it is hard for me to see an argument that the trunks vs. trunks + branches issue deserved to be made into A Big Deal.

I suspect that what happened with the peppered moth was a "perfect storm" of various factors -- e.g.

1. the public and journalists, and not a few scientists, have gotten so used to the "textbook orthodoxy is wrong" line that they will enthusiastically accept and promote such claims, without sufficient examination. It's almost as if some people think that the more well-known some textbook account is, the more likely it is to be wrong.

2. Coyne's review of Majerus was clearly influenced by a 1998 article by Ted Sargent, who apparently had an ax to grind against the peppered moth example for some very weird (Lamarckian) reasons, although this wasn't apparent in the 1998 article.

3. Kettlewell was one of the first people ever to do experiments measuring selection in the wild and the lab. 50 years later, a whole field doing this has grown up, and along with this seems to have come a bias among experimentalists (like Coyne) that the old work must be bad. As far as I can tell, Kettlewell's work actually wasn't sloppy or poor, it just had limitations and oversights as almost any experiment done in the wild would have, particularly the first tries at it. The problems deserve to be pointed out, and further experiments should be done (and were done), but this is just normal science, not justification for a freakout.

4. The real story actually isn't that amazingly complicated, but it takes quite a bit of reading of the primary literature to get right, which is more than most people have time for.

5. Creationists shouted "fraud" as loud as they could, and some assumed that where there was smoke, there must be fire.

...and probably many other factors. The bizarre thing is that it went so far in the case of the peppered moth. The moths were removed from many textbooks, and by 2002 the journalist Judith Hooper was alleging that Kettlewell literally faked his data to please E.B. Ford, a theory made up out of thin air based on nothing more than the strong prior suspicion that Kettlewell Was Definitely Wrong Although I Can't Quite Say Exactly Why. It's almost like a case of mass hallucination or crowd psychology, except in the domain of popular science/science education.

Avatar of: Liti Haramaty

Liti Haramaty

Posts: 1457

May 8, 2012

Moths are cool organisms! check out the new global project - It's about moths and biodiversity and everyone can participate.

Avatar of: Guest


May 11, 2012

(Edited by poster, in hopes of being more clear.)

Regardless of whose work provides duplicable observations or experimental findings, I have questions of interpretation as to what is "proved" by those findings.

Both peppered moths and Galapagos area finches appear to have built-in genetic characteristics which are, and which remain, in place as changes in their local milieu favor first one potential morphological mode of expression, and then another. Perhaps if some strong environmental change were to favor left-handed humans and disfavor right handed humans for a few centuries, we might develop a predominantly left-handed population; and then, if things turned back the other way for a few additional centuries, we might go back to what many deem today to be "the norm" for handedness.

One of the issues I have with many articles (perhaps not written by research biologists, but by theorists who cite data the researchers find) is that some seem to imply -- and even sometimes to declare -- that a species has changed in some manner a or b or c, BECAUSE situation x or y or z required it. Correct me if this is wrong, please, but has anyone uncovered a mechanism whereby gametic cells receive signals from somatic cells, informing them a particular mutation is in order, BECAUSE its getting hard to compete out here in the current milieu? Most mutations are deleterious, by far. Some mutations are benign. Fortuitous mutations are exponentially rare. And specific need-based fortuitous mutations, although an abundance of circumstantial evidence indicates such MUST have occurred many times in many species over, say, the past hundred million years or so... have almost never been demonstrated in research, have they?

That Earth is some 4-plus billions of years old seems quite evident to me. That bilaterians existed as long ago as thirty million years during the Cambrian radiation does not trouble me. But, on the other hand, many hotly argued details of the current narrative of life origins strike me as somewhat forced and speculative (no more forced than some meta-science dogmas do, mind you, but forced on their own merits). So how desperate must we be that we would feel a need to pretend to know for a certainty more than we can demonstrate empirically, or interpret as being "proof" of something or, if so, precisely what?

Are there not members of the "scientific community" who see as a bit forced, the labeling as "evolutionary" of a phenomenon we then proceed to describe in ways that identify instead a continuance of an on-going dual capacity to express certain alternative morphologies... with no change we have as yet isolated as to any DNA/RNA change across a germ pool? In what way does the demonstration that a broad, blunt pattern of alternative expression occurs show current "evolutionary" change, and proof of something other than that, indeed, something is going on of the nature of dual-mode of potential morphological expression that is conserved status quo?

Why cannot we be SPECIFIC about pointing to what evolutionary event we are referring to, to what precise genetic or epigenetic change we are referring?"

Is there a mechanism of selective heritability whereby the gametic cells switch from one mode to the other, without losing the ability to switch back if the environment does so, to the previous population majority mode? Then let us tease it out and expose it for all to see. And let the evidence speak for itself, unless it clearly supports some broad sweeping truth certain.

Surely someone has studied -- or now is contemplating studying -- the INDIVIDUAL DNA of specific individual moths or individual Galapagos finches -- to examine the exact signal paths whereby gametes are "informed" it is time to express the one potential morphology or the other potential morphology, or if not that then what other mechanism or mechanisms account for it. And surely someone has studied, or is contemplating studying, what receptors in the gametes. if that be the case, accept such "intercellular talk" and trigger what "situation appropriate" response follows (instructing offspring, as it were, to express the one mode or the other mode of color patterning or beak length capacity of the species-wide germ pool.

If a gazillion EXAMPLES be found of dark hued moths or lighter-hued moths, or short-beaked offspring or long-beaked ones, then surely there are explanations of what, at the molecular level, is going on. If it is not a continuous condition of conserved on/off switching, then what? If it is not the product of a proactive capacity of sexually reproducing biota to come up with situation-appropriate mutations, then what is it?

Hopefully, you can see that my questions are not based upon any grand narrative of my own, or any other, provenance, nor particularly upon any meta-physical dogma, but rather a solicitation to any in research to look deep down into the decipherment of what specific mechanism or mechanisms are involved in the large-scale phenomena of multiple-morphology-expression-modes capacity. What signals are sent as a result of what stimuli from what cells. What transductions occur along the way. What responses are triggered whereby one morphology or the other becomes expressed? Are not these the kinds of questions science can answer better than the narrative of any grand, sweeping apologetic of how nature works?

When any author (researcher, or merely someone positing himself or herself as a spokesperson for those doing the actual research) speaks about large scale phenomena as being or not being evidence supporting a grand narrative of how things have come to pass... that strikes me as comparable to the story about the man who found a little boy searching the sidewalk under a streetlight. The man asks the boy what he is searching for, and the boy replies, "The quarter I accidentally dropped."

"Where, exactly, did you drop it," the man asks."

"The boy replies, "In the middle of the block."

"Why aren't you searching there, then," the man inquires.

"It's too dark to see down there," responds the boy.

Are we searching under the veritable street light of large, easily observed patterns of
population morphology for answers we are only going to find at the molecular level?

And, of course, I have one other question to go along with that one: "Are we so desperate to appear credible in our ability to do science that some of us insist that the best models we can come up with on circumstantial evidence are the only sensible ones?"

What would be wrong with saying, honestly, "We DON'T KNOW, but based on what information we have so far, here is what we TENTATIVELY SURMISE."

Would it be an insult to science to call it like it is, and not pretend to know more than we know?

Here's to the marvelous findings ahead, and minds open to looking for quarters where they most likely are to be found... and not faking where the line is between what we know, and what we do not know... at least not yet.

Avatar of: James Mallet

James Mallet

Posts: 2

May 15, 2012

KeepItLegal! If I understand your position, you argue that natural selection is correct in this case, but it doesn't satisfy you. However, the gametes of these moths are not "informed" to express black or pale colours, as you suggest. They have physical (genetic) differences, mutations, which enable or disable one alternative; these DNA differences have been shown to exist.

Majerus in this experiment made a very limited point, which was that birds attacked moths with the wrong colour; and in sufficient numbers to explain the changes of frequency of the melanic genes. He felt impelled to do this experiment to counter rumours that the different forms of the moths were not under selection by bird predators.

Avatar of: Guest


May 15, 2012

To James Mallet.

(I drastically edited original response both here and at the web site of SCIENCE (the journal).

To James Mallet.

On DISQUS things get separated from one another by reason of first in time first in place, so let me reproduce your remarks, sentence by sentence here, to assure any reader knows what I am responding to.

You: "KeepItLegal! If I understand your position, you argue that natural selection is correct in this case, but it doesn't satisfy you."

Me: The term "natural selection" means so many different things to so many different people that I am unable to agree or disagree with that statement. That there are causes and effects in nature is intuitive to me, although some highly interesting issues have been raised (as were during the Science Wars) as to how scientifically we can ever hope to distinguish between a cause and effect relationship on the one hand, and a correlative relationship on the other. To illustrate by the most simple of examples, consider the electrical wiring of houses, where a useful component is what electricians call "a two way switch." Each of two two-way switches in an electrical circuit reverses the polarity of the other. One day, one of my children noticed, suddenly, that whereas in all his (aware) experience, the carport light had always come on when the position of the switch by the kitchen door was upward; but this day, he noticed, with great interest (he is kin to me), the light came on when the switch was clicked down, and off when it was clicked up. How could what "caused" the light to come on now "cause" it to go off, he wondered. Again, this is the simplest example I could come up with. There simply is another factor involved, one my son had not been aware of until that moment. I showed him that when the one two-way switch is altered in position, it reverses the polarity of the other, and things went back to what he had perceived to be "NORMAL" when the outside two-way switch was in its other position. This veritable binomial logic circuit illustrates a phenomenon any science literate person would surely be aware of: that the assignment of cause and effect may be almost impossible to establish finitely at the frontiers of the sciences. Not only are far more complex kinds of circuits involved in digital computing's logic circuits, but in the bio-sciences we are stumbling around in the dark on many things. In human physiology, for example, the nature of some cause and effect (or stimulus and response) systems are, so far at least, far and above outside our current capacity to parse. A signal cascade resembles not only an electrical circuit, but varies by way of transduction from one kind of increment to the next, from chemical to electrical to electro-chemical. Normally off gates can function to stop or start things, and normally on gates can start or stop things; so even physically it's a circus. (Forgive me if, in not knowing your background, I tell you what you already know. But, in a nutshell, what biologists and evolutionary biologists DO NOT KNOW FOR A CERTAINTY, too often is glossed over in their apologetics concerning how obvious it is that 'evolution' transpires. Unlike those who work in a field such as ontological research, their credibility is not adversely quantifiable in terms of number of patients who go uncured or unrelieved of symptoms, downstream of applications resting on their claims.
You: However, the gametes of these moths are not "informed" to express black or pale colours, as you suggest.
Me: Perhaps not. I know of no evidence to support it. All I mean to argue is that some such mechanism would HAVE TO EXIST for a species to adapt, in the way much of the literature (not only popular science press but also some peer review writing) implies and in some instances flatly states, that species adapt proactively to changes in their environment -- as though it were a proactive process. (Proactive, I would mean as in a species playing some kind of active role in adapting.) If an evolutionary theorist (or one who mistakenly fancies himself to be such an expert, such as at least one professor I know) believes a species does anything proactive toward mutating in 'needed' or 'opportunistic' ways, then let him cite the mechanism or mechanisms whereby it occurs. To merely cite the 'obvious' fact that it something obviously occurs indeed HAS TO occur, whereby species change in ways that do indeed appear to avail themselves of food utilization, or resistance to predators, or exposure to parasites, pathogens or weather variables is not debatable. What is debatable, by my estimation, is what accounts for it where, at the molecular level, no currently available data confirms that it happens there. Okay, the WHERE does it occur? EITHER there is some means whereby experience (which is almost entirely somatic) directs the show, or signals the germ cells, and they direct the show. If the evolutionary biologists know more than just that 'something' has to account for it and that mysterious 'whatever' magically results in the "EFFECT" we see as "evolution by natural selection," then there has to be a stimulus, a path, and a response at the "mutating" mode that gets it done. Else it does not happen. So what, then? To ask that, is not asinine nor naive. To pretend that the question does not exist, one the other hand, or is not important, is not "science."

Let him who KNOWS what happens at the molecular level (or any other???) tell us the mechanism or mechanism that can be demonstrated. Then let him tell us the cure for all cancers and birth defects and other results that constitute the vast preponderance of all mutations that can be demonstrated in a lab, be accounted for, in a purely random scenario. Then let him who knows that mechanism tell us how "nature" to prevent or cure all cancers, for surely, the many of the same signals, systems, internal cell activities and such are AVOIDED by rapidly radiating species.

You: "They have physical (genetic) differences, mutations, which enable or disable one alternative; these DNA differences have been shown to exist."
Me: Very well then. You say that the lighter colored (spelled coloured in England) moths express their lighter color as a result of having different genes. Let us focus on the word "have" in your sentence. If the lighter hued moths and the darker hued moths "have" gene or a set of genes for lighter color, then why does the article in question assert that it proves something about 'evolution.'
That is my issue.
But let us take a closer look at this issue. Now, take care. For what I am about to say is vitally important here. Brace yourself. If selection occurs AFTER THE RANDOM MUTATION OCCURRED in the case of these moths, then in no way does a species adapt in any sense of the word. It cannot be had both ways. A species cannot blindly change itself to fit a niche, only to be affirmed in its choice of particular mutations required, after the fact. Neither can it, in a single increment of mutational change, avail itself of an opportunity, nor avail itself of a means of escaping an environmental enemy.
As I pointed out regarding mutations they occur in frequency in the following contexts from most to least: 1. Frequently deleterious; 2. Seldom benign but of little immediate significance selectively; 3. Very, very rarely beneficial in some way; and, finally, 4. Astronomically infrequently, beneficial and appropriate to a specific need.
Now if this is IN ERROR, correct me, but articles in both peer review journals and in popular science fluff BOTH tend to indicate that there are scenarios in which some species have rapidly adapted. So how does that occur? Those animals get sequestered on an island and have a golden opportunity to develop cancers and birth defects and lost of strange things like fur on their tongues or a missing heart valve, and also become appropriately adapted because the successes OUTNUMBER THE DELETERIOUS MUTATIONS? Just how obvious can it be that there is something ELSE going on to account for results so often cited as 'explaining' or 'proving' evolution occurs. Of course evolution occurs, if we define it as change in a species over time. My questions are about WHAT occurs that produces a result no molecular data, as yet, supports.
You: Majerus in this experiment made a very limited point, which was that birds attacked moths with the wrong colour; and in sufficient numbers to explain the changes of frequency of the melanic genes.
Me: If that were as far as it goes, I would have nothing to offer but appreciation for research well justified and well-reported. The article and its headline, however, go elsewhere. Do you want me to cite specific examples, or do you see this, yourself?
You: "He felt impelled to do this experiment to counter rumours that the different forms of the moths were not under selection by bird predators."
Me: Very good. And what ELSE does the article do? There's the rub.

Avatar of: Guest


May 17, 2012

All rightee then, by all means, cure my "problem."

Do you mind clarifying for me and other readers which of the following statements you agree with:

a.  The headline of the article, in saying the results of the subject research supports evolutionary theory was totally appropriate, or,

b.  The headline of the article, in saying the results of the subject research supports evolutionary theory was totally inappropriate, because the subject research does not support any assertion of evolutionary theory.

If you agree with a., above, then would you please be so kind as to articulate exactly what assertion or assertions of evolutionary theory the headline of the article references.  And please DO define each term you use in your own unproblematic way, so that I and other readers may know what an unproblematic definition of each looks like.

If you agree with b., above, then no need to explain, as we are on the same page.

Avatar of: texasaggie


Posts: 40

June 9, 2012

 "Is there a mechanism of selective heritability whereby the gametic cells
switch from one mode to the other, without losing the ability to switch back if the environment does so, to the previous population majority mode?"

That is what recessive and dominant alleles are all about.  This has been known since the time of Mendel.  It is the factor that allowed the few melanic peppered moths to exist at the beginning of the industrial revolution and at the end, the few white forms to exist to reproduce once the contamination was cleaned up.

Avatar of: Guest


June 9, 2012

Quite so.  Mendel was quite fortunate to have chosen a model in which dominant and recessive genes expressed an easily observable set of phenotype.  Hopefully I have not left you the impression I am unfamiliar with Mendel's work.

Like you, probably, I have read quite a few papers on the peppered moths.

If you have knowledge of the details of this alternating environmental selection, then you will have no problem telling me which is the dominant phenotype, and which the recessive.  Is the gene for the darker hue the dominant one? 

For purposes of this next question, let us assume so.  In that case, during the period of selection of the darker hued DD and Dd, there would be few dd's; whereas, during the period of selection of the lighter hue, there would be a higher percentage of situational misfits for birds to find.

That would, indeed, be a mechanism whereby there could be at least a preponderance of dark moths, when so selected in the one scenario, and a preponderance of lighter moths, when so selected.

Up to this point it's Bio 101, week one.

Next comes the question of greater importance to me, which is this one:

Why does anyone assert that selection between two EXISTING alleles demonstrates anything about how new mutations occur, which meet the four criteria I listed in a prior comment.

Those four criteria for something to be evolutionary, rather than merely a selecting between EXISTING genotypes (with observable phenotypes), the moths would have come up with something that is:

1.  Genetically original in that species;
2.  Non-deleterious to that species;
3.  Beneficial to that species; and,
4.  Solves a specific issue the species formerly has had in context of the environment at hand.

For nature to select one or the other of two phenotypes, each of which are already there, is not tantamount to an evolutionary event.

At no time have I questioned that evolution of species has occurred.  What I have maintained, however, is that random mutations would not account for an evolutionary "event," which would be an event meeting each of the four criteria above.

A many a paper or textbook has glossed over this, without accounting for the fact that random mutations are overwhelmingly detrimental -- i.e., counter to fitness.  Examples are deformities that hinder, rather than facilitate physical performance, cancers, energy-inefficient processes, anti-homeostatic misappropriate transductions in signal sequences, interferences with healthy immune responses, allergies, over-reactions to certain kinds of stresses or physiological insults...  In short, the odds against a mutation's providing a new and different mutation -- that meets criterion number two , and criterion number three, is astronomically unlikely, on basis of random chance, alone.

And as to criterion number four, picture this:  A species of animal that is well adapted to living in a warm climate suddenly finds its environment getting substantially colder.  A mutation occurs that introduces a new and different allele that beats those astronomical odds of being deleterious, and not only that but, also, is beneficial in that it allows any member inheriting this new trait to have a white spot behind each of its ears... or to have longer toenails... or to grow horns... or to digest ingested bone more efficiently...

Do you see the problem.  Random mutations having met the first three criteria, are not going to benefit this animal as the winters grow longer and colder, unless, in addition to each of the first three criteria it ALSO is solution appropriate to the issue that members of this species are dying off from hypothermia.  What are the odds against THAT?

Many articles gloss over another issue, too.  That issue is this one:  If a species DOES have some capacity to "adapt" to changes in its environment in an "evolutionary" way (meeting each of the four necessary criteria above) then that change is not heritable if it impacts only the somatic cells and processes.  Somehow if any SOLUTION-APPROPRIATE mutation is come up with, then to be heritable it must be passed on gametically.  You do see that, don't you?  That somehow if any heritable proactively adaptive change is to occur rather than on basis of random mutations -- which would be astronomically unlikely to be anything other than deleterious (as in compromising of fitness), then somehow that change must arrive (or, shudder, be somehow "transmitted" from the physiology of the hosts somatic cells to that of the gametes.  Or, at the very least, some how the gametes must either originate and pass on, or somehow be interfered with by some "evolutionary" mechanism to change the way they pass on DNA or RNA, such that the new, non-deleterious, advantageous, immediate-problem-solving SOLUTION is passed along in such a way that not only does the next generation have the new solution but, also, it will pass the phenotype bearing that solution on, in turn, to the next generation after.

Hopefully you can see that the mechanism of dominant and recessive alleles which express a characteristic that may be naturally or artificially selected from an already existing set... comes nowhere near proving ANYTHING that would explain biological evolution.

Again, I take no issue with the fact that evolution DOES occur, and has occurred.

I merely argue -- and on highly solid ground -- that the mechanism of dominant and recessive alleles merely enables selection of alleles that are ALREADY  IN  PLACE.

To suggest that mere selection between two existing alleles already existent in a population, proves how change in a species occurs, or how adaptation to changes in environment occur, or how speciation occurs glosses over many gaps.  Also, to suggest that random mutation enables a species to make changes that are adaptive, glosses over many gaps.

Much progress is going on at the molecular level, and in classical and quantum physics, and the answers to how evolution occurs may be found in years or decades or centuries to come.  But there are no sufficient answers at this time, to how evolution occurs.

Hats off to Mendel and Darwin and others.  But at the frontiers of bio-science there is an enormous amount of information still unknown, and which MUST become known before some of these issues will be explained. 

Despite this reality, there are some in the bio-sciences who either deliberately pretend to know all the answers, or naively presume they know them, because they have not yet thought these issues through.

(Not ALL biologists are vain.  Some of my best friends and relatives hold PhDs in biology, and at least one of them goes about his research with full understanding of how much neither he nor anyone else yet knows.)

(: >)

Avatar of: Guest


June 11, 2012

(Edited by commenter, after initial posting.)

Some rather doctrinaire statements have been made in these comments, about what kinds of issues relating to biological evolution are of no importance to biologists, and what kinds of distinctions between specifics are of no consequence to them. Hopefully those remarks do not speak for most individuals in biology-related research. I know first hand that it does not speak for all, as I am personally acquainted with three individuals who earned PhDs and subsequently left the field -- one who went back to university and became an electrical engineer, at five times the annual income; one who became employed as an organic chemist, and one who now teaches high school chemistry and science, but who does private research at his own expense, and is consulted as a grape taxonomist inside and outside the U. S. Their views have not been represented here.

At any rate, I seem to have left the impression with at least one reader that I was unfamiliar with such things as the writings of Charles Darwin, the contributions of Gregor Mendel and others... much less with more recent research findings relating to phenomena such as transposable element protein domestication, gene fusion and fission, lateral gene transfer, de novo origination... or the very new technology refinements that drastically have reduced labor-time and process costs of sequencing individual cells. Researchers are being enabled to probe farther and farther into things going on at ever smaller scales at inter-cellular and molecular levels. As Lincoln Barnett indicated in his book, "The Universe and Dr. Einstein," (forgive a paraphrase, please): As new concepts emerge, and technology and mathematical models previously deemed a pure logic are found to fit actual findings, those findings become, "... ever more remote from (normal, everyday) human experience. Now the same thing is beginning to occur at the frontiers of biological research, as well.

My issues with some of the assertions of biological evolutionary theory are issues that, if a college freshman were to express them he would be ridiculed, if a grant applicant were to voice them he would be turned down, and for a PhD to express them would be jobacide. The world is not ready, it seems, to be rocked quite yet by any new questions about biological evolution. But at the cutting edge of research, as technology makes further experiential probing possible, some strange unexpected twists and turns are being encountered, some surprises. And, some who dare to do allow themselves to think outside the constraints of what "everybody knows" about evolutionary theory are beginning to whisper, "You ain't heard 'nuthin' yet."

Is this just careless chat? We shall see, shan't we?

With all due respect to the kinds of "giants" (as Issac Newton characterized them) on whose shoulders any and every researcher or great synthesist MUST stand if he would hope to see farther than they, it is my vision, and contention, that biological evolutionary theory has -- for some, but NOT  ALL biology-focused academicians and researchers and apologists -- something of a time-worn narrative which must be defended at all costs, as though the very validity of biological science itself were under attack by any who would question any aspect of it.

Throughout the history of science there have been syntheses that have been slow to become accepted even when acceptance of them was the newer and clearer and more informed, and thus sensible, course of progress, and have died only slowly and painfully when the time has approached for a still newer and more progressive synthesis to upgrade them.  In some instances, literally, bearers of new evidence have lost their heads for refusing to adhere to entrenched stances.  Scientific "wisdom" somehow has advanced not because of entrenched adherence to what "everybody knew" except for a few "fools and radicals," but IN SPITE of it.

As to views about how "evolution" works in the world, the proposition that changes in the morphologies and behaviors and and internal physiologies of species have occurred, is no more than a proposing of the obvious.  Thus the term "evolution" -- insofar as it may be used in reference to the facts of such changes that obviously have occurred, in reference to patterns that can be found (or in some cases arguably have been super-imposed upon those changes), evidence of the dating and timing of those changes... and other such empirically-based, observable and measurable aspects of those changes... is valuable information, as far as it goes.  To say that it "explains" what has occurred, is tantamount to saying, "That which obviously has occurred explains that which obviously has occurred."

No doubt, that sentence will arouse in some readers such a plethora of antagonistic emotional responses that it will prevent, or cloud, what follows.  For the reader who is able to set aside such emotions and read on -- and think on -- here are some daring thoughts about some things that are happening at the frontiers of the sciences today that portend some further "evolution," ahead, if you will, as to how scientists and non-scientists will view the science of biology differently than it has been viewed in the past.  And nothing said here is intended in any way to be insulting or disrespectful toward the "giants" in biology, without whose shoulders to stand on, biologists in the future would have no way of seeing farther than those giants have yet seen.

Just one of the major changes in bio-science (I perceive) arises out of advances that have preceded today's scientific "window on the world" in the scientific fields of classical physics and quantum physics and, in a veritable spiraling leapfrogging way, these sciences and technological advances have alternately enabled one another.  (Mathematics, according to some thinkers, is not a science but merely an art and a tool of science and technology, so, to please those, let the the following statement treat each of three things -- science, mathematics and engineering -- as distinguishable from one another, as three dimensions, as it were, of progress in human learning and applying what humans learn.  Thus, the following:)

Progress in human learning and application of what humanity learns is perpetuated by alternation of science, mathematics and engineering.  That progress could be usefully described as a "spiral."

No more than fifty years ago, many public school textbooks described the "scientific method" as consisting of certain well defined steps that were conceived as applying to any and every scientific endeavor.  Such a definition, however, became increasingly non-applicable, such that today the definition of "scientific methods" has had to be relaxed to include, quite literally, "whatever works" to get the job of learning new and different things about nature done.

Now this next statement may come as a shocker, but here goes: 

A time has come when the emphasis on hypothesis-driven scientific methodologies in the advance of human learning is increasingly sharing the burden of the propagation of that learning with data-driven methodologies.  And the impact of this burden-sharing already has begun to deprive such grand narratives as those of biological Darwinism of much of the impetus they previously provided to inquiry.  It cannot be over-emphasized that the acknowledgement of this reality as to how science is done, and reasoned out, and how it shall be done and reasoned out DIFFERENTLY as mankind moves on into the future, in no way discounts the contribution evolutionary theory has made up to now.
And, indeed, just as there once was a time when it was a blasphemy to say that the world was not flat, or that Earth was not the center of the universe, so too, there will be some "old heads" so entrenched in the Darwin-inspired narrative as to how things have come to be as they are with Earth and mankind, and how they work at ANY AND EVERY LEVEL yet perceived (and unperceived) by the human mind, is giving way to an increasing amount of new data, the understanding of which, and the use of which, is increasingly being driven by new, unexpected, unpredicted discoveries in every field of science. 

Today, rather than finding that species-level emphasis holds the answers to the "most important" of questions facing the science of biology, or that the most significant driver of change in species is "genes," the individual cell, and what goes on inside the individual cell is where many answers will be found to some of our most pressing questions, such as questions about how the human immune system works, how and why cancers occur and how to prevent or cure them, and more.

This is NOT TO SAY that information attained at the intra-cellular level, at the atomic level, and at the sub-atomic level are not required to be carried back, as it were, to be factored into what goes on at the inter-cellular level in whole-body homeostasis in plants and animals generally and in humans.  It is to say that phenomena occurring at one level (the level of, say, the human immune system) will NEVER be parsed exhaustively by the study ONLY of what phenomena occur (emerge) only at that level. 
If anything is forcing itself upon new thinking and new methodology in the sciences today, whether or not we are ready, or willing or able to accept it, and learn from it, it is this:  that human learning and understanding and effective utilization of learning acquired is being discovered to derive in nature from the emergent dynamics of levels of scale ABOVE and BELOW any given scale we would wish to learn about and exploit.

Only if, and to the extent that, evolutionary theory can be adapted to, and seek to account for, BOTH the unique dynamical "rules" or "laws" that apply within a single emergent size-scale, AND the dynamical "rules" or "laws" that apply within an adjacent or nearby unique emergent size-scale, it will not adapt to the situation science is entering upon today, and continue to be useful.

Just as classical physics and quantum physics express two different sets of dynamical "rules" or "laws," so, too, do the human whole-body level of study and the single human cell level behave according to different rules.  In each case, neither dynamic is independent of the other and, in fact, each of two such sets of "rules" and "laws" share certain inter-dynamical connections, or docking points.

Charles Darwin, and those who have stood upon the shoulders of things he discovered and observed, have focused upon the species level, and have (let me compliment them for this) made adjustments, as time has gone on, to add value by availing themselves of new information, new technological tools (enabling observing things going on at ever smaller scales) and new mathematical models; and advances in each of these three dimensions of learning, if you will, have leapfrogged one another forward.

(The designations "macro" and "micro" have become increasing muddy, as technology has enabled us to know things going on at smaller and smaller and smaller scales.)

If, and to the extent, that evolutionary theory were to focus too much upon what goes on at the now-antiquated conception of the "macro" scale, and were to fail to adapt its definitions and theoretical constructs to other scales, it would lose contact with the frontiers.

Now some will read these my words and deny that evolutionary theory is dragging its feet.  Others will say these words make no sense, or that they merely state the obvious, or that they are somehow written for no other purpose than to undermine or impugn the contributions of great thinkers in history.

Others will read these words and see them as no more, and no less, than a solicitation to re-examine thoughts and perceptions which, even if they should be changed, will not be harmed or insulted b y another look.

Follow The Scientist

icon-facebook icon-linkedin icon-twitter icon-vimeo icon-youtube
EMD Millipore
EMD Millipore

Stay Connected with The Scientist

  • icon-facebook The Scientist Magazine
  • icon-facebook The Scientist Careers
  • icon-facebook Neuroscience Research Techniques
  • icon-facebook Genetic Research Techniques
  • icon-facebook Cell Biology Research
  • icon-facebook Microbiology and Immunology
  • icon-facebook Cancer Research and Technology
  • icon-facebook Stem Cell and Regenerative Science
The Scientist
The Scientist