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Defining Human Uniqueness In 'Almost Chimpanzee'

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Humans and chimpanzees share very similar genes — some analyses peg the differences at just 1 percent. But in his book Almost Chimpanzee, science writer Jon Cohen focuses on our differences, from the way we eat and communicate to our susceptibilities to disease and aging.


If you lined up our DNA with the DNA of our closest relative, the chimpanzee, you'd see remarkable similarities. But clearly, despite sharing all those same genes, we're not all that much like our jungle cousins.

They hoot and holler; we talk about philosophy or, this afternoon, about science. They spend all day roaming the forest gathering food and chewing it for hours; we throw our food in a microwave and cook it and eat it in seconds.

And chimps have a very different medical history, interestingly. They don't get the same cancers we do, they rarely get heart disease or arthritis, which are a common plague of humans.

What happened to our bodies and to our brains in the six million years since we began to diverge from one another that makes them chimps and us human? That's one of the questions in my next guest's new book, "Almost Chimpanzee." That's us, almost chimpanzee.

The book also looks at some of the people who dedicated their lives to researching the similarities and differences between humans and chimps, including crazy ones like one Russian scientist who, in the 1920s, tried the unthinkable: crossing a human with a chimpanzee, trying to create a humanzee.

Jon Cohen, our guest, is the author of "Almost Chimpanzee: Searching For What Makes Us Human, In Rainforests, Labs, Sanctuaries, and Zoos." He's also a correspondent for Science Magazine. He joins us from a studio in San Diego. Welcome back to SCIENCE FRIDAY, Jon.

Mr. JON COHEN (Author, "Almost Chimpanzee"; Correspondent, Science Magazine): Thanks so much, Paul.

RAEBURN: So what prompted you to go off on this journey around the world in search of chimpanzees and chimpanzee fanciers of various sorts?

Mr. COHEN: Well, it started because I have covered the HIV/AIDS epidemic for about 20 years, and there was a provocative paper, actually by a group here at U.C. San Diego, that suggested that there was an immunologic difference that explained why HIV in chimpanzees didn't seem to cause disease except for some very rare instances where they put a whole bunch of different viruses into one chimpanzee.

And then that just got me thinking, well, you know, that's a pretty profound difference. And what other differences exist? And the human genome had been sequenced, and the chimp genome in 2005 was sequenced. And I thought, well, I'm just going to dive in and see what the differences are that would surprise me. And I found tons.

RAEBURN: So we keep hearing that we share 99 percent of our genes with chimpanzees, and that's supposed to impress us somehow. I'm not sure because we're not much like chimpanzees. We're coming up on a break, but tell me a little bit about that 99 percent figure.

Mr. COHEN: Well, that refers to genes. And the human genome is mostly made up of DNA that does not code for proteins, which is the classical definition of genes. It's non-coding DNA.

If you look at the genes alone, yes, there is a 1.2 percent difference. But when you start looking away from genes and everything else, there's probably about a five percent difference.

RAEBURN: Okay, so let me just pause for just a moment. We'll be right back after this short break.

(Soundbite of music)

RAEBURN: I'm Paul Raeburn. This is SCIENCE FRIDAY from NPR.

(Soundbite of music)

RAEBURN: From NPR, this is SCIENCE FRIDAY, and I'm Paul Raeburn.

We're talking this hour about what makes us human and what makes chimps chimps with my guest Jon Cohen, the author of "Almost Chimpanzee: Searching For What Makes Us Human, In Rainforests, Labs, Sanctuaries, and Zoos." He's also a correspondent for Science Magazine.

So Jon, we were talking about the 99 percent of identical or nearly identical DNA between humans and chimps. And I guess what you found out is that what's important are some of the differences in what we casually dismiss as junk DNA.

Mr. COHEN: Yeah, and it's only been visible in the last decade or so. You weren't able to see this. The microscopes didn't exist, more or less.

And what you begin to see has really profound implications about what separates us from chimpanzees. I mean, yes, of course we're very close to chimpanzees. We're closer to chimpanzees and their cousins, the bonobos, than any other species. But science has redrawn the dividing line over the past decade that separates us.

RAEBURN: Okay, meaning what? Why have they redrawn that? What has happened?

Mr. COHEN: Well, when you had the two genomes to compare side by side, a research group out of Cambridge in Boston found that we may not have evolved the way that we thought. When the species separated, it looks now as though, or there's a strong argument that we separated, and then we mated with chimpanzees again for thousands of years. And then we finally separated.

That's a profound re-conception of what it means to be human, and...

RAEBURN: Yeah, this hybridization argument which I guess, I gather from your book, is still quite controversial.

Mr. COHEN: It is, and hybrids have always been pooh-poohed by evolutionary biologists. But I think there's a growing sentiment in evolutionary biology that hybrids can play a very important role in the development of a new species.

RAEBURN: So just to elaborate on that a bit, humans and chimps might have evolved as separate species at some point, but they were so closely enough related they could mate with one another, and then where does it go from there?

Mr. COHEN: Well, if you look at all of our chromosomes, the X-chromosome, it's a sex chromosome, is particularly odd because it's much younger than the others.

And so this research group said, well, why could it be what would make it younger? And their argument is that it was because of this hybridization event that, you know, I don't think anybody had ever discussed. I had never found any discussion of that ever before.

And, you know, if you're thinking about where do how do we become humans, what happened, what was the speciation event, you know, that's a grand question. And here's a completely new way to look at it.

RAEBURN: Now, speaking of hybridization, this Russian, Ivanov, who wanted to tell us a little bit about him and what he was trying to do.

Mr. COHEN: Well, he was a very prominent scientist back in the early 1900s. He was the world's leading artificial inseminator and had created several hybrids.

(Soundbite of laughter)

RAEBURN: There's a title, an achievement.

Mr. COHEN: You like that business card.

RAEBURN: Yeah, I like that, yeah.

(Soundbite of laughter)

Mr. COHEN: And he just and he made all these weird hybrids, zonkeys, like crossing zebras and donkeys and things like that, zorses.

And he just became enthralled with the idea of making a humanzee, and he eventually was able to go to Guinea in Africa, and he took some human sperm and injected it into three female chimpanzees.

And to his great disappointment, nothing happened, and when he came back to what was then the Soviet Union, he convinced the government to allow him to solicit a female human to be impregnated with the one ape that was old enough in the Soviet Union, was an orangutan named Tarzan. You can't make this stuff up.

RAEBURN: Yeah, you're not kidding.

(Soundbite of laughter)

Mr. COHEN: And so they were going - and this woman volunteered to be inseminated with Tarzan's sperm. Her life was meaningless, this would give her life great meaning. And Tarzan died before the experiment could happen. Then Ivanov was thrown in the Gulag, and he died a broken man.

RAEBURN: Tarzan died of excitement or anticipation, which I guess that's not recorded.

(Soundbite of laughter)

Mr. COHEN: I don't know what killed Tarzan, but I think Ivanov died of a broken heart.

RAEBURN: Right, right. So to move on to slightly more serious topics, one of the things I found was interesting in here, you know, you sit around, stories we've covered years ago and so forth. And one of those on my list has been: Whatever happened to those talking chimps and sign language and all of those things? And I was delighted to see that you'd looked into that to give us an update.

So tell us a little bit about that. I don't know, it must have been 20 years ago or so, maybe longer when there was a lot of excitement about this, and then it went away, yeah, even longer.

Mr. COHEN: Yeah, in the '60s and '70s was sort of the heyday of ape-language research. And there were many people who attempted to teach chimpanzees and bonobos and gorillas to speak using American Sign Language or symbols, plastic tokens or lexigram boards.

And the field kind of imploded upon itself in 1979 when a Columbia University researcher, Herbert Terrace, who had a chimpanzee named Nim Chimpsky, punning off of Noam Chomsky.

RAEBURN: The famous linguist, right.

Mr. COHEN: Linguist, and Noam Chomsky argues that language is innate, that there's almost an organ in our bodies for language.

RAEBURN: In humans.

Mr. COHEN: In humans, and so this researcher didn't believe Chomsky, so he named the chimp Nim Chimpsky. But then Herbert Terrace, when he reviewed his videotapes, what he thought looked like progress in teaching this chimpanzee sign language, he realized that they were taking cues from the humans and not really communicating the way he thought.

And then he reviewed other people's evidence, and he concluded that there was no evidence that anybody was making much progress at all. And the field kind of imploded from that moment.

There are still a few researchers who do this work, but it's also Steven Pinker, in his book "The Language Instinct," essentially ridiculed the field and I think raised a very important question: Why are we teaching them to speak our language rather than trying to understand how they communicate with each other?

RAEBURN: Now, did you talk to I couldn't quite tell from the book, but did you talk to Sue Savage-Rumbaugh, who was one of the pioneers in this area?

Mr. COHEN: No, but I did visit with her bonobos that she had trained and worked with, which are now at the Great Ape Trust in Des Moines, Iowa, and her sister, Liz Pugh, is their handler. And I met with her.

RAEBURN: Is Sue, is she still working there, and is she press-shy or...

Mr. COHEN: She's kind of semi-retired. I certainly attempted to speak with her. It wasn't for lack of trying.

RAEBURN: No, I don't bring it up to make that point that you missed something...

Mr. COHEN: Yea, no, no. It's fine.

RAEBURN: ...but I'm not surprised because she really took a beating, as I recall.

Mr. COHEN: She did, but I did speak with her bonobos.

RAEBURN: So you got it straight from the bonobos' mouth, so to speak.

Mr. COHEN: I got it straight. And it is a remarkable experience to speak with them. I mean, they have a computer touch-screen that has symbols on it called lexigrams, and I would say a word through a microphone, and they're in a little soundproof sort of booth, and they would...

RAEBURN: What did they tell you?

Mr. COHEN: Oh, they could select they showed me that they knew English words clearly. I mean, I could, there were maybe 300 symbols on the board, and I could say, you know, blueberry or ball or whatever, and they would select the proper symbol time and again.

What was but the flip side of that coin is, you know, there's a saying in science that if you have a talking dog, you don't need a control group. You know, if a dog just gets up and says hey Jon, how are you doing...

RAEBURN: You've got something.

Mr. COHEN: You've got something. They didn't do anything like that, and every time I tried to speak to one of them, Panbanisha, and ask pretty simple things like hey, do you like the yellow M&M better than the red one or whatever, there was no recognition.

And they said to me while I was there, if you came more frequently and they knew you better, if you weren't a male and all these explanations that may or may not be true, I don't know, but it just was impossible for me to have anything close to the sort of conversation I could have with most any three-year-old, four-year-old child - humans.

RAEBURN: I guess we should give up our efforts to get the bonobos on the show, then. It's not going to work.

(Soundbite of laughter)

Mr. COHEN: Well, it's going to be a strained you know, much of the literature on this is me-Tarzan-you-Jane sort of communication: Me want orange. Me want apple.

What the researchers contend in Iowa is that these bonobos are much better at receptivity than productivity: They understand a lot of what's said to them, even if they don't find the words to construct with sentences and grammar and the things that we consider to be language.

RAEBURN: It's interesting you should mention that because I have a 10-month-old at home now, and we're discovering every day that he understands much, much more. He can't really say more than a few words now, but he recognizes a lot of words that he hears, exactly the kind of thing you're talking about.

And in fact, you talked about some experiments where people tried to compare chimps and human infants. Tell us a little bit about those.

Mr. COHEN: Yeah, those are experiments done with these were called enculturated chimps, where they grew up in the home with a child in parallel to see how development worked. And some of this is really comical because they once again, they tried to make these chimpanzees speak English, and they would the humans would put their fingers on the lips of the chimp to make sounds or a tongue depressor on the tongue.

Their vocal apparatus is very different. It's hard for them to make the sounds that we make. Why would expect them to? And what became clear to the researchers doing this was that the human infant had a language, a vocabulary explosion at a very young age that never occurs with chimps.

But by the end of high school, we have about 60,000 words, the average human. And every chimpanzee, bonobo, gorilla, they all sort of hit the wall at two to 300 words, which is also where a dog hits the wall, or a parrot. So there's something really different about us. And it's not to say they don't communicate - of course they communicate. And of course they have communication that can say very specific, surprising things, but it's not language.

RAEBURN: Now, you talk about this fox gene - that's not quite the right name -what is it called?

Mr. COHEN: It's called FOXP2...

RAEBURN: FOXP2. Yeah, so what's - now, that is something that I gather is unique to humans and closely linked to our language ability.

Mr. COHEN: Well, the FOXP2 gene is in all species down to mice. It's just that what we learned in 2001 is that this family in England that has a speech disorder had a mutated version of this gene that was causing it to be inherited from generation to generation. Some people leapt upon this and said, oh, this is the language gene. Well, there's no such thing as a language gene, but certainly this was connected to a network of genes.

And the evidence is that this gene likely controls the muscles in the face and things that allow us to make sounds, and so then that impacts how we hear things and that impacts how we learn things. So it's kind of this cascade of events. But what they found when they compared the FOXP2 gene in humans to the one in chimps, that the human gene had a few mutations that weren't in chimps, and chimps basically were the same all the way back to mice. So that was a startling insight into a difference between us that no one had ever seen before. And since then, researchers have used that FOXP2 gene as a fishing hook to go into the genome and pull out other language-related genes. So that's the sort of redrawing of a dividing line that you couldn't have imagined even a decade ago.

RAEBURN: It's interesting - you mentioned some of these comparisons between chimps and dogs and so forth. We, you know, we immediately leap to the comparison between humans and chimps, but it's enlightening to look at some of these other - chimps are really more like some of these other animals that we wouldn't expect to have language ability, where we might think chimps would be capable of it.

Mr. COHEN: Yeah, there's this funny thing where there's kind of - when I talk to people about my book, and I've been doing this for four years. So I talk to a lot of people. And there's this kind of, duh, you know, of course we're different from chimps, but I'm intrigued by - look how many books have been written about the difference between men and women.

(Soundbite of laughter)

Mr. COHEN: Yes, of course, men and women are similar, but those differences are incredibly fascinating. And that's what driving - that was what drove my curiosity and still does, because I want to delineate. I want to find where exactly do we place that line.

RAEBURN: Now, one of the other things - the chimps get a very different array of diseases. They don't get heart disease or arthritis. What's - do researchers understand what's going on there, what explains that?

Mr. COHEN: Well, you know, this is a really under-researched area, but chimpanzees don't get Alzheimer's disease, it seems. They don't get most of the major cancers we get. Some of it is with viruses - it's a host-specific thing. So HIV in chimpanzees doesn't do much of anything, but they have their own version of HIV, their own chimpanzee AIDS virus that does appear to cause disease in them. So there are these subtle differences that can make huge differences in disease outcome. And the researchers who study this are hoping that if they can better understand why chimps don't get certain things, that we can then understand how we might be able to prevent them from harming humans.

RAEBURN: Give us a call if you have questions for Jon Cohen. The number is 800-989-8255. I'm Paul Raeburn. This is SCIENCE FRIDAY from NPR.

So another chapter - I hosted - I forget exactly when it was. But it was when Richard Wrangham's book on cooking came out.

Mr. COHEN: Yes.

RAEBURN: We had Wrangham on the show, who was great.

Mr. COHEN: I heard your interview.

RAEBURN: And you did - okay. So tell us a little bit about cooking and chimpanzees who are chewing and chomping all day and how that fits into this picture you've assembled.

Mr. COHEN: You know, when I first got to observe chimpanzees in the wild, I watched researchers do their work following chimpanzees around. It was astonishing to me that all they seemed to do all day long was eat and then take a nap and then eat and then take a nap and eat and take a nap. They have to consume a tremendous amount of food to stay alive, to stay healthy. And that's because everything's raw. What Richard Wrangham wrote in his book, "Cooking Fire" - not "Cooking Fire," I'm sorry. But in Richard Wrangham's book, he explains how cooking allows us to extract nutrients - "Catching Fire" - very quickly from, from plant material and animals that we eat. And there's a famous experiment that he cites in which rats are given a pellet and another group of rats is given the exact same pellet but pumped with air, and the ones that get - which is equivalent to cooking because it's easier to digest, and the ones that get the air-filled pellets become obese. It's the same exact thing.

RAEBURN: Same calories, same everything. It upends all our notions of these things.

Mr. COHEN: Yeah. So if you think about what fire does for humans, it allows us to let somebody go out and hunt all day and come home and actually eat dinner.

(Soundbite of laughter)

Mr. COHEN: There's time to get enough nutrients, and plus fire puts us around a campfire. Anyone who's been camping knows what you do around the campfire. You socialize.

RAEBURN: Yeah. And you...

Mr. COHEN: Humans are...

RAEBURN: You saw a bonobo build a fire. Tell us about that.

Mr. COHEN: I did, yeah.

RAEBURN: How did that...

Mr. COHEN: Yeah, well, Panbanisha was handed a box of matches and...

RAEBURN: This was the bonobo.

Mr. COHEN: The bonobo.

(Soundbite of laughter)


Mr. COHEN: And gathered some twigs and lit a little fire and roasted some marshmallows. You know...

RAEBURN: Did he or she offer you one? Or no such thing?

(Soundbite of laughter)

Mr. COHEN: No, he was not at all interested in sharing, but, you know, maybe she didn't know me well enough, but...


Mr. COHEN: But it was an astonishing thing to see. But, you know, if you look critically at that sort of behavior, yes, it is amazing that another animal would do this other than humans. But on the same hand, chimpanzees have been taught to ice-skate. They've been taught to knit.

RAEBURN: The circus - some of the early research was done by circus people who trained them...

Mr. COHEN: That's true. They were. They were trainers. They were animal handlers and trainers. And so I just look at all this stuff through a skeptical lens and say, well, okay, that's remarkable. But...

RAEBURN: But you know...

Mr. COHEN: it human?

RAEBURN: But there's something about those faces, isn't there?

(Soundbite of laughter)

Mr. COHEN: There is. They are very similar to us. And, you know, my book is called "Almost Chimpanzee," which is a pun off a 1925 book called "Almost Human." And there are two sides of the same coin. Yes, of course they are closer to us than any other species. But if you flip the coin over, they also hold the secret to why we are unique.

RAEBURN: That's a great place to stop, right there. Jon Cohen, thanks for being with us. Jon Cohen, our guest, is author of "Almost Chimpanzee: Searching for What Makes us Human, in Rainforest, Labs, Sanctuaries and Zoos." Thanks for your time, Jon.

Mr. COHEN: Thanks so much, Paul.

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