conceptual change - Science-Education-Research

Learning about natural selection and denying evolution

An ironic parallel

Keith S. Taber

I was checking some proofs for something I had written today* [Taber, 2017], and was struck by an ironic parallel between one of the challenges for teaching about the scientific theory of evolution by natural selection and one of the arguments put forward by those who deny the theory. The issue concerns the value of having only part of an integrated system.

The challenge of evolutionary change

One of the arguments that has long been made about the feasibility of evolution is that if it occurs by many small random events, it could not lead to progressive increases in complexity – unless it was guided by some sense of design to drive the many small changes towards some substantive new feature of ability. So, for example, birds have adaptations such as feathers that allow them to fly, even though they are thought to have evolved from creatures that could not fly. The argument goes that for a land animal to evolve into a bird there need to be a great many coordinated changes. Feathers would not appear due to a single mutation, but rather must be the result of a long series of small changes. Moreover, simply growing features would not allow an animal to fly without other coordinated changes such as evolving very light bones and changes in anatomy to support the musculature needed to power the wings.

The same argument can be made about something like the mammalian eye, which can hardly be one random mutation away from an eyeless creature. The eye requires retinal cells, linked to the optic nerve, a lens, the iris, and so on. The eye is an impressive piece of equipment which is as likely to be the result of a handful of random events, as would be – say, a pocket watch found walking on the heath (to use a famous example). A person finding a watch would not assume its mechanism was the result of a chance accumulation of parts that had somehow fallen together. Rather, the precise mechanism surely implies a designer who planned the constructions of the overall object. In 'Intelligent Design' similar arguments are made at the biochemical level, about the complex systems of proteins which only function after they have independently come into existence and become coordinated into a 'machine' such as a flagellum.

The challenge of conceptual change

The parallel concerns the nature of conceptual changes between different conceptual frameworks. Paul Thagard (e.g., 1992) has looked at historical cases and argued that such shifts depend upon judgements of 'explanatory coherence'. For example, the phlogiston theory explained a good many phenomena in chemistry, but also had well-recognised problems.

The very different conceptual framework developed by Lavoisier [the Lavoisiers? **] (before he was introduced to Madame Guillotine) saw combustion as a chemical reaction with oxygen (rather than a release of phlogiston), and with the merits of hindsight clearly makes sense of chemistry much more systematically and thoroughly. It seems hard now to understand why all other contemporary chemists did not readily switch their conceptual frameworks immediately. Thagard's argument was that those who were very familiar with phlogiston theory and had spent many years working with it genuinely found it had more explanatory coherence than the new unfamiliar oxygen theory that they had had less opportunity to work with across a wide range of examples. So chemists who history suggests were reactionary in rejecting the progressive new theory were actually acting perfectly rationally in terms of their own understanding at the time. ***

Evolution is counter-intuitive

Evolution is not an obvious idea. Our experience of the world is of very distinct types of creatures that seldom offer intermediate uncertain individuals. (That may not be true for expert naturalists, but is the common experience.) Types give rise to more of their own: young children know that pups come from dogs and grow to be adult dogs that will have pups, and not kittens, of their own. The fossil record may offer clues, but the extant biological world that children grow up in only offers a single static frame from the on-going movie of evolving life-forms. [That is, everyday 'lifeworld' knowledge can act as substantial learning impediment – we think we already know how things are.]

Natural selection is an exceptionally powerful and insightful theory – but it is not easy to grasp. Those who have become so familiar with it may forget that – but even Darwin took many years to be convinced about his theory.

Understanding natural selection means coordinating a range of different ideas about inheritance, and fitness, and random mutations, and environmental change, and geographical separation of populations, and so forth. Put it all together and the conceptual system seems elegant – perhaps even simple, and perhaps with the advantage of hindsight even obvious. It is said that when Huxley read the Origin of Species his response was "How extremely stupid not to have thought of that!" That perhaps owes as much to the pedagogic and rhetorical qualities of Darwin's writing in his "one long argument". However, Huxley had not thought of it. Alfred Russel Wallace had independently arrived at much the same scheme and it may be no coincidence that Darwin and Wallace had both spent years immersing themselves in the natural history of several continents.

Evolution is counter-intuitive, and only makes sense once we can construct a coherent theoretical structure that coordinates a range of different components. Natural selection is something like a shed that will act as a perfectly stable building once we have put it together, but which it is very difficult to hold in place whilst still under construction. Good scaffolding may be needed.

Incremental change

The response to those arguments about design in evolution is that the many generations between the land animal and the bird, or the blind animal and the mammal, get benefits from the individual mutations that will collectively, ultimately lead to the wing or mammalian eye. So a simple eye is better than no eye, and even a simple light sensitive spot may give its owner some advantage. Wings that are good enough to glide are useful even if their owners cannot actually fly. Nature is not too proud to make use of available materials that may have previously had different functions (whether at the level of proteins or anatomical structures). So perhaps features started out as useful insulation, before they were made use of for a new function. From the human scale it is hard not to see purpose – but the movie of life has an enormous number of frames and, like some art house movies, the observer might have to watch for some time to see any substantive changes.

A pedagogical suggestion – incremental teaching?

So there is the irony. Scientists counter the arguments about design by showing how parts of (what will later be recognised as) an adaptation actually function as smaller or different advantageous adaptations in their own right. Learning about natural selection presents a situation where the theory is only likely to offer greater explanatory coherence than a student's intuitive ideas about the absolute nature of species after the edifice has been fully constructed and regularly applied to a range of examples.

Perhaps we might take the parallel further. It might be worth exploring if we can scaffold learning about natural selection by finding ways to show students that each component of the theory offers some individual conceptual advantages in thinking about aspects of the natural world. That might be an idea worth exploring.

(Note. 'Representing evolution in science education: The challenge of teaching about natural selection' is published in B. Akpan (Ed.), Science Education: A Global Perspective. The International Edition is due to be published by Springer at the end of June 2016.)

Notes:

* First published 30th April 2016 at http://people.ds.cam.ac.uk/kst24/

** "as Madame Lavoisier, Marie-Anne Pierrette Paulze, was his coworker as well as his wife, and it is not clear how much credit she deserves for 'his' ideas" (Taber, 2019: 90). Due to the times in which they works it was for a long time generally assumed that Mme Lavoisier 'assisted' Antoine Lavoisier in his work, but that he was 'the' scientist. The extent of her role and contribution was very likely under-estimated and there has been some of a re-evaluation. It is known that Paulze contributed original diagrams of scientific apparatus, translated original scientific works, and after Antoine was executed by the French State she did much to ensure his work would be disseminated. It will likely never be know how much she contributed to the conceptualisation of Lavoisier's theories.

*** It has also been argued (in the work of Hasok Chang, for example) both that when the chemical revolution is considered, little weight is usually given to the less successful aspects of Lavoisier's theory, and that phlogiston theory had much greater merits and coherence than is usually now suggested.

Sources cited:

Taber, K. S. (2017). Representing evolution in science education: The challenge of teaching about natural selection. In B. Akpan (Ed.), Science Education: A Global Perspective (pp. 71-96). Switzerland: Springer International Publishing
Taber, K. S. (2019). The Nature of the Chemical Concept: Constructing chemical knowledge in teaching and learning. Cambridge: Royal Society of Chemistry.
Thagard, P. (1992). Conceptual Revolutions. Oxford: Princeton University Press.

The moon is a long way off and it is impossible to get there

Does our whole system of physics forbid us from believing someone has been on the moon?

Keith S. Taber

Image by WikiImages from Pixabay (with Emoji superimposed)

I never had the chance to interview Ludwig for my research, but was intrigued when I found out about his outright dismissal of the possibility of manned missions to the moon.

There are of course people who are strongly committed to ideas at odds with current scientific consensus – suggesting the earth is flat; that evolution does not occur; that COVID-19 was deliberately produced in a laboratory; that governments have physical evidence of alien visitors, but deny it and keep all relevant documentation classified; and so forth.

Moon landing deniers

Even in the United States of America, the home of the Apollo missions, surveys regularly show that a substantial minority of people doubt that people ever actually went to the moon, and think the Apollo moon landings were faked. Why would NASA have gone to such trouble with the collusion of the US Government machinery and the support of Hollywood studios?

As President Kennedy had put such weight on (American) people getting to the moon before the end of the 1960s, then – the argument goes – once it became clear this was technically impossible, it became important to convince the population that JFK's challenge had been met by a massive initiative to forge and disseminate evidence. There has been something of an industry in explaining how the photographs released by NASA can be seen to have been clearly faked if one looks carefully enough and knows a little science.

Unreasonable doubt?

I try to be someone who is always somewhat sceptical (as any scientist should be) of any claims, no matter how widely believed, as in time some canonical ideas are found to be flawed – even in science. But I tend to give little credence to such conspiracy theories.

Sometimes there are good reasons why science is doubted by sections of the public when it seems to conflict with well established world-view beliefs deriving from religious traditions or traditional ecological knowledge which has sustained a culture for a great many generations. So, even when the science is well supported, we can sometimes understand why some people find it difficult to accept. But the Apollo missions being faked in a film studio: surely that is just the kind of nonsense that only ignorant cranks like to believe – isn't it?

Ludwig on the sure belief that no one has been to the moon

Thus my interest in Ludwig, who was certainly not an ignorant person. Indeed he was highly intelligent, and something of an intellectual – a deep thinker who was very interested in the nature of knowledge and considered issues of how we could ground our beliefs, given that the evidence was never sufficient to be absolutely sure.

He thought that individual ideas were convincing when they were embedded in a 'nest' of related ideas – what we might call a conceptual framework. One example he discussed was his accepting that people always had parents: he thought this "sure belief" was based "not only on the fact that I have known the parents of certain people but on everything that I have learnt about the sexual life of human beings and their anatomy and physiology: also on what I have heard and seen of animals". Ludwig thought that although this could not be considered definite proof, it was robust grounds for someone to accept the belief.

Another example of such a sure belief was that a person could be confident that they had never been on the moon,

A principal ground for [a person] to assume that he was never on the moon is that no one ever was on the moon or could come [i.e., get] there; and this we believe on grounds of what we learn.
¶171

Physics forbids moon landings

Ludwig seemed to consider the impossibility of people getting to be on the moon was something he could be pretty sure of,

"But is there no objective truth? Isn't it true, or false, that someone has been on the moon?" If we are thinking within our system, then it is certain that no one has ever been on the moon. Not merely is nothing of the sort ever seriously reported to us by reasonable people, but our whole system of physics forbids us to believe it. For this demands answers to the questions "How did he overcome the force of gravity?" "How could he live without an atmosphere?" and a thousand others which could not be answered…

The intellectual status of unreasonable people

So someone making such a claim would not be a 'reasonable' person in Ludwig's evaluation. So how would Ludwig feel about such an unreasonable person?

We should feel ourselves intellectually very distant from someone who said this.
¶108

But of course there are people who claim this has indeed happened, that we have been to the moon,and walked there and whilst there collected rocks and indeed played golf. (Had this been more recent, we would perhaps instead have danced the tango and baked cakes.) NASA astronauts have since often acted as ambassadors for space science, and told their stories across the world, including to the young – enthusing many of them about space and science.

How might Ludwig respond to a child who had met one of those Apollo astronauts who claimed to have walked on the moon?

Suppose some adult had told a child that he had been on the moon. The child tells me the story, and I say it was only a joke, the man hadn't been on the moon, no one has ever been on the moon, the moon is a long way off and it is impossible to climb up there or fly there.

Ludwig adds, rhetorically,

If now the child insists, saying perhaps there is a way of getting there which I don't know, etc. what reply could I make to him?
¶106

Believers in moon landings are ignorant and wrong

So how could Ludwig explain that there are many people, indeed a majority today, who do believe that people have visited the moon, and returned to earth to tell others about the experience?

What we believe depends on what we learn. We all believe that it isn't possible to get to the moon; but there might be people who believe that that is possible and that it sometimes happens. We say: these people do not know a lot that we know. And, let them be never so sure of their belief-they are wrong and we know it.
If we compare our system of knowledge with theirs then theirs is evidently the poorer one by far.
¶286

So, just as I might suspect the moonshot deniers are somewhat ignorant, for Ludwig it is the reverse: it is those who think people can get to the moon who have poor knowledge systems and are simply wrong.

Now I suggested above that Ludwig was an intelligent and reflective person – indeed he worked as a school teacher, both in primary and secondary education – so his views may seem incongruent. As some readers may have suspected, I am being a little unfair to Ludwig. I pointed out at the outset that I never had the chance to interview Ludwig – indeed I never met him, although he did spend part of his life in Cambridge where I now work.

We can all be wrong

Ludwig did not live to see the moon landings, as he died in 1951 almost a decade before I was born (of parents – he was right about that), shortly after he wrote the material that I have quoted above. That is a few years before Sputnik was launched by the Soviet Union and the 'space race' began. So, Ludwig was not a denier of the moon landings as such, refusing to accept the media accounts, but rather a denier of the possibility of there ever being moon landings at a time when no one was yet actively planning the feat.

Ludwig was wrong. But had he lived another 20 years I am pretty sure he would have changed his mind. That's because one of the things he was best known for was changing his mind.

Having written a highly influential book of philosophy that convinced many intellectuals he was one of the greatest thinkers of his time, if not all time (the Tractatus Logico-Philosophicus) he took a long sabbatical from Academia, only to later write an equally influential and profound book (that he did not live to see published – the Philosophical Investigations) that contradicted his earlier ideas. Had Ludwig seen the technological developments of the 'space race' in the 1960s, it seems certain – well, a sure belief – that he would have accepted the possibility of people going to the moon.

However, when I first read the comments I quote above I was struck by how such a highly intelligent and deep thinker could be so sure that getting people to the moon was not possible that he actually chose to use the idea of people on the moon as an exemplar of something that was impossible ("it is certain that no one has ever been on the moon"), and indeed contrary to the laws of physics.

Presumably at the time he was writing he could assume most intelligent people would fully accept his position (as "we all believe that it isn't possible to get to the moon") and see the suggestion of people going to the moon as absurd enough to stand as an example of an idea that could not be accepted by us reasonable people, only by someone "intellectually very distant" from us.

However, barely a decade later JFK was convinced enough of the possibility of getting people safely to the moon and back to commit his nation to achieving it – and a decade after that men being on the moon was already ceasing to be seen as anything out of the ordinary (until the near disaster of the Apollo 13 mission got the flights back into the popular imagination).

I do not present this example to ridicule Ludwig Wittgenstein. Far from it. But it does make me reflect on those things that we think we can treat as 'sure beliefs'. Even the most intelligent and reflective of us can be very wrong about things we may treat as certain knowledge. That's always worth keeping in mind.

Nothing is absolutely certain, except, perhaps, uncertainty itself!

All citations are from ¶ in Wittgenstein, L. (1975). On Certainty (D. Paul & G. E. M. Anscombe, Trans. G. E. M. Anscombe & G. H. v. Wright Eds. Corrected 1st ed.). Malden, Massachusetts: Blackwell Publishing.

Particles in ice and water have different characteristics

Making a link between particle identity and change of state

Keith S. Taber

Bill was a participant in the Understanding Science Project. Interviews allow learners to talk about their understanding of science topics, and so to some extent allow the researcher to gauge how well integrated or fragmented a learner's ideas are.

Occasionally there is a sense of 'seeing the cogs turn', where it appears that the interview is not just an opportunity for reporting knowledge, but a genuine site for knowledge construction (on behalf of the students, as well as the researcher) as the learner's ideas seem to change and develop in the interview itself.

One example of this occurred when Bill, a Y7 student, explained what he had learnt about particles in solids, liquids and gases. Bill seemed unsure if the particles in different states of matter were different, or just had different properties. However, when asked about a change of state Bill related heating to changes in the way particles were arranged, and seemed to realise this implied the particles themselves were the same when a substance changes state. Bill seemed to be making a link between particle identity and change of state through the process of answering the researcher's questions.

Bill introduced the idea of particles when talking about what he had learn about the states of matter

Well there's three groups, solids, liquids and gases.
So how do you know if something is a solid, a liquid or a gas?
Well, solids they stay same shape and their particles only move a tiny bit.

This point was followed up later in the interview.

So, you said that solids contain particles,
Yeah.
They don't move very much?
No.
And you've told me that ice is a solid?
Yeah.
So if I put those two things together, that tells me that ice should contain particles?
Yeah.
Yeah, and you said that liquids contain particles? Did you say they move, what did you say about the particles in liquids?
Er, they're quite, they're further apart, than the ones in erm solids, so they erm, they try and take the shape, they move away, but the volume of the water doesn't change. It just moves.
Okay. So the particles in the liquid, they seem to be doing something a bit different to particles in a solid?
Yeah.
What about the particles in the gas?
The gas, they, they're really, they're far apart and they try and expand.
Does that include steam, because you said steam was a gas?
Yeah.
Yeah?
I think.
So, we've got particles in ice?
Yeah.
And they have certain characteristics?
Yeah.
And there are particles in water?
Yeah.
That have different characteristics?
Yeah.
And particles in gas, which have different characteristics again?
Yeah.
Okay. So, are they different particles, then?
N-, I'm not sure.

There are several interesting points here. Bill reports that the particles in liquids are "further apart, than the ones in … solids". This is generally true when comparing the same substance, but not always – so ice floats in water for example. Bill uses anthropomorphic language, reporting that particles try to do things.

Of particular interest here, is that at this point in the interview Bill did not seem to have a clear idea about whether particles kept their identify across changes of state. However, the next interview question seemed to trigger a response which clarified this issue for him:

So have the solid particles, sort of gone away, when we make the liquid, and we've got liquid particles instead?
No {said firmly}, when a solid goes to a liquid, the heat gives the particles energy to spread about, and then when its a liquid, it's got even more energy to spread out into a gas.
So we're talking about the same particles, but behaving differently, in a solid to a liquid to a gas?
Yeah.
That's very clear.

It appears Bill had learnt a model of what happened to the particles when a solid melted, but had not previously appreciated the consequences of this idea for the identity of particles across the different states of matter. Being cued to bring to mind his model of the effect of heating on the particles during melting seemed to make it obvious to him that there were not different particles in the different states (for the same substance), where he had seemed quite uncertain about this a few moments earlier.

Whilst this has to remain something of a speculation, the series of questions used in research interviews can be quite similar in nature to the sequences of questions used in the method of instruction known as Socratic dialogue – a method that Plato reported being used by Socrates to lead someone towards an insight.

So, a 'eureka' moment, perhaps?

Liquid iron stays a liquid when heated

Keith S. Taber

Sophia was a participant in the Understanding Science Project. In Y7, Sophia had told me that if molten iron was heated "some of it would evaporate but not all of it, 'cause it's not like water and it's more heavy". She thought only "a little" of the iron would evaporate to give iron vapour: The rest "really just stays as a liquid". [See 'Iron is too heavy to completely evaporate'.]

Just over a year later (in Y8) Sophia had been studying "that different erm substances have different freezing and melting and boiling points, and some aren't like a liquid at room temperatures, some are a solid and some are a gas and things like that".

Give me an example of something else that's a solid at room temperature?
Iron.
Do you think iron would have a melting point?
Yeah.
Yeah, and if I, what would I get if I, if I heated iron to its melting point?
It would become a liquid.
And why would it do that?
Because it's got so hot that particles – they have spread out or something?
So what do you think would happen if I heated the iron liquid?
It would stay a liquid.
No matter how much I heated it?
It might, I don't know if it would become a vapour.
Can you get iron vapour?
No, I don't think so.
You don't think so?
No.

So it seems that Sophia had shifted from accepting that iron would partially evaporate (when learning about the particle model of the different states), to considering that iron (probably) can not become a vapour. The notion of iron as a gas is not something we can readily imagine, and apparently did not seem very feasible. In part this might be because we think of iron the material (a metal, which cannot exist in in the vapour phase) rather than as a substance that can take different material forms.

It seems Sophia's prior knowledge of iron the material was working against her learning about iron the substance, an examples of a grounded learning impediment where prior knowledge impedes new learning.

In Y7 Sophia had seemed to have a hybrid conception where having been taught a general model of the states of matter and changes of state, she accepted the counter-intuitive idea that iron could evaporate, but thought that (unlike in the case of water) it could not completely evaporate . This might have been a 'stepping stone' between not accepting iron could be in the gaseous state and fitting it within the general model that all substances will when progressively heated first melt and then evaporate (or boil) as long as they did not decompose first.

However, it seems that a year later Sophia was actually more resistant to the idea that iron could exist as vapour and so now she thought molten iron would remain liquid no matter how much it was heated. If anything, she had reverted to a more intuitive understanding. This is not that strange: it has been shown that apparent conceptual gains which are counter to strongly held intuitions that are brought about by teaching episodes that are not regularly reinforced can drop away as the time since teaching increases. Conceptual change does not always involve shifts towards the scientific accounts.

[Sophia was in lower secondary school when I talked to her about this: but I was also told by a much older student that the idea of iron turning into a gas sounds weird.]