Darwin in the classroom
How I went about explaining evolution to a class of primary school children.
I’ve just undertaken the daunting task of teaching evolution to a class of 8-11 year old children. This was not the kind of comfortable situation in which you have a room full of students or interested adults who have actively chosen to be there, and would sit and listen in silence for an hour out of politeness if nothing else. Here, I had to keep their attention for the best part of an hour, make it interactive, and I had the huge responsibility of giving them possibly their first introduction to evolution. Fortunately, they were a great bunch of kids, eager both to listen and tell me what they already knew. I also had three teachers in the room for crowd control in case there was a riot brought on by the revelation that goldfish are more closely related to us than they are to sharks.
The class had just started a project on Darwin, so I began with a picture of the man himself, asking them who it was. I chose one of the young Darwin, at the time of the Beagle voyage, and as planned it did throw some of them off scent. I wanted them to know that scientists do a lot of their work when they are young, and that it’s not all about old men with beards. I then gave them the traditional image they were looking for and asked them to tell me what Darwin did and what they knew about evolution. Most of the hands in the room went up, and most of the answers were spot on – Darwin discovered evolution, evolution is animals and plants changing over time, it’s about them being adapted to their environment, it’s about humans being related to monkeys.
I took up the theme of different species being related (and I got them to confirm that they knew what a species is), and said that one of the key points of evolution is that every life form is related to each other. I started by asking if they’d ever done their own family tree, which most them had, and they told me about cousins, and second cousins, and third cousins etc. So I said you can do the same thing with species, and gave them a pictorial tree of life to look at. We then had a few minutes question and answer, where they would tell me a species they wanted to know about, and I would try to find it or a close relative on the tree. Predictably, it was mostly mammals, but we did get a mollusc, a cnidarian and a plant (and they showed up my patchy knowledge of plant taxonomy).
I then said we’d zoom in to look at interesting bits of the tree, and asked them about our own closest relatives. We got there gradually, with the first child saying monkey, the second gorilla, and the third chimpanzee. Then I showed them a great ape phylogeny, with time to last common ancestors on it so we could talk a bit about how long it is since certain pairs of species were the same. They managed to show me up again here, with a woeful inability to talk about Gigantopithecus.
I then asked them what other parts of the tree they’d like to see, confident that someone would say dinosaurs, or at least they would all agree they wanted to see dinosaurs if I had to suggest it to them. So, next up was a simple dinosaur phylogeny, which allowed them to get a bit rowdy shouting out the names of their favourites. We quickly went through the main types of dinosaur, quashed the idea that a pterosaur is a dinosaur, and then moved onto what is the closest living relative of a dinosaur. As luck would have it, one child shouted out crocodiles and the child sitting next to her shouted out birds. That allowed me to say they were both right, explaining that birds are dinosaurs, and crocodiles are their next closest living relative.
It turns out they knew quite a lot about birds evolving from dinosaurs, although quite a lot of them were specifically obsessed with chickens. This was a perfect point to talk about how we know about all these changes deep in the past. After a little bit of searching, they came up with the word fossil, and we talked about what a fossil was. Then I showed them Archaeopteryx, and was very impressed that one of the most enthusiastic children in the class could tell me not only that it was one of the first birds but could tell me its name. I felt a bit mean asking him if he could also spell it, but he did have a valiant attempt, and didn’t seem to complain when I suggested he went and looked it up rather than embarrass myself by getting it wrong in front of them all.
This was a good time to talk about the enormity of evolutionary time, so I got the whole class to hold out their left arm and imagine it was the whole history of the Earth from 4.5 billion years ago. They had a good guess at the origin of life being somewhere on the forearm, but they were pretty amazed to have the age of the dinosaurs being in the middle of their index finger, the Cambrian explosion at the base of that finger, and the entirety of hominid evolution being in the white of their fingernail. For good measure, I got them to stick out their right arm too (while hoping they didn’t all hit each other over the head!) and put the beginning of the universe at the end of that arm.
Now it was time to talk about the how and why of evolution. I started by asking them why animals and plants change over time, and the answer came straight away that they adapt to their environment. Perfect, I said, and showed them Darwin’s finches. After a few digressions on where the Galapagos Islands actually are, and the longevity of giant tortoises, we had adaptation pretty much sorted. So then I asked how they become adapted to their environments. Right on cue, the Archaeopteryx boy gave me a beautiful description of Lamarckism. Given he’d done so well thus far, I didn’t feel bad telling him that was absolutely and precisely… wrong. But I did tell him that was exactly what an important scientist who came just before Darwin thought. I then asked if anyone had heard of natural selection. A couple of hands went up, followed by ‘Yes, I’ve heard of it, but I don’t know what it is’.
And so I asked if they had brothers and sisters, and whether they looked exactly like them. There was some dispute here, but we moved towards them looking quite like them but not exactly. And then I explained that unlike their safe world (you’ve got to give them that safety blanket) the natural world can be tough, and not all offspring survive. And going back to the Lamarckian giraffe example of a few minutes earlier, we established that those who could reach the food slightly better would be more likely to survive and have offspring of their own. At this point I noticed a poster on the classroom wall about Mendel, so we had a few brief words about how genetics makes this possible.
How did Darwin work this out, I asked them? They weren’t sure, so I said he did it in many ways, but one of them was what’s called artificial selection, which is just like natural selection but done by humans and usually faster. I asked how many of them had a pet pigeon, showing them an image of pigeon breeds, which was greeted with much laughter. Oh dear, I said. Fortunately, we can learn the same lesson from dogs, so they all enthusiastically told me about their pets. I think they listened to the explanation at this point, although several of them were out of their seats to get a close look and find their own pet on the dog breeds poster.
Then we returned to natural selection and a classic visual of how it works. Thanks to the work of the late Mike Majerus in rehabilitating the peppered moth story, I felt justified in using it. I got the children to imagine they were a bird predator, and we worked out which moth would be likely to survive on different backgrounds in the photos I showed them. This also allowed a quick sidetrack on the Industrial Revolution and climate change, as well as introducing them to the idea that evolution can be pretty fast sometimes. We returned to this idea in the questions at the end when I explained that illnesses evolve too, and they do it fast, and that’s why we keep getting ill. Evolution occurring right now, and caused by climate change, allowed me to give a little plug for a recent Nature Ecology & Evolution paper on collared flycatchers, although I chose not to get into the complex and potentially awkward subject of sexual selection being involved in that one.
I’d been given the curriculum objectives beforehand (see below – I still think the last one has things slightly the wrong way round), and I felt I’d now covered the ground. So, back we came to a picture of Darwin. I told them he was my favourite scientist, but that I had some other ones who came close. I asked them about theirs, and I got Mendel, because he’s on the curriculum next, but not much else. I therefore quickly flicked through photos of four others who had done something that an 8 year old could grasp. And yes, I had shamelessly made them all women, because I felt they are going to get enough male scientists shown to them over the coming years and a few female role models at this early stage would be a very good balance. So, I gave them Rosalind Franklin (which gave us the chance to say a few things about DNA and link it to Mendel and Darwin), Maria Merian (as they are studying insect metamorphosis), Ada Lovelace (they were all predictably excited to hear about computer programmes) and Linda Buck (olfaction was a pretty easy concept to get across, and I wanted a living scientist and a chance to ask them if they knew what a Nobel Prize is – they didn’t, but they do now).
And that was it. An hour well spent giving the next generation an enthusiasm for science, and hopefully a bit of reasonably accurate knowledge too.
The curriculum for UK year 6:
Sc6/2.3a recognise that living things have changed over time and that fossils provide information about living things that inhabited the Earth millions of years ago
Sc6/3.2b recognise that living things produce offspring of the same kind, but normally offspring vary and are not identical to their parents
Sc6/2.3c identify how animals and plants are adapted to suit their environment in different ways and that adaptation may lead to evolution.