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Dr. Richard Wrangham:
Once you are able to control fire to the point where you can use it both to cook and to keep yourself warm, that means that you are shifting from a chimpanzee-like animal to a human-like animal.
Gerry Ellis:
Welcome to talking Apes. July 14th is World Chimpanzee Day, and to celebrate, we’re talking with Dr. Richard Wrangham, Harvard University primatologist and chimpanzee expert. So who are we? That’s the question that has tortured humankind sense – well, since apes like us became human, I guess. There’s a biological Us and there’s a cultural Us and the ongoing evolution of each is inexorably linked. That evolution and the connection to our living great ape cousins, the gorillas, orangutans, and particularly the bonobos and chimpanzees, has consumed Richard’s curiosity and intellectual perambulations for more than a half century. Richard’s research and writings have focused on great ape behavior, human evolution, aggression, and – get this – cooking. Yes, cooking. We’ll figure that one out. We’ll spend some time around the evolutionary fireplace with Richard, talk about his book Catching Fire, and explore cooking and how the fire that made it possible may have also made Us possible.
Gerry Ellis:
Hi, I’m Gerry Ellis and this is Talking Apes, where we explore the world of apes and primates with experts, conservationists and passionate primate lovers from around the world. Talking Apes is a podcast that gets to the very heart of what’s happening with and to apes like us. The Talking Apes podcast is made possible by generous support from listeners like you to nonprofit GLOBIO.org.
Gerry Ellis:
Richard Wrangham, welcome to Talking Apes. I am super excited to have you on and especially since we are celebrating World Chimpanzee Day and I’m looking forward to our conversation.
Dr. Richard Wrangham:
Well, I think it’s wonderful that you get to talk to ape people and spread the word about apes. It’s a privilege to be here.
Gerry Ellis:
Well, I can’t think of a more appropriate ape person to have on today than you. You’ve spent half a century – God, that’s an amazing period of time – half a century thinking about us and our ape cousins and how who we are and what they are. And that’s where I would like to start the conversation today. Especially for those who are listening to this and may not be familiar with all of your work or maybe even any of your work, could you give us that hour and a half recap of your life? Cause that’s how long it would probably take, but maybe we can cut it to 5 or 10 minutes. But anyway, how did this all get started? It launched many, many years ago, so maybe you could take us back to the beginning and your connection to especially chimpanzees.
Dr. Richard Wrangham:
Well, I am an old fashioned naturalist at heart. I just love to be in nature watching animals. Could be birds, could be mammals, could be insects. And when I grew up, I seized every opportunity I could to find ways to just indulge my aesthetic pleasure, which increasingly became an intellectual pleasure in enjoying the natural world. And by the time I left university, having studied zoology at Oxford University, I wanted to do a PhD studying animal behavior. And I was incredibly lucky because my tutor at Oxford was a man called Harold Pusey who had a daughter called Ann Pusey who was at that point just starting a career working in Gombe in western Tanzania for the already pretty famous but still very young Jane Goodall. So Jane Goodall is the famed documenter of chimpanzees who has been working for 60 years. I’m a “Johnny come lately,” 50 years.
Dr. Richard Wrangham:
But even then it was clear it was gonna be a privilege to work with Jane Goodall in Gombe National Park with wild chimpanzees and working with her meant going out and every day having the opportunity to watch chimpanzees moving around in the wild and behaving. And that is basically what I have done for the rest of my life. So I literally did a PhD, I studied a few other animals, I studied some monkeys, vervet monkeys in Kenya. I studied Gelada baboon-like animals in Ethiopia. I spent a year living in the Congo with people living in a non-state society essentially. These were Efé – nowadays we don’t like to use the word pygmies because it sounds somewhat demeaning, but these were these very small statured people, and that was just totally fascinating living in a forest, and not totally different from forest I had known. But I rapidly came back to chimps and I worked in a university and every year until this lockdown year, I would find myself in Africa, mostly in Uganda, where I founded a new long term research study of chimpanzees in 1987. And I continue to go there as often as possible and catch up with those chimps. So it was a journey that I feel incredibly lucky to have been part of because I think all of us are interested in the human condition and ultimately I think there are very few ways to get as fascinating insights about the really deep questions of who we humans are. Very few ways to get it as much as you get from watching chimpanzees.
Gerry Ellis:
And it’s those deep questions that I kind of want to dig into because as we were chatting about before we started recording, you often hear this phrase: you are 98% like chimpanzees or 98% chimp. And there’s tee-shirts, and the media loves to say that, and in fact Jane often says that, and I guess for a very long time I’ve just sort of thought about it as, yeah, we’re 98% chimpanzee. But in looking at the history of your work and where you have been pushing the conversation, and I do say pushing because I think you have often said some things that others have went, “wait a second, I’m not sure we should be having that conversation, that’s not quite on track with evolutionary thinking at the moment.” There’s much more to that 2% that separates us from chimpanzees as human beings or the creature that we have become.
Gerry Ellis:
And that especially hit me when I was reading Catching Fire, your book about cooking, which came out roughly a decade ago, I think 2009. I was just rereading it over the last few days. It really changed the way I think about who we have become because many of the things that you go on to do – Demonic Male and looking at aggression and now The Goodness Paradox, your newest book, and looking at this aggression and war, and maybe we can touch on some of those, but it seems to all come back to this moment of energy and energy and cooking. And you could explain it far better than I. Maybe we could start there and talk about why that was maybe such a sentinel moment in separating, in creating that 2% difference between us. Otherwise we might all still just be another chimpanzee version.
Dr. Richard Wrangham:
You’ve raised two big questions in the last minute and I’d love to just begin by thinking about the 2% because that number means incredibly little on its own. I mean, what it means depends on how much the 2% matters. And we have no way of judging that arbitrarily. I mean we are 50% related to a banana.
Okay? So we’re not yellow and banana shaped <laugh>.
These percentages only mean something once you understand the way genetics work and so on. But the really important thing about the genetic discoveries which began in the 1980s and then got really firmed up over the next 15, 20 years, the really important thing was not how much of our genes differ between us in any particular species like chimpanzees. It was to show what the order of evolutionary relationship was with different species. And the very, very dramatic finding that was completely incredible to a lot of people initially, which it first came out in 1984, was that chimpanzees are more closely related to humans than they are to gorillas.
Now the astonishing thing about this is that chimpanzees and gorillas look extremely similar to each other. In fact, they are so similar that people have sometimes been unable to decide whether a particular animal is a chimpanzee or a gorilla. There was this famous thing called the Koolakamba, a population of western apes in Gabon in the 19th century. And some people said it was a gorilla and some people said it was a chimpanzee, and that’s how similar they are. If you are a big chimpanzee or a small gorilla, you look pretty similar to each other.
Dr. Richard Wrangham:
Well, obviously, what you would expect is that if you look at the DNA, you would find that the chimpanzee and the gorilla have much closer DNA to each other than they do to their relatives like humans. And yet the initial discovery in 1984 was that chimpanzees are actually more closely related to humans than they are to gorillas. What did that mean? Most people interpreted it as the geneticists have got it wrong, it can’t be right. And for the first – I can’t remember – 10 years or so, there was some pretty intense debate where some people just asserted, that’s got to be wrong. It’s obvious that chimps and gorillas are so similar, they must be each other’s closest relatives. But the data just kept coming in better and better, not just mitochondrial DNA, but lots of different genes on the nuclear genome and then the entire nuclear genome.
Dr. Richard Wrangham:
And finally it was just completely clear, absolutely chimps and humans are more closely related to each other than either of them is to gorillas. So what that meant was that you could now think about the common ancestor of chimpanzees and humans and think what was that like? And because that common ancestor’s closest relationship to any other animal was to a gorilla, and because it was the ancestor of chimpanzees that looks so similar to gorillas, then the obvious answer is that that common ancestor of humans and chimpanzees was in the chimpanzee-gorilla mold. It was a little bit smaller, it would be more like a chimpanzee. If it was a bit bigger, it’d be more like a gorilla. In other words, that thing that gave rise to humans all those years ago, which we can now say is around 6 or 7 million years ago, if it was a bit smaller, it was more like a chimp, it was a bit bigger, it was more like a gorilla.
Dr. Richard Wrangham:
So that’s what was so exciting. Less than 50 years ago, just over 40 years ago, we discovered that we were descended from a species that was very, very similar to the chimpanzee-gorilla. Now the question was how big was it? Well, we now have a pretty good fossil record of the descendants of that species. It doesn’t go all the way back to 6 or 7 million years ago, but you’ve got some fragmentary stuff that goes pretty close to that. And you’ve got really good stuff by the time you get to 3 million, 3 and a half million years ago. And they’re all pretty small. They’re all much smaller than chimps, so they’re more like chimps than gorillas. The ancestors you can infer, and maybe they were a little bit different from chimps because maybe they were smaller than chimps, so they weren’t identical to chimps necessarily. But it means that if we look at chimps now, they were remarkably close in what they looked like and their genes to the ancestor of us all 6 or 7 million years ago. And of course the reason that we have to go through all of this fascinating genetic inference is because we don’t have direct fossils. These were undoubtedly species that lived in forests, and forests tend to have soils that will destroy fossils. They’re too acidic for the bones to survive in general.
Dr. Richard Wrangham:
So the genetic evidence has been really crucial and it wouldn’t have mattered whether it was 2% or 5% or 1% or what. The important thing was that we are more closely related to chimps than chimps or us are to gorillas. So that was what was so exciting and that all of a sudden put the spotlight on chimpanzee behavior in a way that previously was just a very diffuse kind of understanding of, well, we are descended from great apes, we are, if you like, great apes ourselves. So wouldn’t it be interesting to see what we do compared to the great apes? But now we can say, hey, these chimps are very, very similar to our ancestors. Well then we go to what Jane Goodall had already discovered that the chimps were, and particularly in the male behavior, astonishingly similar to some of the unusual behaviors of humans. They were hunting other animals and meat, eating them and sharing the meat.
Dr. Richard Wrangham:
They were using tools, they were going on raids to attack members of neighboring groups. I mean, these are all things that we thought of as uniquely human and now they turn out to be in the species that we think was a pretty darn good model for our ancestors. So it all contributes to giving a sense that it’s much more than a vague general resemblance to an ape. We’re not just looking at gorillas, bonobos, chimpanzees, orangutans and saying, well, they’re all apes. Can we average among them and somehow produce some kind of concept of where humans came from? No, we zero in on chimps. Now you said, what about the diet? What about food?
Gerry Ellis:
Yeah, where’s that separator then if we’re sitting there in Gombe and we’re looking at a chimp, as you and I have both done, what separates – I mean, you look at them and there’s a lot to look at that is similar and behaviorally, as you just said, they hunt and they do these things. So what is it that we should be looking at that somehow took us from that small little creature connected 3 million years ago or two and a half million years ago? What should we be looking at? What should we be thinking about?
Dr. Richard Wrangham:
Well, you already said what I think of as a very, very big contributor to the answer maybe in my mind. I said I really think it was the answer and that is cooking. And let me just amuse you by saying how stupid I was to be so slow to think about this. Because when I went to Gombe in Q’s wake, as it were, and I spent a year being a research assistant to Jane, and that was wonderful because I studied the relationships among some pairs of siblings and it gave me an opportunity to think about what I would like to study for myself. And during a year what you see, as I’m sure you’ve seen in Gombe, is that as the different fruits and the different foods change over the year – they change in abundance, they change in distribution. And the chimps, their behavior obviously changes in response.
Dr. Richard Wrangham:
Sometimes they’re all gathered together in a great big feeding clump where there’s just a tremendous amount of food, and then sometimes it’s scattered and very hard to find and they disperse into isolated units and so on. So I said to myself, well, nobody has really got together a story of exactly how the changing pattern of food abundance and distribution affects their behavior. So let me study that. So I became just fascinated in the diet and in the process of doing that, I tasted all of the things that chimpanzees ate and I learned what I could eat reasonably comfortably. I mean there are wild raspberries, so some things are totally nice and there are other things that are pretty difficult to eat and certainly difficult to fill your stomach with. But nonetheless, I felt I knew enough to be able to maybe survive on the food.
Dr. Richard Wrangham:
And so I went to Jane Goodall and said, look, I think it is just fascinating to see if a human could survive on a chimpanzee diet. Do you mind if I do that? And I spend a few days just living out in the wild and trying to be a chimp. I really wanted to get under the skin of a chimp. And she said, Yeah, okay, that sounds crazy. It sounds really stupid, but if you wanna do that, you can do that. And I said, okay, well great. And by the way, I wanna make it sound authentic, so I wanna be naked, I don’t want to deal with clothes. And she said, well okay, but I think no, you’ve gotta be decent, so you’ve gotta wear a line cloth. Oh this is pretty generous of her to allow this kind of craziness. I mean you have to understand I was 22 or something and I said, oh well if you’re not gonna take it seriously, if it’s not gonna allow me to take it seriously, I’m not gonna do it. So in my memory, I think really what was going on of course was I wanted an excuse not to do it, even though I thought it’d be fascinating because it would’ve been incredibly uncomfortable.
Gerry Ellis:
I can’t even imagine.
Dr. Richard Wrangham:
So I didn’t.
Gerry Ellis:
I can’t even imagine.
Dr. Richard Wrangham:
So I didn’t do it. But it is just to say that I was thinking about the fact that knowing all the chimp foods and knowing that many of them were sufficiently palatable to be able to eat them, that I thought I might survive. Cut to 25 years later, and I am thinking about the difference between humans and chimpanzees in terms of, again, this very fundamental aspect. And I’m sitting in front of my fireplace in a home in New England and I’m looking, staring at the fire and I’m thinking, wait a minute, how long is it that I’ve gotta go back in my ancestry before people did not stare out looking at a fire, which led me to think about how long is it we’ve gotta go back before we can get to somebody who didn’t cook their food? And that basic very simple question led me extremely quickly to what I think is the right answer.
Dr. Richard Wrangham:
And that is the beginning of the genus homo, which is 2 million years give or take a year or two. I think that what happened is that 2 million years ago we changed from a basically pretty chimp like animal to an early kind of human because what you see at that point is in the space of a few hundred thousand years, a very dramatic shift from a relatively small, slightly smaller than chimp size animal with a head, and that means both the brain and a jaw that is basically pretty chimp like, and shoulders that are chimp like, arms that are chimp like, not chimp like is the fact that they could walk upright and did a lot, but at the same time they were still clearly very good at climbing. So it’s not unlike a chimp. The way to think about these australopithecines, which is what we’re talking about, gave rise to the genus homo around 2 million years ago.
Dr. Richard Wrangham:
You roughly think about them as a chimpanzee that was standing upright a lot and by the way had changed their teeth a little bit so they were good at eating roots. And all of a sudden in terms of the paleontological eras, in other words, still half a million years ago, something like that, half a million years it took, you changed from that kind of species, chimp like things standing upright, into a crude relatively small brained but big, robust version of humans, which we call homo erectus. The first erect human meaning standing upright. And the classic thing to say about them is that if they could have gone into a clothing store on Main Street, they could have picked clothes off the peg, which was not true of a chimpanzee. They could pick our clothes off the peg, they need a little bit of filling out on the shoulders and so on, but they’re our shape and size roughly.
Dr. Richard Wrangham:
So that was something that changed pretty dramatically, and I think that it was the discovery of the control of fire was responsible for that. And I’m now amazed that people had not thought about that subsequently prior to my making the argument in a big way. A lot of people have said how extremely stupid not to have thought of that, to quote Thomas Henry Huxley responding to Darwin. And yet we do not have the absolutely killing evidence about it still. So here’s why I think it happened, the three big pieces of evidence: first of all, the mouth had changed to accommodate a softer type of food. The teeth became smaller, the jaw became smaller, the mouth, the whole mouth became smaller. So instead of eating relatively tough foods, when you got to the genus Homo, these were individuals that were eating something that was relatively easy to chew with smaller, blunter teeth, smaller mouths, less muscular jaws.
Dr. Richard Wrangham:
Secondly, the whole of the gut was much smaller. Nowadays our gut is about two thirds of the size it would be if we were in great ape. Maybe it was three quarters of the size, I don’t know. But it was quite a bit smaller to judge from the changes in the bones, the flattening of the ribs, the narrowing of the pelvis. It was carrying a smaller gut altogether. And the fact that we now have a smaller gut is explicable by the fact that we cook our food, which means that the food is more digestible, it is easier to digest, the gut doesn’t have to work so hard, you don’t have to hold so much material in the gut. And then the third reason is that this was the time when we stopped having our adaptations to climbing in trees. So no longer were our ancestors really good at climbing in trees like chimpanzees are, or these australopithecine descendants of a chimpanzees-like ancestor which had strong long arms and great mobile shoulders and tremendous upper body strength which would enable them to swing up into trees and climb around in them very easily.
Dr. Richard Wrangham:
The fact that our Homo erectus ancestors had lost those adaptations meant they had to be sleeping on the ground. They could no longer climb up into trees in the way that chimps and gorillas and so on do and make their nests every night. Well if they were sleeping on the ground, how did they defend themselves? I mean, nowadays you’ve gotta be a complete lunatic to go off into the Serengeti or wherever it is and just curl up on the ground and hope that nobody finds you in the night. It’s only I think when you’ve got fire that you can protect yourselves. And in fact, we even know that from people nowadays because the few times when people living as hunters and gatherers have been recorded as been killed by predators is when for some reason their fire goes out and they don’t have a fire and the predators can sneak up on them.
Dr. Richard Wrangham:
So I think the small mouth, the small gut and the commitment to sleeping on the ground is all evidence of using fire. And the critical thing is the cooking. Because once you cook then many things happen. You get a better quality of food, you get a greater variety of food because there are things that were previously poisonous or bacterially dangerous than you can eat. You have very significantly much less time chewing. As a photographer going out to Gombe, you probably were hoping when you first went there to see chimps sitting around playing with tools all the time and doing wacky things. But in fact, of course, what do they spend all their time doing? They’re up in a tree chewing.
Gerry Ellis:
And that’s exactly why as you went to Jane and said you wanted to get naked and go eat that food, I said to her, they’re always up there, how do you feel about me going up there? She says, I don’t know, I haven’t been up there with them. They may throw you out. And in fact that was my best opportunity to film them in the trees was when they would find a big fig tree that was in fruit. They would all be up there sitting on a branch eating figs and just gorging and gorging and gorging. Or as you alluded to just a minute ago, if they were frightened, that was their first response, to shoot up a tree. The big males would sort of take their stand on the ground to check out what was going on, but mothers and infants were boom, they were up a tree for safety. Yeah, fire. I mean it really makes sense that fire changed that dynamic.
Dr. Richard Wrangham:
What’s so dramatic is just the amount of time they spend chewing, and somehow I’d taken it for granted for being with chimps. But then you actually start thinking about it and of course there are very good time in motion studies of all sorts of people around the world in non-state societies and in state societies, hunters and gatherers, horticulturalists, pastoralists and so on. And it turns out that humans are extremely consistent. I mean it’s around 5% of the day that we actually spend chewing our food. So it’s less than an hour a day, but how much are chimps doing it? Well, in Gombe, I found it was on average more than six hours a day. In the place where I’m now studying chimps in Western Uganda, in Kabale, it’s more like four to five hours a day, but it’s still a lot more than humans. And all of a sudden you’ve got all this spare time.
Dr. Richard Wrangham:
And then here’s another thing, when you’ve got fire, then you can keep warm at night. So you don’t need to be covered in hair. That means that during the day you can take a lot of exercise and shed the heat build up as your muscles are doing all that work. So you can walk for long distances or you can run and that is only possible because you can shed the hair that you would otherwise have needed to keep you warm at night. So there’s a lot of consequences once you are able to control fire to the point where you can use it both to cook and to keep yourself warm, that means that you are shifting from a chimpanzee-like animal to a human-like animal. And I think that was the biggest thing that happened 2 million years ago.
Gerry Ellis:
In a weird way my brain goes to maybe that is why we all get around a fire, we all stare into it. Maybe there’s something really ancestral about that mesmerizing effect. It changed us.
Dr. Richard Wrangham:
I love the fact that you can now buy DVDs of just a fire and there are people who just plug it in and they’re just watching a fire. I think you are absolutely right. It’s hard to resist the idea that our psychology, and we’re talking here about emotions, much more than reason, our emotions have been shaped so that we really enjoy just being around a fire because it’s safe and it’s a source of so much importance to us. And by the way, sort against that in a way is the fact that if you ever live in a non-state society, an open air society, you will have known that you smell smoke all the time and that you spend your life around that fire dancing to try and get away from the smoke. So we are drawn to fire but we still don’t like smoke.
Gerry Ellis:
It is an interesting smell. I mean, I have to admit one of my absolute favorite things is flying back into the tropics, and especially if I’m landing in a Cameroon or a Gabon or Congo or something, and I fly in during the evening and you get off that plane and it’s that warm humid air with that acrid smell of smoke because there’s fires going on everywhere and it’s just, to me that is a sense of the tropics that I feel like I’m there, back in the tropics because of that.
Dr. Richard Wrangham:
Well I was just gonna say, I mean you’re right that I think it is an atavistic part of humanity that we would’ve lived with smoke for 2 million years. Now there are people who still challenge my dating at 2 million, and I’d be amazed if it’s wrong, but whatever it is, it’s a long time that we’ve been living with smoke. It is a really human feature.
Gerry Ellis:
That takes me to the next thought because as you were describing people gathering around a fire, I was thinking also it has this social value. If you’re sitting around a fire in the evening and somebody shows up, whether friend or a stranger, I mean one of the first things you do is you kind of welcome them into the glow of the fire, not only to see them – and people almost always invariably, no matter what the temperature is, it seems like they always back up to the fire. And then there’s this socialness, this gathering that goes on around it. And it seems like an interesting bridge when I think about some of the other work you’ve done around aggression and social evolution is that this fire became that hub for a lot of those things to happen. And if you’re sitting there, you’re trying to communicate. So language – is language born out of that fire? I mean, all those questions pop up in my brain. Do you have any thoughts on that?
Dr. Richard Wrangham:
Well, one thought is what an anthropologist called Polly Wiessner found out. She lived with the Ju/’hoansi Bushmen of Southern Africa, Botswana in the Kalahari Desert, and she recorded conversations all day. And the short story is that it is around the fire that all of the most interesting, subtle, informative conversations happened. That’s where people reflected on their relationships with people in other camps. That’s where they told the stories about their ancestors, that’s where they passed on the law about the wisdom of the ancients, the cosmology of the group. Whereas during the day the conversation will be relatively brief and more to do with immediate directions. I come over here, where’s the arrows? Whatever. So there was this great connection between fire and language in those people. And that seems to make every sense. I can imagine that being true of humans in general. I do think it’s absolutely right that fire would’ve been so important at night for people to be able to gather around it, that there would have been some kind of evolutionary change towards social tolerance about easy companionship around the fire.
Dr. Richard Wrangham:
I don’t know how big the change would’ve had to have been because as you know chimpanzees, they are famously more aggressive than bonobos and they are in some ways more aggressive than humans. But nevertheless, they can spend hours or days in a very relaxed mode. And some of my fondest visions and memories are of being with a group of chimps who’s mostly asleep on the ground, many of whom are in physical contact with each other just breathing extremely comfortably, maybe idly playing with the fingers of some neighbor, infants wandering around, just rolling on others. It’s just a wonderful bucolic scene of calm and enjoyment and pleasure.
Dr. Richard Wrangham:
So it’s easy to think that you can move from that kind of relaxed sleeping day group into just lying around a fire. But it would’ve been very important to make sure that those groups were not disturbed by any individual who was constantly trying to irritate others. I don’t what they should have done, but maybe some juveniles would want to pick up a flaming ember and wave it in someone else’s face or I don’t know it, it is easy to be too speculative, but I take the general point that the fire would’ve embedded that kind of social tolerance that you see expressed among chimpanzees on lazy family afternoons when they’ve got full bellies. Not a huge change, but a comfortable sort of shift in the right direction.
Gerry Ellis:
I heard you talk about – I can’t remember the location, but I heard you discussing that the energy need also that came out of cooking for brain development. And I thought it was fascinating that the sheer energy that our brains use, and again going back to that, looking at those differences between ourselves and chimpanzees with these big brains that we have. Or energy – maybe not big brains as much as energy consumptive brains.
Dr. Richard Wrangham:
Yes, right. Well, I mean this is a very interesting story because we know quite a lot about the evolution of brains because we have a sufficient number of skulls in the fossil record that we can calculate the volume of the skull and relate it to the size of the body and we can be pretty confident that the volume occupied by the skull is a very good measure of the size of the brain from everything we know about primates and humans. So the story is that the brain size remains very chimp-like, just a little bit bigger than chimps, but only five, 5%-10% bigger, that sort of thing, throughout the last 6, 7 million years until 2 million years ago. And then after around 2 million years ago, the brain started its steady rise and it carries on rising throughout much of the last 2 million years as the simple story. And so why does the brain get bigger? Because this is obviously a fascinating question from the point of view of thinking about the increasing intellectual abilities of our ancestors.
Dr. Richard Wrangham:
And very often people think about this in terms of, well what are the advantages of having a bigger brain? That’s the classic way to think about it. And people think, oh well, it would really have paid to be able to figure out how to stalk prey animals or how to get the best foods or whatever. But actually most people I think nowadays recognize that the kinds of advantages that would’ve applied to humans would have applied to any species. Chimpanzees – they could do with a bigger brain. If you think that the brain is there, as most people now do, to help solve social problems, well chimpanzees have lots of social problems. So what is the reason that some species can have a bigger brain than others? Answer is, can they fuel it? Can they afford to be able to provide the fuel for the brain? And the reason for saying that is the brain is not merely a very hungry tissue that requires a high proportion of oxygen compared to its weight, compared to most other organs in the body, but also you never can turn it off. It’s not like a computer, turn the computer off, you can turn it on again, you turn the brain off, you can’t turn it on again. Sorry. You’re dead.
Gerry Ellis:
That’s true. Yeah. I never thought about that.
Dr. Richard Wrangham:
And so how much energy do our brains use? It is close on a quarter of basic metabolic rate. So if you are not doing too much about every fourth hamburger you eat is just for fueling your brain. Well, that is a challenge because all animals are energy limited. The thing that animals are kind of designed to do is to extract energy from the environment and ultimately convert it into babies. That’s the way evolution works, convert the energy into babies that survive and reproduce themselves. So how can you afford to put more energy into your brain and less into your babies or your own body? Well, it helps if you can get a new supply of energy and then you can all of a sudden say, Well what are I gonna do with this new energy? That’s a sort of casual way to think about it.
Dr. Richard Wrangham:
And that’s what happened when our ancestors learned to cook. They were able to get increasing supplies of energy available to divert it to the brain. Why is that? It’s very much because the fact that they were eating more digestible food meant that their guts did not have to work so hard, and the gut is another expensive organ. So the gut was able to get smaller. I mentioned earlier it’s about two-thirds of the size it would be if we were a great ape. All of a sudden, you’re saving all that energy that would be used to maintaining the gut. What are you gonna do with it? And in the world that our ancestors lived in, for some reason they were able to move that into the direction of the brain, fuel the brain, and that paid off better than simply having more babies, maybe because life was so competitive that you really needed to have the smartest possible babies that you could. So the steady rise in the size of the brain over the last 2 million years is a rise that is largely independent of any changes in body size. And it seems to be as fast a rise in brain size as you will find anywhere in the animal kingdom. So it may be that it is just as fast as it could be in relationship to the increasing supply of energy coming from our reducing gut size, our increasing quality of food as a result of cooking, and that we owe our abilities for poetry and photography to cooking.
Gerry Ellis:
How does that change for people now? I’ll ask the question, I’m not sure if you know the answer or not, but how does that change for people now who shift their diets radically from a cooked – cooking diet to one that is not just vegetarian but raw diets very limited diets where it sounds like we’re not talking about hundreds of thousands of years here where a brain has to develop, but still if the energy is different, is there a shorter term impact on thinking and clarity and reproduction?
Dr. Richard Wrangham:
Well, okay, so I don’t think there’s any studies of the effects of eating a raw diet on thinking, and I wouldn’t be sure how the answer would come out because the brain is a very protected organ. In other words, as if the body knows that if the brain gets too little food, well you’re in very big trouble, there’s a risk of death. So the last thing that will happen to a starving individual is that the brain will be reduced in energy supply. But there are very big short term dangers to eating a raw diet in terms of energy shortage. And the real place where this is important is with children
.
Dr. Richard Wrangham:
So there are people who, for philosophical reasons, wanted to get back to nature, that sort of thing, commit themselves to a raw food diet in a really strong sort of philosophical determination to do it. And that becomes dangerous when they bring their children in. As adults, it’s not dangerous so much as awkward. A raw diet is very short in energy. It is so short that when women have been monitored on a raw food diet they have a very clear indication of their shortage of energy in that they stop menstruating. And this is very dramatic data because the raw diets that people select are in fact incredibly high quality in the raw diet area. So they are foods that first of all they’re very often mashed up in a blender and so on. So that does a lot of the work of digestion for you. Secondly, they are foods that come from all around the world so that at any season of the year you are always getting fresh foods.
Dr. Richard Wrangham:
They often have oils and other high quality foods at relatively high level and there’s even a little bit of cooking and a little bit of heating involved. But despite all these advantages, the average woman ceases to menstruate and cannot have a baby. And that’s because of the shortage of energy. Well that’s all very well if you’re an adult, but what if you’re a child? And the answer is that terrible things that have been found with children were being brought up in the best possible motivations of the parents, but they just are misguided in thinking that a raw diet is something that humans could survive on. Then the children have been recorded dying on a raw food diet if not certainly being stunted. So it is dangerous. I personally think there ought to be a law which says that you are not allowed to feed your children on a raw diet if only to help people be alerted to the fact that it is so dangerous. And it’s an awkward thing because many people think that it is getting back to nature. All animals eat their food raw. We are an animal, why shouldn’t we eat our food raw? Well the answer is we are the only animal that has been evolved to eat our food cooked and for that reason we cannot eat our food raw. It’s really, really dangerous. So it shows what an extraordinary difference, the amazing journey we’ve come on from being a chimp like ancestor.
Gerry Ellis:
That’s that thing I was getting at in the beginning, and the hiding in the 2% is we’ve evolved to eat cook food. Therein lies one of the biggest differences. And around that all of the social context and the language and this brain development, and that takes us down a whole nother line that – we’ll have to do this again sometime, but talking about how we act as social creatures, aggression and passivity and I mean all those kinds of things they seem to spin out of that cooking context, that energy context.
Dr. Richard Wrangham:
Well a lot of it does. But of course the thing about cooking is that all of the members of the genus Homo – the genus Homo evolved 1 to 2 million years ago – it produced a whole bunch of different species. There are so many lines that people are still finding it difficult to trace exactly how they work together. But there was Homo erectus, there was Homo Heidelbergensis, there were Neanderthals, there were Denisovans, there were people in Flores Islands. You will find people who will name a dozen different species. Now according to me, all of them cooked and according to the most conservative people, definitely Neanderthals cooked and almost certainly, well, actually definitely Heidelbergensis cooked. And we’ll see about the rest if you’ve been waiting for the definitive archeological evidence to tell us. So even though cooking was very important for the evolution of our genius with its multiple species of different kinds of human, what it doesn’t do is it doesn’t help us say why Homo sapiens is different from Neanderthals and Denisovans and all of the other species. And that I think is a story where indeed we have to talk about aggression and tolerance and self domestication.
Gerry Ellis:
And that’s why we will have you back on and have another podcast. This has been really fascinating. I do have a couple of other questions if I can dig out all my notes here to bring us to a close on this. This has been really fascinating. Thank you Richard.
Dr. Richard Wrangham:
Great questions.
Gerry Ellis:
It’s an amazing conversation and first of all, I just find it fascinating that we’re the only ones who can sit around and have this conversation. I’m sure there are chimps not sitting around having this conversation. So the fact that we’ve somehow managed to get to this point is fascinating all on its own. But I wanted to ask you just in closing a bit, after 50 years and as we started, you said that you couldn’t believe you’d be writing a book about humans and not chimps, and in the Goodness Paradox – but where does your brain wander now when you’re sitting in front of that fire staring into the flame, thinking about chimps, thinking about other great apes, thinking about us, what are the questions that are still unanswered in your brain? Where would you like to be looking and wondering?
Dr. Richard Wrangham:
Well, I mean there are sort of details of the stories that I’ve been working on for years. I think that among the chimpanzee species you’ve got or subspecies the western chimpanzees that live in Ivory coast, Sierra Leone, Liberia, there are fascinating indications that they have been self domesticated in ways. I’d love to see how the genes work out to be able to see if they really do go in a bonobo-like direction compared to other chimpanzees. So there are fun population differences among the different apes in Africa to be able to work out. I would love to be alive long enough to see the genetic data really worked out to see how similar humans are to domesticated animals in our genes. I would love to know why is it that in domesticated species and in females compared to males, you find less aggression in populations and sexes that have smaller brains?
Dr. Richard Wrangham:
I think that’s a really fun question that people haven’t really thought about much. But it’s world chimpanzee day and I would love to be able to think about conservation just very briefly because what I just love about the fact that I’m able to study chimps and think about what they mean is that it gives me an excuse to be with them. That pure aesthetic, intense enjoyment of spending time with this extraordinary creature in the forest. You’ve had it. We are privileged people to have done this. And the question in my mind, the big question is how long will this go on? We don’t know of recent populations of or recent species of great ape that have gone extinct. I think the last big one I think was the famous gigantopithecus, the largest great ape ever known, which went extinct just about the time that Homo sapiens evolved. Maybe there was a connection, but about 300,000 years ago in China.
Dr. Richard Wrangham:
But Darwin said that it’s impossible that the great apes would be able to survive as the human population increases and needs its food and converts so much of the wild habitats into farming areas. He said all the great apes will go extinct. Well he was writing in the 1870s for that one. So here we are 150 years later and they’re not thriving exactly and their populations have gone down, but nevertheless there are reasonably good big areas where people are dedicated to conserving them. So if I’m thinking about a big question for the future, my question is are we gonna be able to keep them alive? Because boy, it’s worth doing. I mean this has been an incredibly exciting period of discovery over the last 50 years. I just happened to have coincided with the time when Jane Goodall, the first person to do a long-term fuel study of chimpanzees immediately following George Shaler and Diane Fosse starting the studies of great apes of gorillas.
Dr. Richard Wrangham:
This is what a wonderful time to be alive and be interested in natural history because for the first time in the history of the human species, we actually understand what our neighbors, our neighboring species are like instead of just having myths about them, we really know. And it’s at the same time as we’re getting an understanding of evolutionary biology, that means that we can explain what we see as well as understanding and describing it. So it’s enormously exciting. We are so privileged as a species to happen to have chimpanzees, bonobos, gorillas and orangutans, four species of great ape alive with us that give clues to what kind of species we are, where we came from. Cause I mean if we were a Steeler calf, if we were that great big deep sea fish off the Madagascan coast, we wouldn’t have any close relatives. We wouldn’t know.
Dr. Richard Wrangham:
We couldn’t speculate about how it had all worked and our cosmology would be so unscientific and confused. But as it is, we are getting a picture of really these big questions of where did we come from? And it’s because the great apes are alive still. If they died like so many primates did a thousand years ago in Madagascar, when people arrived there, then we’d be so impoverished. So for me, the big question is can we find ways to balance the needs of growing human populations with the opportunity to keep significant populations of the great apes alive in the different subspecies that may be different from each other? Because that is a really important legacy to bequeath future generations.
Gerry Ellis:
You mentioned privilege a couple of times. It has has been a privilege to see these animals in the wild and I do feel that commitment, I have said more than once, that it would be one of the most tragic things that I would ever do is to walk into a fourth or fifth grade classroom and try to explain to children what a great ape was, not what it is. Richard, this has been a privilege. Thank you so very much for taking the time to be with us on Talking Apes. I really encourage people who are listening to this, if you haven’t picked up any of the books, start with Catching Fire. It’s an amazing read. It is all the things we’ve been talking about, but it really does sort of flip that energy consuming brain of yours around and it makes you think about the world and our species in a different way. Again, thank you so much for being on the podcast today. Really appreciate it.
Dr. Richard Wrangham:
Oh, real pleasure.
Gerry Ellis:
I’m enormously grateful to Richard for joining us on World Chimpanzee Day and exploring the past few million years of us becoming Us. I’m also thankful for his final thoughts on the importance of ensuring chimpanzees and all great apes remain with us on this journey into the future. You’ve been listening to Talking Apes. For each episode, we explore the world of apes with experts from research to outreach with passionate primate people and conservationists from around the world. Our guests are at the forefront of news about our wild primate cousins. You can find previous episodes of Talking Apes on our website at www.GLOBIO.org/talkingapes or wherever you get your podcasts.
