Professor Joan Silk, University of California.
Part of the show Animal Communication, Sexual Signalling and Emotions
Chris - Tell us about your experiment because it's fascinating.
Joan - Humans are really quite nice to one another, and we wanted to see whether this was also true for chimpanzees. If you were out shopping today for example, and you had a lot of packages, somebody may have held the door for you. This somebody is probably someone you don't know and will never have the chance to thank or hold the door for in return.
Chris - So it's a selfless act.
Joan - Right. Usually when you ask people why they do these sorts of things, they say that they feel empathy and people seem to express sentiments that they feel concern for how other people are doing.
Chris - So the key question is why we should give a toss about other people.
Joan - Yes and where did it come from? Is it something that we just find in humans or can we also see it in other primates?
Chris - So how did you answer that?
Joan - We did an experiment which was very simple. We gave chimps a choice between one option that would give a reward to themselves and to another chimp that they knew; or an option where food was given just to them.
Chris - You also did this with humans, and as it doesn't cost anything for either the chimp or the human to let the other person or chimp have food, you would expect that they let the other have something too.
Joan - Exactly. But the chimps seem entirely indifferent.
Chris - So they don't really care if their friends are better off or not.
Joan - That's right.
Chris - So that begs the obvious question, where do we get it from?
Joan - That is the obvious question and what we now know is that if this experiment is robust and replicated in other groups, then humans must have got it at some point after the humans and apes split.
Kat - So are chimpanzees very social animals?
Joan - They are indeed. They're very social and co-operate in many different contexts. They hunt together, they share meat, they support each other when they get in trouble, and males at some sites even team up to prevent access to females.
Chris - So it's really strange that they're not intelligent enough to think 'I'll give my mate a reward as well as getting one myself'.
Joan - Well it may be that in the wild, most co-operation is a form of turn-taking. I'll do something nice for you, and you do something nice for me. That's the way it works. Reciprocity may be common in other animals, but what the experiment suggests is that maybe what chimps don't have is a real concern for the welfare of others.
Chris - Do you think that that's the thing that catalysed the evolution of humans. When we did evolve the ability to care about other people, it gave us a big advantage and we had lots of offspring.
Joan - It's certainly true that we are one of the most co - operative species on the planet and that co-operation gets us things like war and charity. I think that the ability to co-operate has made humans incredibly powerful. When you can manage co-operation, it is a very effective mechanism for accomplishing things. Why other animals don't co-operate as much as humans do is a big question because you'd think it would be useful for them as well.
Chris - But isn't it surprising that other animals don't express these tendencies because they clearly give us a big advantage.
Joan - It is surprising, but that's the beauty of science, right? We have a puzzle that we have to explain. Before, we didn't have the puzzle. Now we have to solve it.