ROBERT SIEGEL, HOST:
A new paper in the journal Nature describes a grisly massacre that happened about 10,000 years ago in Kenya. It's the earliest known evidence of human warfare. The site was uncovered in 2012, and Cambridge University professor Robert Foley is among the scientists who have been studying the discovery. Welcome to the program.
ROBERT FOLEY: Thank you very much.
SIEGEL: The site is in northern Kenya. What exactly did your team uncover?
FOLEY: What we found is an area that's about a hundred meters by 20 or 30 meters. And in that area, we found 27 skeletons or partial skeletons or fragments of skeletons. And what we saw at first was just the back of somebody's skull just peeping through the ground. And Marta Lahr, who's the director of the project - she exposed the skeleton, and then it became clear that there were other skeletons around. Some of these had clear signs of having died violently.
SIEGEL: Was there any sign of the implements with which they might have met their demise?
FOLEY: Yes. So the traumas we were able to see basically fall into three categories. So one is what you'd think of as a blunt instrument. Were talking, here, probably wooden - big wooden, heavy clubs. And these have been used to completely smash the skulls. Then we have some where the clubs may have actually had inserted in them small, little stone blades to make them really more unpleasant. And then the third type were little stone blades or tips - probably arrowheads, which were projectiles. And these were actually embedded into one of the skulls so that clearly, we can say, well, they were both clubbed to death and probably shot with projectiles.
SIEGEL: And were these, by the way, all males skeletons, or could you tell?
FOLEY: No, no. It's men and women and children.
SIEGEL: And what are the theories behind what might've produced this result?
FOLEY: Our interpretation that this was the product of some sort of intergroup conflict, you know? Whether you want to call it warfare or not, it is a matter of definition. But it's lethal conflict between two groups.
Now, the reason we say that is that the skeletons we found were not buried. I mean, they're not in graves. They haven't been interred. They're lying where they died, and that's an extraordinarily unusual - I mean, it's unusable the find something like that. So we're interpreting this as being one group ambushing, attacking, taking by surprise in conflict with another one.
SIEGEL: And how does this find altar our understanding of life 10,000 years ago in Northern Kenya?
FOLEY: Well, the really critical thing is that the people involved were hunter-gatherers, and I think many people in anthropology and archaeology would say that warfare is something that really starts seriously once people have settled down, once they're in permanent settlements, they start to have livestock, they start to have crops. And those are things that need to be defended or they're things that you can steal. What we see here is a hunter-gatherer group also engaging in warfare. So it tells us that the conditions under which human societies will fight each other are broader, are more diverse than previously thought.
SIEGEL: Do you come away from this study - or I guess you're still in the midst of it. But do you find yourself thinking that perhaps we humans are more innately aggressive than you might've thought before?
FOLEY: Well, I think the key thing is that we have evidence for it, you know? Thinkers, philosophers, scientists speculated on this forever. So it's always been out there as a possibility. Do I think that we're less pleasant than I did - probably not. I mean, I don't think we're specifically violent and aggressive, and nor are we specifically peaceful and all-loving at all. I mean, I think the key thing about human nature is that we have the capacity for both. And our survival depends enormously on being able to cooperate. I mean, that's what makes groups exist. But under certain conditions, we are also very violent and can be aggressive and murderous in our activities. So I think it's wrong to characterize humans as either warlike or peaceful. We're both.
SIEGEL: Professor Foley, thank you very much for talking with us today.
FOLEY: It's a pleasure.
SIEGEL: That's Cambridge University professor Robert Foley on the discovery of the site of the remains of an ancient conflict in Kenya. It's the earliest-known evidence of human warfare.