emergent properties in biology

David: Can I ask you to define…? Tell me what emergence is and how it’s different from the reductionist programme.

DN: I think that what emerges is functionality. Now that’s a difficult one, I know, but you see, remember, I am a physiologist, so what does a physiologist ask as his main question? It is, ‘What is the function of the heart? What is the function of the liver? What is the function of the leg?’ And you cannot answer that question if you say, ‘It’s just a bunch of molecules interacting.’ You’ve got to address, therefore, the question: what is its purpose?

David: What’s it for?

DN: What’s it for? I can’t avoid that. Now, I know that people who see all of this from a purely molecular point of view will say, ‘But it’s just blind chance that has produced all of this, therefore there is no function.’ But that’s to make the mistake of thinking that because the components don’t have a function individually, that therefore the system doesn’t have a function.

David: So is emergence concentrating on the system level?

DN: Yes.

David: And saying what about the system, though?

DN: Saying that it serves a purpose because that function has emerged. Now, it might have emerged originally from random action. I don’t deny the possibility that life has arisen by purely random chemical reactions initially. I don’t know the answer to that. It’s a question, and it may be right. But once you have got a system that constrains the parts, it takes over.

David: The system takes over?

DN: Yes, the system takes over, because you’ve got… well, in technical terms, you’ve got what the mathematicians would call an attractor: you’ve got something that constrains the components to, as it were, always go to a particular state.

Ard: What you’re saying is if you have an oscillator, like in your heart, and you drill down to the molecular level and you see a protein moving back and forth, and you say, ‘Why is that protein moving back and forth?’, well, there’s no molecular reason for it to move back and forth. The reason is this collective system level that’s channelling information downwards into the cell and not upwards.

DN: Exactly so. And those proteins are proteins that open and close.

Ard: Okay.

DN: And the opening and the closing is controlled by the cell property.

David: So the components build something, but once they’ve built that something…

DN: It takes over.

David: …that something then has an effect on the components that built it from then on?

DN: Exactly so, yes.

Ard: And so if you ignore the fact  that the top-level description is acting on the lower-level…

David: Then you’re missing...

Ard: Then you’re missing the point.

Ard: So you were a physiologist, and you had what people thought were hare-brained ideas about trying to use a computer to calculate the heart, and they didn’t let you in. Is that right?

DN: That’s correct, and for a very interesting reason: they were thinking totally in reductionist terms.

DN: The question put to me was, ‘Where in your equations is the oscillator?’ They couldn’t therefore see that the oscillator was going to emerge from the interactions, and if you separated those components of the model out, they wouldn’t oscillate. So it’s simple. They didn’t understand that.

Ard: So is the story that they let you in only in the morning, or something?

DN: Yes. You remember in those days you had one computer in the whole of London. You had to queue up to use it. So it was running 24 hours a day. I was given between two o’clock and four o’clock, am.

David: That’s slightly unfriendly, isn’t it?

DN: Well I was thought to be the person who was least likely to produce a successful computation. Six months later I got a paper in Nature.

David: But at the time you yourself were a reductionist like everybody else?

DN: Yes, absolutely. That means I couldn’t explain to them what I’ve just said to you. I should have said, ‘It will emerge from the equations.’ Instead, I got a pencil out and scribbled on a bit of paper, in the way that physiologists sometimes do, ‘I think this will interact with that, which will interact with that, and, hopefully, something may come out of this that helps me.’ But I didn’t have the language in those days to say to them, ‘This will be an emergent property.’

So I wasn’t able to reply to these computer experts that the phenomenon of rhythm would emerge from the equations representing the proteins in the cell. If I’d done that, I might have got success more quickly.

David: I think they’d have thrown you out.

DN: Precisely! I think they’d say, ‘What on earth is this about?’ But I wouldn’t even have been able to formulate it like that, and yet it is a downward process of causation in which the properties of the cell constrain those proteins to behave differently from what they would do if they were in a Petri dish.

David: I had imagined that when we talked about levels of emergence, that it was just, sort of, life, and then, maybe, thought. Are those levels of emergence, or are you saying there are lots more?

DN: Yes, I think they are, but I also think that we have to add many more. Just think of any cell in your body. That kind of cell probably took at least a billion years to emerge, because it is unbelievably complicated. It’s made of many different organisms coming together. There’s been a process of what we call symbiogenesis. Your mitochondria in those cells, which are the energy factories, those were originally bacteria.

David: But each of those levels… Do they then bring a whole new set of rules that come with that level?

DN: Yes.

David: Which are rules which weren’t there before?

DN: Exactly so. Because that bacterium is no longer free. It’s no longer free in the sense that it’s now constrained by the system of which it has become part, and, therefore, it’s no longer a bacterium.

David: Right. So is natural selection an emergent rule?

DN: I think that evolution has evolved. I mean, the process of evolution has evolved and there have been many mechanisms at different stages.

David: It makes this link, then, between emergence and the whole discussion about whether you can have genuine novelty in the world, in the universe.

DN: Yes.

David: Or whether the universe came into being with its rules and that’s it. Now we’re just working out the consequences.

DN: Yes.

David: You are saying, if I’ve understood you, because of emergence that, creation is a more open thing?

DN: Precisely, yes.

Ard: And new rules are being created…

DN: …as we go along. Once a system has emerged that constrains the components, it is self-maintaining.

David: Self-maintaining, right. I think you’re saying more than that. It’s self-maintaining but then can generate new emergence?

DN: Exactly so. Yes, yes.

But to people who say, you know, ‘How could all that happen?’, part of my answer would be, first of all, it had a long time in which it could happen. And second, the idea that it happened entirely by blind chance is the wrong way to describe it.

Blind chance might well have been something at the beginning, I don't know. Frankly, I’ve no idea what happened at the very beginning. I don’t think anybody else does either. But once you have the emergence of a property that constrains the rest of the parts, you have the potential for further novelty.

For example, one of those cells can interact with another cell. One can eat the other, or the other way round, or they can come together to combine. Those are new things that couldn’t have happened before the emergence of the cell in the first place. So, yes, each stage creates the potential for new properties.

David: So when you get life emerging out of chemistry, you have something genuinely new and it brings with it its own new rules?

DN: Yes, exactly.

David: So if you knew everything about chemistry, would you be able to predict everything about life?

DN: I think the best way to put that answer is actually to refer to chemistry itself. Let’s take the water molecule. It’s got oxygen; it’s got two hydrogens, and we know the properties of oxygen and the two hydrogens. From that alone you’d find it very difficult to predict the properties of water.

Now, the theoretical chemist will reply to that and say, ‘I know enough about quantum mechanics. I know enough about the movement of electrons around atoms, that I can show how, when you produce the interaction between oxygen and the two hydrogens, I get the properties of water. I could even think in terms of computing that entirely from quantum mechanical descriptions.’

My reply to the theoretical chemist was to say, ‘But you’ve already introduced the interactions in saying that you will compute what happens when those two hydrogens and oxygens come together.’ Because although you’re saying that from your quantum mechanical equations, you can, in principle calculate the behaviour and the emergence of water, what you’re failing to understand is it’s only because you have introduced those constraining factors, which are the relationships of things coming together.

David: But did you realise how big an idea, or as fertile an idea it has been in your life? Because it has been a major… I mean, in some sense it set the course of your life.

DN: It set the course.

David: When did you realise that that was the power of the idea?

DN: I think these kinds of realisations take 20, 30, 40 years, because it upsets everything. Even when I came to write the little book, The Music of Life, nearly ten years ago, I wasn’t there yet, and that process is continuing. But there was still a process to occur which enabled me to start answering questions: where does the meaning come here? Because life is a meaningful process, it has to be. You have to address that question. I don’t think there’s any way of avoiding it.