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A chimp
BBC Two, Thursday 8 January 2004, 9pm
The Demonic Ape
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Demonic Ape - transcript

NARRATOR (DILLY BARLOW): It’s one of the great stories of modern science. A young woman befriended a group of wild chimpanzees in the African rainforest. Because of her discoveries, everything we thought we knew about chimpanzees and ourselves was turned upside down.

Dr JANE GOODALL: If you look in to the eyes of a chimpanzee you know you're looking in to the eyes of a thinking feeling being.

Prof SARAH BOYSEN (Columbus State University): When you watch chimpanzees playing, adults with humans or chimpanzee children, infants playing with one another, there’s a real joyfulness and love of life that you can see.

NARRATOR: This is the story of our closest living ancestors and what we thought they would teach us about ourselves. But it is also the story of a tragedy that occurred in the heart of Tanzania. A tragedy that has called in to question so much of what we appeared to have learnt about chimpanzees and us.

NARRATOR: On May 15th 2002 Rukia Sadiki set off to meet her husband. She was with her niece and her baby daughter Miasa. It was a route they had taken many times before from their village, through Gombe National Park to Lake Tangakika. What they didn’t know is that on that day they were being followed. The attacker snatched the child and dragged her in to the jungle. Miasa’s body was found in a tree. She had been partially eaten. Rukia Sadiki had known the killer all his life. Today he is still at large and capable of striking again. His name is Frodo and he is the most famous chimpanzee on the planet. He is twenty seven years old and throughout his life he’s been studied by scientists and filmed by TV crews. This tragedy shocked the world. The press said Frodo should be put down, but others claimed it was just natural behaviour.

Dr JANE GOODALL: Frodo killed a human infant, something which we’d been predicting would happen for a very, very long time. Because chimpanzees are hunters and although at Gombe their favourite prey is monkey infants, human beings are just one other kind of primate.

NARRATOR: But this was more than just a human tragedy. It has raised fundamental questions about chimpanzee research and what these animals have taught us about the origins of human behaviour. The saga of Frodo began even before he was born. It all started back in 1960 with a young twenty seven year old woman.

Dr JANE GOODALL: When I left school at eighteen my friends almost all of them went to university, we couldn’t afford it, so it was my mother and she said well why don't you do a secretarial course and then you can get a job anywhere in the world.

NARRATOR: Jane Goodall became secretary to the famous palaeontologist Louis Leakey. Precisely because she had no preconceptions about these animals Leakey asked her to study the chimpanzees of Gombe by the shores of Lake Tanganyika in Tanzania.

Dr JANE GOODALL: I remember the first day I arrived at Gombe, going along the shore of the lake in the little boat. And I looked up at the hillside with the thick valleys of forest in-between and I remember thinking how will I find the chimps. I felt so tiny, a young girl out on her own in the forest. The chimpanzees ran away from me for weeks and weeks and weeks. They’re very conservative, they had never seen a white ape before, they were horrified.

NARRATOR: But the solution to her problem was closer than she thought.

Dr JANE GOODALL: One chimpanzee, David Greybeard, actually came to my camp and he’d found some bananas, and then he came back. And then sometimes out in the forest I’d meet a group of chimpanzees and if David was there, instead of running off he just calmly sat because he knew me by now, and so the others, you know they were posed for flight and they looked at him and well, she can't be so dangerous after all. But that was after, oh five or six months.

NARRATOR: David Greybeard helped Jane think of a way to win the chimps trust. She decided to feed them.

Dr JANE GOODALL: I had the idea of putting bananas out on a regular basis because of David having stolen some. And it was he actually who brought the others, they followed him. And it took a while but eventually the whole group became used to my camp and would come wandering along looking for bananas.

NARRATOR: By feeding the chimpanzees Goodall was able to observe them closely. And it was then that she witnessed something so extraordinary it was to take Gombe from complete obscurity to scientific legend.

Dr JANE GOODALL: I remember so vividly walking through the long tangled vegetation, it had been raining, and I suddenly saw a black shape hunched over this beautiful golden colour of the termite mound and I peered with my binoculars and it was a male chimp with his back to me so I couldn’t tell who it was. And I could see his hand reaching out and picking pieces of grass and then apparently poking them at the heap, and until he moved away I didn’t realise it was David Greybeard and then he turned and looked at me. And I still couldn’t quite believe that I went up the heap, I picked up a grass, I pushed it in the hole, the termites clung on.

NARRATOR: What Goodall had seen was something we thought only humans could do, and animal creating and using a tool.

Dr JANE GOODALL: It was just so exciting, I mean at that time it was thought that humans and only humans used and made tools. Louis Leakey sent a telegram back saying, ah now we must redefine man, redefine tool, or accept chimpanzees as humans. Because up until that point we humans had been defined as man the toolmaker.

NARRATOR: Over the months and years Goodall saw many more examples of tools. They fished for ants, used leaves as sponges to soak up water. They cracked open nuts with a wooden hammer, it seemed humans would have to be redefined. But at first the idea that an animal could use a tool was so shocking that the scientific community did not believe her.

Dr JANE GOODALL: Many, many scientists when they heard that this young girl with no degree of any sort had apparently observed chimpanzees using and making tools. They simply disregarded it. There were a few who said well she must have taught them, which was, I mean that would have been very clever of me I must say.

NARRATOR: Then other scientists started to see chimps using tools throughout Africa. It led to an even greater insight. Different populations of chimps had different tools. Even when these diverse groups of chimps had the same tools they used them in different ways. So not only could chimpanzees use tools they had the beginnings of another trait we think of as solely human.

Dr JANE GOODALL: It was pretty obvious that chimpanzees have their own kind of primitive culture.

Prof MICHAEL TOMASELL (Max Planck Institute): Chimpanzees in one location use one kind of tool and in another location use another kind of tool. So that meets the minimal criterion for culture.

NARRATOR: Every group of people in the world has its own culture. At its most basic it’s the ability to create and use tools in their own way. This knowledge is then passed on to the next generation.

Prof FRANS DE WAAL (Emory University): There are some human cultures for example that use knife and fork like this culture, and other cultures that use chopsticks to get food to their mouths. Those are cultural differences, and in chimpanzees too you can see some groups of chimpanzees eat termites with long sticks and others use very short sticks and eat them one by one. And those are cultural differences in the chimpanzees.

NARRATOR: So chimpanzees use tools. They had the beginnings of culture. Suddenly it seemed as if our closest relative really was almost human. But many scientists still believed that we were fundamentally different. After all they said we can do one thing chimpanzees are physically incapable of. We can talk. Then in 2002 one scientist made a remarkable discovery.

Prof SARAH BOYSEN: I happened to be in my office while the chimps were being fed and I heard them vocalising in food burps. Chimpanzee food burps which are a natural vocalisation that chimpanzee make when they discover food or in anticipation of receiving food. And I said out loud actually, oh they must be having grapes. And then I was surprised that, at that, and came in to the feeding area to see and in fact they were being fed grapes.

NARRATOR: Sarah Boysen wondered whether chimpanzees gave different calls for different foods, if so it suggested that chimps had a form of language.

Prof SARAH BOYSEN: Yeah those are good aren’t they?

NARRATOR: So she devised a test to find out whether her chimpanzees meant what they said.

Prof SARAH BOYSEN’S ASSISTANT: Sit over there.

NARRATOR: First Boysen and her assistant recorded the calls chimps made when they were given food.

Prof SARAH BOYSEN’S ASSISTANT: Hey She come here.

NARRATOR: Then she played these calls to other chimps, like this female Sheba. She was given four photographs of food.


NARRATOR: Sheba had to choose the photo that matched the sound.

Prof SARAH BOYSEN’S ASSISTANT: Green beans excellent.

NARRATOR: This call is for oranges.

Prof SARAH BOYSEN’S ASSISTANT: Good job Sheba, excellent. Alright, good job She.

NARRATOR: Sheba and the other chimps were consistently able to choose the correct picture to match the sound.


NARRATOR: So could the calls be like words?

Prof SARAH BOYSEN: Well it may mean that there is some kind of meaning to the vocalisations they make. They could be similar to a word. They would be world like perhaps.

Prof SARAH BOYSEN: Darrel.

NARRATOR: So chimpanzees made calls that other chimps understood. They could have a primitive form of language.

Prof SARAH BOYSEN: You want one? Ooh those are lemon drops, those are good aren’t they? More?

NARRATOR: Now there was just one last barrier between us and chimpanzees. It’s what makes us truly human, knowing that other people think. Children begin to understand this very early on, it’s called theory of mind. This experiment in Germany was designed to show whether children know what other people are thinking. First the little girl played with two objects. One experimenter left the room. The girl played with a third object. Most children want to play with toys they haven’t seen so they assume other people do too. When the experimenter returned she asked for one of the toys but she didn’t say which one. So if this child has theory of mind she should give the experimenter the toy she knew the experimenter hadn’t seen.

Prof MICHAEL TOMASELL: We see one specially startling kind of skill that children at this age are already showing, and that is that even though they are showed the three objects there that the person might be focussed on, three of them this person might want, they know which one of those three the person wants.

NARRATOR: The experiment showed that very young children have the beginnings of theory of mind. Since we can't talk to them it’s harder to tell if chimpanzees have theory of mind too. But at the Max Plank Institute they’ve designed ingenious experiments to find out. Chimpanzees are very hierarchical, a subordinate chimp won’t even go for the banana when a dominant chimp is around. In this experiment a student hid a banana, the subordinate chimp could see it but the dominant couldn’t. Did she know the dominant couldn’t see the banana? The subordinate chimp understood that the dominant chimp couldn’t see the fruit, so she snatched it. But to have theory of mind chimpanzees have to know what other chimps know. This time both chimps saw the food being hidden. The cage door was closed, so that the dominant couldn’t see what the subordinate saw. A student moved the food. The subordinate stood a chance of getting the banana, because she knew that the dominant chimp did not know where the food was.

Prof MICHAEL TOMASELL: In the experiments with chimpanzees they know whether the other one has visual access or not to a piece of food. So it’s very similar to the study with children in the sense that they know what the other one can and can’t see. And in one variation of the experiment they know what the other one saw a moment ago.

NARRATOR: So does this mean that chimpanzees can understand what other chimps are thinking?

Dr JANE GOODALL: There’s absolutely no question that chimpanzees understand the needs and the emotions of other chimpanzees and respond correctly. They can even understand the needs of another human being, so clearly they do have theory of mind.

NARRATOR: Jane Goodall’s work utterly transformed our understanding of chimpanzees. Because of her pioneering research we have finally found a creature that had traits we thought were uniquely ours, tool use, culture, language, theory of mind. The final proof of our close relationship came from genetics. We share over ninety nine percent of our genes with them. But then scientists wondered if chimpanzees are so similar to us could they tell us something about ourselves? It was then we discovered they have one last trait that seemed to make them very human indeed. They had a darker more deadly side. Like everyone else Jane Goodall had always thought that chimpanzees were peaceful vegetarians, enjoying nothing more alarming than the odd ant, until she stumbled upon the truth.

Dr JANE GOODALL: I always remember sitting up on the peak and seeing a chimpanzee followed by another couple climbing up in to a tree, and they weren’t very close to me and I was peering through these second hand binoculars which was all that we could afford back then. And it was David Greybeard again and after a bit it became very clear that he was eating a piece of meat. And the female who was with him was reaching out her hand and begging, it was just very exciting because we thought that chimpanzees were basically vegetarians and perhaps consumed a few insects.

NARRATOR: And so we discovered the so called vegetarians are hunters, they’re particularly fond of baby monkeys.

Prof RICHARD WRANGHAM (Harvard University): You get incredibly excited when you watch chimps hunting, and all the sympathy that otherwise one might expect to feel for the poor prey just goes out of the window because you identify so strongly with the chimpanzee. They are so intent and they are so excited, the passion that they feel is just so extraordinary. Then they settle down in to eating it and you have a time to reflect on, on what is actually happening. And you realise that this is a very extraordinary behaviour because there is far more meat eating going on in chimpanzees than there is in any other species of primate than humans.

NARRATOR: Goodall’s discovery was a revelation. But then she found out they did something else that was far more chilling, they killed their own kind. In the sixties the group that Goodall studied split in to two fractions, Kasakela & Kahama. The rivalry between the two turned in to a bloody civil war.

Prof RICHARD WRANGHAM: It was in January of 1974 that we first had this report of one of the males in Kahama, Hodi, being attacked by a group from Kasakela. He jumped out of the tree, he ran but they got him, somebody got a foot, somebody got a hand, they pinned him down and then they beat on top of him. The attack went on for more than five minutes and by the time they let him go you could hardly crawl away. And Hodi was never seen again.

NARRATOR: One by one the males in the Kasakela group killed every male and some of the females in their neighbouring group. Only a few years before the victims had been their constant companions. In total a third of all male deaths at Gombe were at the hands of other chimpanzees. Richard Wrangham’s student Martin Muller recently discovered how brutal chimpanzees could be.

Prof MARTIN MULLER (Michigan University): It was in August of 1988, so we were with our ten males and they were patrolling. We could hear them screaming and very excited, and we heard them pounding, it sounded like they were pounding on the ground. And we realised that, that our chimps were with a chimp from their neighbouring community that they had killed and the pounding that they were doing was on his body, they were still pounding on his chest, and it was horrific. The whole front of the, of the chimpanzee was covered with thirty or forty puncture wounds and lacerations, the, the ribs were sticking up out of the rib cage because they’d, they’d beaten on his chest so hard. They’d ripped his trachea out, they’d removed his testicles, they’d torn off toe nails and finger nails, and it was clear what had happened, was that some of the males had held him down while the others attacked.

NARRATOR: Slowly it dawned on scientists that chimpanzees were not like us just because they could think, reason and use tools. They were like us because they could be cruel.

Prof RICHARD WRANGHAM: There is a sense in which this looks sadistic, the, the joy, this is kind of hard to take you know because again it’s got horrible echoes of what happens with humans at times. The males who attack, they do seem to take a certain joy in the attack, their drinking of the blood sometimes, or the biting, gripping with the teeth of the skin on part of the arm and then rearing the head back and taking the skin with it and tearing it all the way around. They look as though they’re in a state of, of intense excitement and maybe joy.

NARRATOR: Chimpanzees can be described as sadistic because they have theory of mind, they know when they’re inflicting pain. Not all animals have this ability.

Prof FRANS DE WAAL: You can not have cruelty in creatures that don’t have empathy. Ironically enough, for example a shark can do a lot of damage, it can hurt you very terribly, but I don’t, don’t think a shark can be cruel, it doesn’t have the brains to understand what the effect is of its actions. Now chimpanzees do have that kind of understanding. Chimpanzees have empathy and sympathy and so as a result they can also inflict pain on purpose I think.

NARRATOR: There is only one other animal on the planet that has a similarly dark side, human beings.

Dr JANE GOODALL: I think the sad part is that having observed that sequence of events in which the larger community completely annihilated the smaller one and then took back the territory. That just made the chimps seem even more like us than I’d ever thought before.

NARRATOR: Because of these revelations one scientist put together what would become one of the most important theories about the origins of human behaviour. Since we are so closely related Richard Wrangham believes chimpanzees can tell us about our past. And what chimpanzee aggressions seems to show is that we like them are programmed to be violent. Wrangham calls his theory the demonic male hypothesis.

Prof RICHARD WRANGHAM: The demonic male hypothesis is one that just responds to some very dramatic observations. We only know of two mammals in the world in which males make deliberate attempts to guard and kill members of neighbouring groups. And those two mammals are chimpanzees and humans.

NARRATOR: It’s called the demonic male hypothesis for a reason.

Prof RICHARD WRANGHAM: We think about this as being demonic male behaviour because of course essentially females don’t do it.

NARRATOR: In Britain men are twenty four times more likely to kill or assault another person. And two hundred and sixty three times more likely to commit a sexual offence than a woman. Ninety seven percent of prisoners serving life sentences are men. Wrangham’s theory is that violent male behaviour is the result of our shared evolutionary past. He formulated this hypothesis after he’d seen male chimpanzees killing each other at Gombe. Today his argument is accepted by many primatologists. Of all the demonic males there have been at Gombe the most demonic is Frodo.

Dr JANE GOODALL: Frodo was aggressive from a very small age, I mean when he was about three years old he started throwing rocks. If you dared to touch a rock he would pick up a bigger rock and throw it again and again. Frodo was a real bully.

NARRATOR: In 1998 Frodo deposed his own brother and became the dominant male. From the start it was clear that Frodo would rule through brute force. But there was a twist to his aggressive strategies that impressed all the other chimps, he attacked Jane Goodall herself.

Dr JANE GOODALL: Frodo singled me out, none of us know why, but from very early on he singled me out and he didn’t just push me over he would come back and then stamp on me again, maybe three times in a row, and sometimes drag me. He’s dragged other people, he’s stamped on other people but he has a special expression on his face for me, we’ve all noticed it, and we don’t know why.

NARRATOR: Not only is Frodo the most powerful chimpanzee at Gombe he is also its finest hunter. In four years he reduced the Colubus monkey population by ten percent single-handedly. And then Frodo surpassed himself. In May 2002 Frodo battered to death Rukia Sadiki’s baby girl.

RUKIA SADIKI (TRANSLATOR VOICE OVER): I was overwhelmed by the sudden attack. The chimpanzee started unwrapping the cloth I’d tied my baby to my back with, and then ran off with my child.

NARRATOR: Later Frodo was seen sitting in a tree. As the park wardens approached the chimp ran in to the forest. The baby’s body had been gruesomely mutilated. Miasa’s death led to a vigorous debate, was Frodo human enough to be charged with murder? Some people said Frodo should be put down.

Prof SARAH BOYSEN: Someone’s child died, you know that’s, that’s just a horrific thing to have witnessed. So I guess I would be in favour of some intervention by humans. We’ve intervened there in all kinds of ways for forty years so we intervened when they were sick, we’ve intervened when they needed food, it seems appropriate to intervene when there is a murderer among them.

NARRATOR: Others argued that he was just an innocent animal.

Dr JANE GOODALL: It’s always interesting to me, it’s rather like the attacks made by mountain lions in, in America, that when a wild animal kills a child there’s this outrage and you know let’s kill the animal. But if you compare it to the number of cars that kill children, if you think about human warfare it’s such a tiny percentage that are ever killed by animals. Even when you live in the animals’ habitat.

NARRATOR: So had Frodo behaved like a predatory animal, or was this a partially human act, a murder? There is a third possibility every bit as disturbing, which could call in to question some of the observations made over the past four decades at Gombe. Deep in the heart of the Congo in an area known as the Goualogo Triangle, a young American scientist has recently begun to study a group of chimpanzees. These animals could challenge much of what we have learned about the chimpanzees at Gombe, and in particular the demonic male theory.

CRICKETTE SANZ ( Washington University): I don’t even know how I can describe it because being a primatologist you’d hope to find a place like this. It was like nothing I had anticipated or expected, the chimps came in and they called others in, so three chimps became fourteen chimps and they were all circled around us in the canopy vocalising. And like this female some of them were very calm, they just sat and watched us but others were leaning forward, some would move closer in the canopy, climbing down to get a better look.

NARRATOR: Crickette Sanz realised there was something special about these chimpanzees, they’d never seen a human being before.

CRICKETTE SANZ: The Goualogo Triangle is very unique in that we’d never seen another human, we’ve never seen a camp, we’ve never seen machete cuts, other than the modest cuts that our trackers make, there's no humans there and so for probably hundreds of years these chimps had not had to coexist with humans. It’s amazing, it’s unreal.

NARRATOR: The chimpanzees of the Goualogo are like those at Gombe, they too use tools and they have their own culture. But there is one crucial difference, they are not as aggressive.

CRICKETTE SANZ: So far we haven’t seen any abnormal levels of aggression, we’ve never seen chimps killing other chimps. We haven’t seen highly elevated territorial disputes. If I had to guess I wouldn’t expect to see it.

NARRATOR: Yet when Sands told the scientific community about her chimpanzees they said she had to be wrong.

CRICKETTE SANZ: Other scientist have responded to our not seen lethal rating in the chimpanzees of the Goualogo Triangle as being a product of their not being habituated to our presence.

NARRATOR: The irony is that once the scientific establishment did not believe Jane Goodall’s reports of meat eating and violent chimpanzees. Now few believe a researcher who says apes will not be as vicious as other scientists suggest. But some began to wonder whether the demonic male hypothesis had overstated chimpanzee aggression.

Prof ROBERT SUSSMAN (Washington University): I think the demonic male hypothesis is basically a speculative idea about how the relationship between chimpanzee and human behaviour might have evolved. And I think it’s actually, actually wrong. I think by saying that humans for example have a propensity for aggression or chimpanzees have a propensity for aggression is saying very little, because all animals have a propensity for aggression given different circumstances. And what’s really interesting and important is understand the circumstances.

NARRATOR: The place where most violence in chimpanzees has been witnessed is Gombe, and the circumstances are indeed special.

Prof ROBERT SUSSMAN: Out of the ten to twenty cases of killings that were done most of these have been from Gombe, and most of the actual observed ones, the ones where people have actually seen the chimpanzees kill one another had been from Gombe. And that’s an interesting observation because at Gombe there’s been some major changes in the habitat and the circumstances over the years.

NARRATOR: Once Gombe was surrounded by forest but now the trees have been felled. There is a village within the park which is expanding, refugees surround it. The chimps are completely cut off from the rest of the rainforest. Some fear they could become extinct within fifteen years.

Prof ROBERT SUSSMAN: You could look at this much like an animal group that’s living in a very stressful environment and in, in some ways it’s very much like the difference between a naturally living population and one living in a zoo.

NARRATOR: Because of human encroachment some of the chimps are already dying. They’ve caught diseases from the large numbers of people who have visited, filmed, followed and fed them for forty years. Even the mighty Frodo was laid low. There are now six long term chimpanzee study sites including Gombe. The chimpanzees in every one of those sites are aggressive. Every site also suffers from human pressure.

Prof CHRISTOPHE BOESCH (Max Planck Institute): People are to realise that this encroachment that human do on nature is also doing on the home of many animals who live there and including chimpanzees or any other animal species, and it can present a tremendous stress on them.

NARRATOR: Chimpanzees in these long term study sites are losing out to logging companies and to poachers who invade the rainforest and snare them for bush meat. Those that survive are left with injuries that can alter their behaviour.

CRICKETTE SANZ: You look at the level of snare injuries at some sites and they’re quite high, sometimes up to one in four chimpanzees in a community have a snare injury, and a snare injury is serious. I mean this could be missing a hand or a foot, and this is going to change their behaviour.

NARRATOR: Some now believe that stress caused by humans can make chimpanzees more violent.

Dr JANE GOODALL: I didn’t see aggression to start with. There’s no question that chimpanzees become more aggressive as a result of crowding, as a result of competition for food. It took a long time at Gombe before I realised how aggressive chimpanzees could be.

NARRATOR: Everyone accepts that chimpanzees can be aggressive. But evidence from most long term sites suggest that even by chimpanzee standards the violence at Gombe has been excessive. Christophe Boesch works in the Tai Forest on the Ivory Coast. His site suffers from significant human disturbance, a civil war. Yet the chimpanzees do not seem to be as aggressive as those at Gombe.

Prof CHRISTOPHE BOESCH: I have not seen this kind of killing in Thai Forest. This violence is not always present. Richard Wrangham’s ideas originates from his observation in Gombe, and it’s obviously something extremely worrying to see the chimpanzees killing other chimps. But I also think we need to take in account in this thinking these huge behavioural diversity that exists between chimpanzee population.

NARRATOR: This was the heart of the question, was there something about Gombe that led to such high levels of aggression? Some now suggest that there was. At Gombe the chimpanzees were fed so that they would quickly lose their fear of human beings and could be studied, feeding had an enormous impact.

Dr JANE GOODALL: When we were feeding bananas on a daily basis to anybody who came along there was very unusual aggression between the chimps, and in addition it was attracting the baboons. And although baboons and chimpanzees fight over palm nuts in a ripe palm tree, quite often actually, but this was, was again creating real tension and aggression between the chimpanzees and the baboons, the whole situation was terrible.

NARRATOR: Goodall realised she’d heightened the violence. She installed a number of systems to try and reduce the aggression. Most relied on putting bananas in boxes, and then opening the bananas one at a time to ensure all the chimps had a fair share of fruit. But the chimpanzees knew the boxes contained food and they became increasingly aggressive. Goodall fed the chimps for fifteen years continuously and then sporadically for another twenty two.

Dr JANE GOODALL: Banana feeding finally stopped about two years ago.

NARRATOR: Feeding may have changed the behaviour of the chimpanzees to such an extent that some have questioned the data on aggression collected at Gombe.

Prof ROBERT SUSSMAN: Interestingly enough she had collected a lot of data before she started provisioning the animals and data outside the provisioning area. And her first fifteen years of study she actually stated that the chimpanzees were much less aggressive than they were after provisioning. She stopped using that data because it just didn’t, or seemed to be the same as the data after that, that period of time.

Prof RICHARD WRANGHAM: Gombe was the first chimpanzee site to develop a really rich account of behavioural observations and it was made possible by techniques that nowadays we don’t carry out. Giving some food to bring the chimps to a predictable place and even touching the chimps and interacting with the babies. Those gave wonderfully intimate details of chimpanzee lives. But in the subsequent years people have entirely abandoned those practices.

NARRATOR: Gombe is an extraordinary place. It had taught us much about chimpanzees and how close they are to humans. But some now think that the actions of the scientists themselves may have altered chimpanzee behaviour. This could have seriously implications, particularly for the demonic male hypothesis. By basing their ideas on what they’ve seen at Gombe some think the scientists may have overstated chimpanzee aggression and thus what they can tell us about ourselves. This is a controversial suggestion and not everyone agrees.

Prof RICHARD WRANGHAM: You know when it was only Gombe that was the source of information about actual killings then people could say oh well Gombe is all special and peculiar, you know they had, they gave bananas to them for a few years so that would have caused them to kill each other, which to some of us seems a little bit absurd. You know I think what we’re seeing at the moment is a ratchetting up of the empirical evidence to the point where everybody agrees that this is a phenomenon that you just have to really grapple with.

Prof ROBERT SUSSMAN: I don’t think there’s very much evidence for the demonic male hypothesis, it’s actually based on a number of instances of chimpanzees killing one another in certain circumstances and the hypothesises are based on the fact, or on the idea, that chimpanzees and humans share genes that are similar that cause them to be violent. I don't think that’s very explanatory or helps us understand violence in chimpanzees or in humans.

Dr JANE GOODALL: It’s very hard to look back with hindsight and say oh well I would have done it differently. If I had gone to Gombe and had access to information about the effect of feeding bananas on wild chimpanzees I wouldn’t have done it.

NARRATOR: This may be the supreme irony of Gombe. In our desire to understand ourselves we may have distorted the very animals we were using as a mirror. We do share much with our closest ancestors, but ultimately chimpanzees are not windows in to the human soul.

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