Ard: Could you say that something like our empathy instinct, if you want to call it that, is like a moral compass pointing us in that direction?

FdW: Yes, if that's how you want to phrase it, yes. We have a built-in sense of fairness which relates to our cooperative tendencies. We have a sense of reciprocity which is very important in a chimpanzee society: doing each other favours and obligations and so on. We have a sense of empathy, and we're in tune with the situation and the feelings of others. And, yes, all those natural tendencies that we have, they steer us in a particular direction in our social relationships, especially social relationships with the in-group.

Now with the out-group the story is sometimes quite different, and that's why we have a lot of trouble applying our moral principles outside of our group. And at the moment, of course, in the world we're trying to do that. We talk about universal human rights, which is sort of stretching… We're trying to stretch the system basically.

Ard: So, thinking about the parable of the Good Samaritan, in some sense that's a story about care for someone who's in the out-group. Is that pushing us beyond our moral compass?

FdW: Yes, I think that is typically human, and that's where the top-down processes come in. So I think we have a lot of bottom-up morality, which basically comes from our primate social tendencies and… and that's a view that Darwin also had.  But then what we humans do – and I don't think my chimpanzees do that in any way – is we try to translate that in to justifications and in principles, and we come up with a narrative – and actually the Good Samaritan is a narrative – we come up with a narrative that justifies our behaviour. And then we are capable of applying those principles outside the usual box, which is the in-group where it really evolved. I think morality evolved for the in-group, not for the out-group. We could hack off their heads, it was fine.

But then with our mental capacities, we say, ‘Well, why is that fine? Maybe it's not fine. Let's question it.’ And, for example, the Geneva Convention, which tells us how to treat our enemies, is such an innovation, and I don't think chimpanzees would ever come up with a Geneva Convention. ‘The enemies?’ ‘Get rid of them. That's the main thing. Enemies are not there to be treated well.’

So, that's a human thing, I think, and that's a top-down process where we then use these justifications and narratives that we have and say can we apply them outside of the group, yes or no? It's a sort of intellectual experiment. And, of course, if the in-group was not doing well – let's say we're all starving and we have terrible circumstances – we might care less about the out-group. And so it is dependent on the circumstances. But nowadays we live in societies which are wealthy enough that we can start thinking about these issues.

Ard: So in some sense these are things that transcend our kind of moral instincts…

FdW: They're built on them, because we still use that bottom-up morality to arrive at the principles and justifications, but then we take it one step further, which is an intellectual step, really it's more like a cognitive step, and that's maybe why I don't see any of that in my primates.