The peppered moth – a video

April 7, 2017 • 8:26 am

by Matthew Cobb

The peppered moth story is one of the best examples of evolution in action. In this brief video, my final year student Tom Parry, tells the whole story, from 19th to 21st centuries. It includes interviews with my colleague Professor Laurence Cook, who carried out some of the recent research confirming how selection acts on the moth, and with Professor Ilik Saccheri of Liverpool University, who has identified the underlying genetic cause of this iconic change due to natural selection. PCC(E) makes a brief photographic appearance, due to the “notoriety” (his term) he attracted in 1998 because of this review.

As with Izzy Taylor’s video earlier this week, Tom needs your feedback – our students have to write a ‘reflective’ piece in which they discuss comments about their videos. So any comments you can make, either below or on YouTube would be gratefully received. If you are a teacher and want to use this with your students, feel free, but please try and collect some feedback from them.


23 thoughts on “The peppered moth – a video

  1. A nice little film that summarizes very well the rise and fall of the two colour forms as well as the rise and fall and rise again of the species as the text book case of evolution in action. My only criticism would be that it would have been nice to have had a little more on the reasons why Kettlewell’s experiments were considered to be inadequately designed and how Majerus addressed these shortcomings in his own experiment. I imagine that you were limited for time, however, so that might have been too much to try and squeeze in. Overall: well done!

    Whilst the Peppered Moth is the best known example of ‘industrial melanism’ in moths it is far from the only one. It would be nice to know whether the mutation involved in these species is the same as the one found in Biston betularia or not.

  2. Jerry Coyne’s concerns about the initial study were not described in any detail. Is that documented somewhere?

          1. Thanks. That makes it clear that in 1998 Jerry was using Majerus’ book as a starting point and conclude that more work was needed.

    1. The Nature citation is the right one, and I stand by the criticisms I made then. If they were off the mark, why did Majerus find it necessary to repeat the experiment “under more natural conditions”?

      Now, after the repeat and other work, I’m quite convinced that the original story based on predation is indeed true.

  3. Very nicely done! Well presented & properly balanced.

    I wonder, what are the chances of such a mutation happening again? Is it present in non-British populations?

    1. Industrial melanism has been recorded in Peppered Moth populations in North America and on the European continent as well as in Great Britain. In these places the changes in the relative frequencies of light and dark forms have followed the same historical pattern in relation to the spread of industrial pollution and the subsequent improvement in air quality.

      Melanic forms occur in a large number of moth species though whether the mutation involved is the same or another one with a similar consequence in the phenotype i don’t know.

  4. Superb.

    Now, if black moths evolved from speckled moths, why are there still speckled moths?

  5. A very well thought-out and researched piece. I think perhaps the most important lesson that can be taken from it is that the path to knowledge in science is not always straight and clean; sometimes it gets a little messy before we get to the end.

  6. TL;DR : both this video and Izzy’s are great!

    My comments might refer to the previous video, since the two videos have a strong experiential or qualitative difference, at least:

    I love the peppered moth story. I am therefore well positioned to hear another take / etc. A number of potentially silly questions came to mind, and I wished sometimes that the pseudo-interviewer would have asked a few questions.

    I also really like this style of video, where we listen to professors who are good at speaking explain things. I like the photography, showing relevant examples of the town, old pictures, etc. there is something so … I don’t know what … seeing the real samples from the – I guess – museum? Watching the hand pick the moth samples up, carefully placing them in a box … I wonder “what are they doing next?” “What is that box for?” The process is very … relaxing? The music helps the mood. Perfect setup for when professor Cook – who is also great to listen to – beings is into the tale – I feel like I’m being taken on a great adventure, like Indiana Jones. (Tech note: like in Raiders of the Lost Ark, the best one).

    If the intention was to introduce viewers to the PM story, I don’t know if they’ll bite because I already know some of the story – but I certainly feel like reading more, asking some more questions. I like to think it will work for someone completely ignorant of the story,.

    Some criticisms of various sorts:

    I think the lighting of prof. Saccheri was too dark. His computer monitor was distracting.Cook was perfectly done, my gaze wandering from his eyes to the moths themselves as I thought about the story.

    It would be nice to show how the soot washes off things, but seeing the final difference is still good.

    I get how this is evolution in action BUT viewers are going to wonder something like “I thought evolution is like dinosaurs-to-birds, monkeys-to-humans, but this is just a color change like in a flower or my siblings ‘ hair color”. Some more should be done to address this idea, … I’ll have to re-listen, but I think merely saying “this is microevolution” just begs the question for the audience- dig a bit more into that, perhaps tying it to the genetics? I don’t know.

    The description of the genetics was very good. I would have liked to know even more about how it works, but that’s for part 2 maybe!

    Perhaps this was deliberate but a video of a bird catching a PM would be good – which birds? Were they in there? I have to listen again….

    Would a set of notes for this be good? I could look down it for such information, as a text companion to the video.

    My last comment for now is in reference to Izzy’s great video : the two videos have a remarkably different experiential “feel” to them : this one puts me in the mood not unlike the seminar hall, sitting back with my tea and cakes, ready to be taken on a grand adventure. Or more Planet Earth style. Izzy is in a category where I think the expectations are … strikingly different- I don’t know why, but it might have to do with feeling like I’m in a lecture hall, or literally reading words from the video with the narrator telling me simultaneously- I like BOTH video styles, but I find myself feeling as if I need to answer for my criticisms of Izzy’s video, as I practically contradict myself here! I think the reason is the expectations, but, I’m going to have to cut this short!…

    1. Many thanks for your thoughtful comments, ThyroidPlanet. I know that Izzy has been very grateful for them, and Tom will be too. We appreciate that it took you some time to write these comments – MC

      1. Thank you Professor Cobb 🙂

        I hope we get to see how the videos turn out after any editing.

        ….(watched again by now)…. “A man called Jerry Coyne”… I got a kick out of that – I bet PCC(E) loves it!?

  7. @Tom. Very well edited – correct sound levels throughout [including the background music which wasn’t intrusive] & visuals that informed the narration.

    However the heart of the story is missing! I’m referring to the points raised in comments 2. [Jonathan] & 3. [rickflick]above. I would have enjoyed a breakdown of how the objections noted by Jerry Coyne were addressed instead of the various ‘talking heads’.

    I loved the b&w pic of Kettlewell at 1:20 apparently tattooed in moths! Very Silence of the Lambs – I realised quickly those were not tattoos, but still a rather striking image.

  8. I enjoyed it — while remembering the old grainy B&W film of Kettlewell at work. Probably the right length and depth for classrooms. And we get to see progress, both in science and the UK atmosphere. Can’t expect much on either front this side of the Atlantic.

    On another note — I’d love to hear [in due time] Jerry’s take on the cephalopod RNA-editing study.

  9. Hi all, as the student responsible for the above film I’d like to say a huge thank you to everyone who has watched and for taking the time to leave feedback – it really is very greatly appreciated! Your comments will be very useful for me and I appreciate they will have taken some time to write, so many thanks!

    Quite a few people have highlighted a lack of detail regarding the criticisms of Kettlewell’s initial experiments – I agree, this is an area I have skated over in the film (as some of you have said, I was limited for time). So just to clarify, there were quite a few problems with those original experiments – a major one being that Kettlewell pinned his moths to tree trunks where they could be seen and eaten by birds, but the evidence for moths actually deciding to settle on trees during the day was very thin and basically anecdotal. This was something Majerus addressed – in his experiments, the moths were set free in a large enclosure, allowing him to record exactly where they settled during the day given the choice. As so happens, he did find that they settled on tree trunks and lateral branches, but this needed to be confirmed because if they didn’t it would completely invalidate Kettlewell’s findings. He also made lots of direct observations of birds coming in and feeding on the moths in the day (and recorded this happening more frequently for black moths than speckled.)
    Another improvement was that because Majerus conducted his experiment over several years, he was able to build up a substantial number of frequency data, meaning he could compare the proportions of the two morphs in the population from year to year. As expected, he found that the ratio of black to speckled shifted in favour of speckled each year, which, alongside his bird predation observations, confirmed bird predation as a selection agent acting against the black morph.
    The reaction from the creationist community to Jerry’s Nature article (and please correct me if I’m wrong Jerry!) ultimately came from an inability to distinguish between the undeniable fact that selection (and so evolution) was happening (as demonstrated by the well documented shift in morph frequencies throughout the 1800s) and the as yet unproven assumption that the agent of that selection was bird predation.

    Hope that clarifies a couple of things, and once again, thank you for the feedback!


    1. I forgot what the line in the video was, but :

      “… Kettlewell pinned his moths to tree trunks where they could be seen and eaten by birds, but the evidence for moths actually deciding to settle on trees during the day was very thin and basically anecdotal.”

      This statement sounds good – why not say this in the video? Add a caveat, trim it down..? I’ll have to re-watch/re-read later, apologies if it’s obvious.

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