Michael Majerus has spent countless hours conducting research on the Peppered Moth (Biston betularia). He’s observed them in the field, bred them in the lab, watched them get eaten by things, kept careful count of the things that he’s seen, and, recently, given a talk about his findings. Jonathan Wells has spent, to the best of my knowledge, absolutely no time doing any actual research on natural selection or moths, but that certainly didn’t stop him from launching a full-throated attack on Majerus.
In this attack, Wells manages to misrepresent a lot of things. This should come as no surprise to those of you who have followed his work in the past, of course. Wells vendetta against all things evolutionary might be a mission from God, but his tactics are hardly heavenly. A Jonathan Wells essay that lies about something is hardly news, and it wouldn’t ordinarily be something that I’d write about. In this case, though, I’m going to make an exception. I simply can’t abide seeing good science and good scientists maligned by a two-bit hack with a defective moral compass.
Wells article is long enough that I’m not going to bother with the whole thing. Instead, I’m just going to hit the more egregious parts. Let’s start with this one:
So crucial evidence for Darwin’s theory – the origin of species by means of natural selection – is missing. And peppered moths don’t provide it.
Even if the classic peppered moth story were 100% true, it would demonstrate only a reversible shift in the proportions of two varieties in a preexisting species. It would tell us nothing about the origin of those varieties, much less of Biston betularia, moths, insects, or animals in the first place. [bold in original]
So the peppered myth is not only dead, but also irrelevant.
To begin with, the peppered moths are, at least in most of the examples I’ve seen, not cited as an example of the formation of a new species. They are cited as an example of how a new trait can spread through a population if it confers a selective advantage.
You see, what Wells does not tell you is that the dark (melanic) form of the peppered moth was entirely unknown prior to 1848. Remember, we’re not talking about an insect from the Amazon here. This is a moth that is found in Great Britain. The Industrial Revolution was well into it’s second half-century, and insect collecting had been a popular hobby for almost as long. Despite these two facts, no dark moth was found prior to 1848. After 1848, the proportion rose rapidly – according to Majerus, over 95% of the moths in some areas were dark forms by the end of the century.
It is true that the frequency of the dark forms is now in decline. The environment is (slowly) recovering from the heavy pollution that favored the dark moths, and as the environment returns to its prior condition the dark form becomes a disadvantage. That does not mean that what happened prior to the environmental recovery is irrelevant to evolution by natural selection – it’s a very good example of the mechanism acting to significantly change the makeup of a population.
Re-enter Michael Majerus. According to an August 25 story in The Independent (London), Majerus has “spent the past seven years collecting data from a series of experiments he has carried out in his own rambling back garden. It has involved him getting up each day before dawn and then spending several hours looking out of his study window armed with a telescope and notepad.”
In his August 23 lecture, Majerus summarized his results as follows:
“I have had occasion to spend time carefully scrutinizing the trunks, branches and twigs of a limited set of trees at the experimental site. During this time I have found 135 peppered moths, resting in what I have no reason to presume are not their freely chosen natural resting sites…
Wells then goes on to criticize this. We’ll get to that set of misrepresentations shortly, but before we do I think it’s important to note that Wells creates the impression here that all that Majerus did was look at resting sites. In reality, that was secondary to the main focus of his experiment.
The bulk of the work that Majerus did involved running a set of predation experiments to see how much more often dark forms were eaten by birds compared with light forms. He compared the results with these experiments with the changes in frequency that he found by doing capture experiments at a different site over a period of several years, and found a strong correlation between the predation likelihood he observed and the actual decline in dark forms.
Put more simply, Majerus found that the decline in the proportion of dark moths is due to natural selection driven by bird predation. Wells definitely doesn’t want to talk about that, so he pretends that it didn’t happen. Instead, he raises some entirely irrelevant criticisms of Majerus’s empirical observations:
Majerus concludes: “While the results may be somewhat biased towards lower parts of the tree, due to sampling technique, I believe that they give the best field evidence that we have to date of where peppered moths spend the day.”
What’s wrong with this picture?
In the seven years during which Majerus was peering out his window, far more than 135 peppered moths visited his back yard, but (as previous research showed) he couldn’t see most of them because they were resting high in the upper branches of his trees. Those he could see from the ground represented only a tiny fraction of the total.
In his 1954 classic, How To Lie With Statistics, Darrell Huff devoted his first chapter to sampling bias. He wrote: “The test of the random sample is this: Does every name or thing in the whole group have an equal chance to be in the sample?” Obviously, the vast majority of peppered moths were NOT in Majerus’s sample because they were resting where he couldn’t see them. Yet the very question he set out to answer was where they rest! If Huff were writing his book today, he might well use Majerus’s statistic as an egregious example of sampling bias.
I’ve got to hand it to Wells. The man calls someone else a liar, lying in the process. That’s chutzpah.
If you haven’t spotted it, the problem with Wells claim is this: Majerus did not claim to have collected a random sample. He did not carry out statistical tests as if he had collected a random sample. He clearly stated that he did not sample randomly, and he described exactly how his sampling method differed from a random sample. The only claim that he made about the resting spot data is that it’s “the best field evidence that we have to date” about where the moths rest. Period. End of claim. Wells’ obfuscatory nattering about random samples is completely irrelevant to that claim.
Finally, we have Well’s (mis)characterization of some remarks Majerus made on the subject of religion at the end of his talk. Wells writes:
And witness Majerus’s mind-numbing conclusion: The “fact of Darwinian evolution” shows that humans invented God and that there will be “no second coming; no helping hand from on high.”
If Jonathan Wells strings multiple very short quotes together in a single sentence, it’s a safe bet that a look at the broader context will show something very different. As it turns out, this is actually one of the times when the safe bet really is a winner. The bit that Wells quoted about the fact of evolution actually appears a few paragraphs after the rest of the material. It also seems that Majerus didn’t actually say that Darwinian evolution disproves God. That fact is merely an inconvenience for Wells, who wasn’t about to let what Majerus said interfere with his description of what Majerus said.
Here’s what Majerus wrote. It’s a long quote, but I’m going to reproduce it in full both to make sure that the full context shows up and because it’s worth reading just for its own sake. I’m also going to conclude with it, because I don’t think I could come up with a better explanation of why it’s so important to keep fighting Wells and the others like him who are trying so hard to extinguish the light of reason.
It is not my place to tell people what to believe. But I know that we are making a horrendous mess of this planet, and I do not have faith in some supernatural intervention putting it right: No second coming; No helping hand from on high; No last minute redemption.
I caught my first butterfly when I was four, and started recording peppered moth forms when I was 10. I am getting old, and have spent my life in scientific enquiry and discovery. And it has been a great life!
Until now, for instead of the vision of a world made better by the appliance of science, I see a future of ever-increasing global problems. I probably won’t see the worst of what’s coming – but I fear for my children, who will face escalating problems of climate change, over-population, pollution, starvation, disease and conflict. And for their children and grandchildren, I have little optimism.
We need to address global problems now, and to do so with any chance of success, we have to base our decisions on scientific facts: and that includes the fact of Darwinian evolution.