Ard: Some people of faith would be very nervous that you could explain altruistic behaviour by the laws of nature. What would you say?

MN: That they give a mathematical explanation for why these actions can actually be the ones preferred by natural selection, that’s very good.

Ard: Yeah.

MN: And I’m not nervous, but curiously, long ago, when Newton had the mathematical description of gravity, he asked himself briefly the question, you know, by having a mathematical description of gravity, do I take away from God? Does this take away from God? And he made the remark ‘Hypotheses non fingo’ – I make no hypothesis as to why there is gravity. This could as well be the action of God. So just by having a mathematical description of gravity, it doesn’t take away God as a reason for why there is gravity.

Ard: And the same is true for…

MN: For anything we could learn about the living world: for natural selection, for the mathematical description of natural selection.

David: What was the view of moral behaviour before your work, about whether people could cooperate; whether nature could generate cooperative behaviour?

MN: I think in the realm of evolutionary biology the idea really is that natural selection favours selfishness: that natural selection would promote defectors over co-operators. And, therefore, it is actually difficult to explain the emergence of cooperation. And that was realised as a problem, already, by Darwin: in some sense, he actually said, ‘If you would find a trait in a species that is just there for the benefit of another species, that would invalidate my theory,’ something like that.

David: So he knew it was a problem?

MN: He might have sensed it. Not having had access to the mathematical description of evolution, I would argue that his understanding was partial. But now our understanding is very rigorous, very quantitative.

So natural selection favours defectors over co-operators. That is now the starting point. But now we realise that cooperation is abundant in nature and is kind of needed to explain complex life. So, we have to ask the question, why is it that sometimes natural selection favours cooperation?

David: Yes, because the simple view of natural selection would be…

MN: It won’t.

David: That it can’t.

MN: Yes, and so, then, that is where the mechanisms for the evolution of cooperation come into play, and mechanisms and interaction structure in the population, such that natural selection sees the advantage of cooperation – favours co-operators over defectors.

David: In your work it’s very evident that two are, sort of, locked together. Would you describe that relation like that?

MN: Competition and cooperation are always totally locked together, yes, intertwined. There’s always competition, and there’s sometimes cooperation: competition and cooperation. There’s never the pure form of cooperation, like the utopia. This is never there. Cooperation is never fully stable.

David: And it’s dynamic? It’s constantly switching?

MN: It is dynamic, always changing. Cooperation is never fully stable. Cooperation always gets destroyed, and then you have to worry, ‘How do I rebuild cooperation once it’s destroyed?’

Ard: So, do you think that is also a metaphor for ourselves, our own lives?

MN: Yes, very much so. Theirs is like the cycles, you know, of cooperation and defection, of like friendship and loss of friendship.

Ard: And then it brings me to another question. I’ve heard you speak about the various evolutionary transitions from no life to life, etc. How important do you think the emergence of language was?

MN: So, I consider language the most interesting thing that happened in the last 600 million years.

Ard: Okay.

MN: So 600 million years ago, you know, it was the evolution of complex multi-cellularity on Earth.

Ard: Animals.

MN: Yes, gave rise to animals

Ard: Plants

MN: Plants, the nervous system, the immune system. But ever since then, what was the greatest thing that happened? Arguably human language, because it leads to a new mode of evolution.

Ard: Okay.

MN: So before human language, evolution is almost exclusively limited to genetic evolution. So the information that is being transferred from one generation to the next is coded in genetic structures. But with humans, we have both genetic evolution and cultural evolution: a linguistic evolution, so we can actually have an evolutionary process where one person has an idea and then talks about it and others sort of copy that idea so the idea spreads in the population.

Ard: And why is that such an important… Why do you consider it the most important thing in the last 600 million years?

MN: Because it leads to a new mode of evolution – to a very fast way of evolution. So humans, in a much, much faster time scale, discover, invent all sorts of new things: they don’t have to wait for a new idea to fix that genetic evolution.

Ard: Because new ideas are much more powerful because of language?

MN: Language is a vehicle to transmit, to replicate new ideas in an unlimited fashion.

Ard: And if we now think about cooperation, does language… is that a big step, is that important for cooperation?

MN: Yes, very much. Language is very important for cooperation. Once we go to the mechanism of indirect reciprocity, which I think was a key mechanism for humans, because we have to be able to talk to each other about others.

Ard: So, you think language has hugely changed our ability to cooperate?

MN: Yes, language gives us access to use all five mechanisms, and, in particular, indirect reciprocity, in an unlimited way. So animals without language can still use indirect reciprocity but they have to observe… They have to observe something directly, but humans can talk about things.

David: I just wanted to ask you, when we were sitting here, that you suggested that the cooperative side of natural selection was the side that was responsible for making things, making leaps of… I was going to say leaps forward, but to make things more complex.

MN: Yeah, I believe…

David: Why? Why is that? Why do you think that is?

MN: I think natural selection, competition, gives you better adaptation on a certain level of organisation. But then to move from one level of organisation to a higher level of organisation, so for example from single-cellular organism to multi-cellular organism, cooperation is involved. Even the emergence of human language is somehow based on cooperation, because the two people who want to share some information by communication, they want to do so because they are already in a cooperative relationship.

David: So that cooperative force is more creative in its…

MN: I believe cooperation is the master architect of the complexity of biological life that we see around us.