Ask An Expert: An Evolution Education

IRA FLATOW: This is Science Friday. I’m Ira Flatow. We’re heading back into the classroom for the rest of the hour, a bit of biology 101. Most of us were taught about evolution in science class growing up. But how much do you actually remember? And what questions do you have now that you were afraid to ask the teacher back then?

Well, my next guest has written a whole book about the science of evolution, how it has changed everything from bacteria to humans. So it’s time for you, our listeners, to ask an expert about evolution. There are no stupid questions, only questions that don’t get asked. Our number– 844-724-8255, 844-SCI-TALK. Or you can tweet us @SciFri. Let me introduce my guest Dr. Prosanta Chakrabarty, author of Explaining Life Through Evolution, which will be out next week on August. 8

He’s also the curator of fishes at Louisiana State University in Baton Rouge. I don’t think we’ve ever had a curator of fishes on the program before. Welcome to Science Friday. Welcome back.

PROSANTA CHAKRABARTY: Thanks. Thanks, Ira. It’s great to be on the show with you.

IRA FLATOW: It’s nice to have you. Let’s start by talking about what inspired you to write this book because I know you live in Louisiana, a state where anti-evolution science education is law. Was that partly what inspired you?

PROSANTA CHAKRABARTY: Yeah, absolutely. That was probably the first thing that got me putting pen to paper was these anti-evolution laws that were passed by the legislature, from Bobby Jindal era. And they’re still there.

IRA FLATOW: Yeah. Is this an American phenomenon, the question of evolution and how to teach it?

PROSANTA CHAKRABARTY: It’s not just American, but it is sort of uniquely something special about– some countries, for sure. So India just stopped teaching evolution at the K through 12 level. Turkey recently stopped, basically banned teaching evolution as well. But the way we teach it and the way we’ve dealt with it in the United States as state by state has been pretty unique.

IRA FLATOW: You have found– and you mentioned this in the book, because I can relate to this. You talk about that some people have a fixed mindset about something. Let’s say they don’t believe in evolution. There’s virtually nothing you can do about it.

No amount of data will change their minds. They have a belief system of what you call mistrust. And as I say, we have found that here, talking with people on this program. Tell us about what you have found.

PROSANTA CHAKRABARTY: Yeah. And that’s always been my goal is not to convince somebody of one thing or the other, just to explain that evolution is how we understand and explain the origins and diversity of life. And this is how scientists understand it. This is how I understand it.

And I can’t make somebody’s belief system collapse in a way that they need to see the science of evolution the same way I do. So I don’t go out to change their mind, just to get them to understand. And hopefully, that might start a little crack in their understanding to get them to think about science a little bit differently. So to gain trust first, I think, is the most important thing before they start to understand what you do and how you understand it.

IRA FLATOW: Gaining trust is a hard thing.

PROSANTA CHAKRABARTY: Yeah. It sure is.

IRA FLATOW: Very hard. There is a famous mural– I think we’ve all seen it– called “The March of Progress,” depicting evolution as a progression from monkey to Chimp and then to a hunched caveman, leading directly to modern man. You show it in your book, and you say this image has done more harm than good trying to better explain evolution to people. Why do you say that?

PROSANTA CHAKRABARTY: Yeah. It’s an interesting figure that’s usually the shorthand people use when they say evolution. And it shows this progression from what we expect to be lesser beings to us. And so it looks like evolution is goal oriented, which it is not. It looks like we’re the top of the pinnacle of evolution, which we’re not.

There is no pinnacle. There is no goal. It’s much more of a fanning out from that origins of life into the diversity of life we see today. So an amoeba or a cardinal that we see today is also the descendants of that first life, and it wasn’t leading to us. Monkeys aren’t evolving into us. We are apes. We have common ancestry.

IRA FLATOW: Common ancestry.

PROSANTA CHAKRABARTY: It’s very different.

IRA FLATOW: Yeah.

PROSANTA CHAKRABARTY: Yeah.

IRA FLATOW: How do we know that evolution is real? Let’s get that right out of the way quickly.

PROSANTA CHAKRABARTY: Sure. For me, the best evidence is we can look at what we call the tree of life, this connection of relationships between all life on Earth, through the DNA that we can examine, and compare, and study. And we can put fossils on that tree of life, so we can place where we’re fossils that we find almost every day fit within that 3.5 billion years of life on Earth. So for me, the evidence of evolution is all around us.

It’s in our body. We don’t have a perfect body. In fact, we have many what I’d call flaws or not perfectly fit elements, including our backs and knees. So for me, the evidence is everywhere.

IRA FLATOW: Well, we have some– I said that I’m going to give my listeners a chance to ask everything they wanted to know, and they have so many questions. So let’s go right to them. Matt in Rome, Georgia.

PROSANTA CHAKRABARTY: Let’s do it.

IRA FLATOW: Hi. Welcome to Science Friday. Hi, Matt. Are you there?

MATT: Hello.

IRA FLATOW: Hey, there.

MATT: Yes, Ira. Hi, how are you?

IRA FLATOW: Hey, how are you?

MATT: Great.

IRA FLATOW: Go ahead.

MATT: So I love reading about human evolution, and I find it interesting to read about Neanderthal populations that lived alongside Homo sapien populations. And then from my understanding, we’re considered two different species, but then I also read that we were mixing with the two populations and we even carry Neanderthal genes with us today.

So my question is, how do we know that they were two different populations? And if so, how can we have Neanderthal genes in us?

IRA FLATOW: Yeah, great question. Great question. What do you say about that, Prosanta?

PROSANTA CHAKRABARTY: Yeah, it is, indeed, a great question, Matt. So in part, they’re our closest living relatives are chimpanzees, but our closest relatives that we know about in the history of time were Neanderthals. So we are Homo sapiens, and they were Homo neanderthalis. And there are, in fact, many people in the US, people of European descent, that have about 2% of their genome has Neanderthal in it.

And how does that happen? Well, we have not one or two Neanderthal ancestors but maybe many. That’s how you can have those remnants of another species DNA in our own genome. So there was a bit of, let’s say, hybridization going on between our species. There’s also some controversy about whether Neanderthals were, in fact, a different species. Perhaps we were so close that they don’t deserve to be in their own distinct species, and there might be a subspecies of Homo sapiens. But for now, I think most people are going with them being separate but that there was quite a bit of hybridization maybe 25,000 years ago or so in Europe.

IRA FLATOW: Matt, does that answer your question?

MATT: That’s great. Thank you so much.

IRA FLATOW: Thank you. You’re welcome. All right, let’s stay with the flow here. Let’s go to Fred in Bellingham, Washington. Hi, Fred. Let me make sure I got you on the air. Welcome to Science Friday. Oh, I may have– let me try Fred there. Fred, Hi, welcome to Science Friday.

FRED: Am I on?

IRA FLATOW: Yes, you’re on.

FRED: All right. I’ve been wondering for some time, whether life has emerged more than once on Earth. Is there a unique evolutionary line?

IRA FLATOW: Wow. Deep thoughts today on the show.

PROSANTA CHAKRABARTY: I wonder that same thing. So we know that we can connect all life on Earth living today to a single common ancestor. However, life probably had many spurts and starts and maybe some missed falls before that. So we can trace the earliest life on Earth from fossils to about 3.5 billion years ago, but maybe in the time between the origin of the Earth, about a billion years before that and that 3.5 billion years, there were multiple origins and what we see today is who survived that from that one common ancestor.

So it would be great to know. We just don’t know. We know that life evolved at least once but perhaps more than once even before that.

IRA FLATOW: Cool. We have a comment, a question, from Twitter. When does the line get crossed from a new species? Jake and Little Rock wants to know.

PROSANTA CHAKRABARTY: Yeah. That’s a case by case basis. So if we look at populations that are diverging, if they are close together, if they don’t have a geographic barrier, sometimes that can take a very long time. Other times, there are species, like ferns, that can duplicate the number of chromosomes they have, and in an instant, they are a new species essentially.

So it just depends. It depends on the group, and how reproduction happens, and how much hybridization, like we talked about in Neanderthals and humans– and Homo sapiens, so it depends. And it’s not always something that everybody agrees on.

IRA FLATOW: Right. Right. Well, speaking of agreeing on, has our understanding of evolution evolved, let’s say, since Darwin’s On the Origin of Species?

PROSANTA CHAKRABARTY: Sure. Absolutely, yeah. Darwin, the great evolutionary mind, didn’t know about genetics, and he didn’t know about hormones. And he didn’t know about many of the things that we use to study evolution today. So a large part of what he explained was natural selection and adaptation, but he couldn’t explain neutral evolution, which is genetic drift and the other mechanisms that we know and understand today about how species change and evolve over time.

IRA FLATOW: How much in common do we humans, we modern humans, have with, let’s say, algae, bacteria, single cell organisms?

PROSANTA CHAKRABARTY: For me, that’s one of the most amazing things about us, in particular, and the life on Earth that we see today is how much of our genes are shared. So I think there’s something like a 60% of our genes that we have– and we only have about 20,000, 25,000 genes– are found in things like banana. There’s so much shared genes, genes that we got from viruses and bacteria. There’s so much crossover. And so onions and strawberries have more DNA than us. And how that makes us us and how it makes them that is just the marvel of life. And so there’s a lot of cover.

IRA FLATOW: I learned that this– last week, I was up in Maine at the Schoodic Institute, and I had a great time with those folks up there. And I was watching what they call rockweed, which is the seaweed that grows on all those rocks in Maine. And a scientist was telling me that people don’t know that seaweed is not a plant. It’s an algae, and, in fact, because it is an algae it’s closer genetically to humans than it is to plants. And I thought that just blew my mind.

PROSANTA CHAKRABARTY: And mushrooms. Mushrooms are close. [INAUDIBLE] the whole tree. It’s an unbelievable, and it’s amazing.

IRA FLATOW: It is because you say in your book that nothing in biology makes sense except in the light of evolution, and that’s sort of what you’re talking about.

PROSANTA CHAKRABARTY: Yeah. If you attribute that quote to me, every evolutionary biologist is going to roll their eyes, but I’ll take it. It’s from Theodosius Dobzhansky. And yes, it’s true, though. Every time I think about any part of biology, if we don’t think about how we’ve changed, and transformed over time, and how life has moved us to where we are, it’s very difficult to explain without evolution.

IRA FLATOW: Let’s go to the phones before we go to the break. Let’s go to Chris in Cleveland. Hi, Chris.

CHRIS: Hey, Ira. How are you all doing?

IRA FLATOW: Hi, nice to have you. You got a question for us?

CHRIS: Yes, sir. I do. I just have a quick question, and maybe you guys can just answer it for me. How come so many smart scientists believe in evolution? Question mark scenarios as to how man actually came about– Australopithecus, Piltdown Man, Neanderthal, Cro-Magnon, but yet none of them referred to anything in the Bible, especially in the beginning of Genesis, where it talks about where mankind came from. And I’m quite certain that God didn’t create us to be swinging from trees or walking around as apes. So do you have an actual answer to that?

IRA FLATOW: Good question.

CHRIS: And why seems to be so complicated but when we go to Revelation– I’m sorry, Genesis, the answer is right there?

IRA FLATOW: OK, good question Let’s see if we can get an answer. What do you have to say about that, Prasanta?

PROSANTA CHAKRABARTY: Sure. And people have their understanding of how our origins came from, and some have a biblical view. And I don’t want to change anybody’s minds about that. And we could stop studying everything if we just believe in our religious texts and leave it at that.

And so in Genesis, if you follow the Genesis version, you can accept that but also have a scientific curiosity, which many scientists hold both religious beliefs and scientific ones. And so our origins can both be something that includes the 3.5 billion years of our understanding of how life has changed over time and includes us being mammals, and being apes, and being vertebrates. And also if they want to believe an origin that includes a creator, I have no qualms with that, and many scientists don’t.

We don’t need to have pick or choose one or the other. I think it’s best to let people believe how they want to believe but also understand how the scientists understand their own work.

IRA FLATOW: And Chris, I hope that answers your question.

CHRIS: Thank you, gentlemen, very much.

IRA FLATOW: You’re welcome.

PROSANTA CHAKRABARTY: Thank you.

IRA FLATOW: Our number– 844-724-8255. This is Science Friday from WNYC Studios, talking about evolution. When did you, Dr. Chakrabarty, get interested in this?

PROSANTA CHAKRABARTY: Yeah. I always loved animals. I’m a New York City kid. And I grew up and go to the Bronx Zoo and the American Museum of Natural History, and look up at the dinosaurs, and wonder where they went and where they came from. And that led me down a the slippery slope where I am now to studying evolution at Louisiana State University.

IRA FLATOW: And you’re a little– as you said at the beginning, you’re upset that the evolution can’t be taught the way you think it should be in schools.

PROSANTA CHAKRABARTY: Yeah. And I fear that it’s going to be worse there’s some legislation that may come down throughout the United States that may change how we study. The separation of church and state is definitely being challenged. And I think that’s unfortunate, and I think science should be taught in the science classroom and nothing else. And any other intrusions of non-scientific thought will muddy our understanding, and so it should just be science being taught.

IRA FLATOW: Quick question from Joe in Orlando. Hi, Joe. Joe, are you there?

JOE: Hello?

IRA FLATOW: Yes.

JOE: Hi, there. I just had a real quick question for you. I say the extent of my education and evolution went back in high school in Florida, where it’s watching Inherit the Wind and the Scopes Trial. So forgive me. That’s all I got.

IRA FLATOW: Quickly.

JOE: We see apes now in the zoo. Will they become humans at one point down the line?

IRA FLATOW: OK.

JOE: Give them a [INAUDIBLE].

IRA FLATOW: OK.

PROSANTA CHAKRABARTY: No, they won’t. Like we talked about the depiction of primates turning into humans today, that’s not how evolution works. We share common ancestry, but things alive today are not turning into humans. Their evolution is progressive, but everything is moving in its own direction and not necessarily towards a goal.

IRA FLATOW: So there was one point in common ancestry that there was a branching off instead of a following after. Would that be–

PROSANTA CHAKRABARTY: Exactly.

IRA FLATOW: So different animals branched off, and chimpanzees did not become humans. They just branched off into– and they had a common ancestor.

[MUSIC PLAYING]

Dr. Chakrabarty, do you find it difficult to explain evolution to people?

PROSANTA CHAKRABARTY: I don’t. I try to think about my own understanding and how I came to learn and appreciate how beautiful the ideas are of evolution. And so I like sharing it, and it moved me to write this book. And I hope people like it and understand it in a way that I do now. And I hope that works.

IRA FLATOW: Let’s go to the phones. Elijah in Cleveland. Hi, Elijah. Hey, there. Can you hear me, Elijah?

ELIJAH: Hello

IRA FLATOW: Yes.

ELIJAH: Yes. OK, cool. Thank you so much for having me. OK, so my question is we’re talking about chimpanzees or apes evolving into humans. There’s a very popular video out there that you may have seen where AI predicted what human evolution is going to be in which it goes from ape to man really quickly, and then it goes from man to machine. And then it goes from machine to just a symbiotic all you see at the end of it are tubes, and pipes, and wires. There aren’t even robots anymore to where it just seemed like it would be a symbiotic collective of what the human mind created–

IRA FLATOW: How did they eat?

ELIJAH: –and the whole world–

[LAUGHTER]

–the whole world would be nothing but wires, and tubes, and is AI going to benefit the planet kind of thing?

IRA FLATOW: Yeah, OK. I get your drift. I get the drift. Let me get a– thank you for calling, Elijah. Let me get a comment.

PROSANTA CHAKRABARTY: Sure. I’ll stick with organic evolution, how we understand our own bodies changing. And there’s a great book by Scott Solomon about future humans, and he goes into that a little bit.

I’ll say that the beginning of that question started with we turned from chimpanzees into humans. And again, that’s not how it works. We share common ancestry.

IRA FLATOW: Yeah. Not– excuse me– not only as we talk about anti-evolution Crusaders being in many states, but many states have been dealing with anti-LGBTQ bills. And you argue in your book that variations in sex, and gender, and sexuality can all be explained by evolution. Tell us about that.

PROSANTA CHAKRABARTY: Sure. And I’ll just start by saying, first, you don’t need an evolutionary biologist to tell you that the spectrum and diversity of life includes this. The spectrum of genders, and sexes, and sexualities– we can be nice to people and accept people for who they are without an evolutionary biologist telling us.

But there is this– we know across the diversity of life of the species we know that there are different genders. There’s different sexes in species. Not everything is male or female. There’s many intersex people. There are lots of ways that we can explain gender that are dealing with hormones and not necessarily something that matches your chromosomes or what’s in your pants.

And so our understanding of human sexuality and genders is different than our understanding of how we test and study life on Earth. But it’s something that I think people often are asking, why do we have people who aren’t part of the reproductive group of people, when they think about evolution? And so for me, it’s better for people to have an understanding of this diversity of genders and sexualities and be accepting of it and not use evolution as some way to discredit how people live their lives.

IRA FLATOW: You have an example that might be a little shocking to our listeners who are fans of the movie the movie Finding Nemo about how some fish have evolved, clownfish, in particular.

PROSANTA CHAKRABARTY: Yeah. Clownfish are sequentially hermaphroditic. So they all start off as males, and then the biggest one becomes the big dominant female and bears the next generation. So if you remember the opening scene of Finding Nemo, when Nemo’s mother gets eaten, what would happen was, the– Marlin, the larger clownfish surviving would become the large female. Perhaps then another individual, male, maybe Nemo himself would start a new family that way.

And there are some strange things happening in the animal Kingdom, for sure, or we would consider it strange from our human perspective. And we don’t have anything like that in humans. But there are plenty of examples of this non-binary roles of sex in the animal kingdom.

IRA FLATOW: Let’s go to Rebecca in Pensacola, Florida. Hi, Rebecca. Welcome to the program.

REBECCA: Oh, thank you.

IRA FLATOW: Hi, go ahead.

REBECCA: I am a teacher, and I was just wondering how your expert, whose name I do not know because I tuned in a little party to the program, could explain how I could explain to children– like, for example, in our elementary curriculum, we talk about giraffes and how they evolved to have the longer necks so that they could reach the food at the taller branches. And that’s explained to children.

But then they proceed to ask other questions. And I’m trying to figure out how we can dumb it down without having them go home and say, Miss So-and-so was teaching me that what I learned at church is not true. And I did hear the caller who called in about Genesis, and I completely understand that. But I’m trying to dumb it down for children without getting super, super duper technical but without causing parents to call the front office and say that we’re not doing the right thing.

IRA FLATOW: So how you can teach it without saying the word evolution in it?

REBECCA: No, no, I don’t– well, and I hate to say that because the curriculum has the word evolution. And the standards do teach– well, and it’s more probably adaptations, like animal adaptations and how their adaptations have evolved over time in order to help them adapt to their environment, and survive, and survival of the fittest, and all of that.

So yeah, I guess I’m just trying to figure out a way so that when they– kids are inquisitive and curious, and they want to know more, especially if this is something they haven’t been taught. So I’m trying to figure out a way to dumb it down for children.

IRA FLATOW: OK. Let me just tell you. You’re talking to Prosanta Chakrabarty, who wrote the book Explaining Life Through Evolution. I know you tuned in late, and that’s who you’re talking to. I just wanted to be polite on that. Yes, Prosanta. Do you have a suggestion?

PROSANTA CHAKRABARTY: I do, and I think actually the caller did a great job at explaining evolution there. When I’m talking to children, I like to couch it in terms of competition, at least the adaptation, natural selection part. And so I like to think of there being many individuals being born, and j can talk to the kids about their siblings and how they compete for resources, even within the house.

And so if they want to have the most cookies or if they want to gain access to something, being taller may allow them to do that compared to their sibling. And so I get them thinking about the giraffe, if you will. The taller giraffes being born of those offspring can survive by reaching the most leaves, the highest leaves, and those that don’t don’t make it and may perish.

And it’s a bit of a dark competition story, but not everything can survive. Not everything that is born can survive. And so those that are best fit, that have those adaptations to survive in that environment, do so. And those that don’t don’t. And so those that live move on to make the next generation with those adaptations. So I usually try to put it in terms of siblings and other classmates, if you will, in terms of competition.

IRA FLATOW: I hope that helps, Rebecca.

REBECCA: Yes, it does. I can envision the children picking the shortest kid in the room and saying, you’re out.

[LAUGHTER]

But–

PROSANTA CHAKRABARTY: Yeah. And then make sure the shortest kid knows that he can reach some stuff maybe the tallest kid can’t. So it might work both ways.

REBECCA: Gotcha. OK, well, thank you for that.

IRA FLATOW: You’re welcome. Thank you for calling. Yeah, a lot of people have– especially teachers have challenges to face.

PROSANTA CHAKRABARTY: I think so, and I hope this book helps them a little bit. It’s meant for a general reader, so hopefully, some school teachers can glean some stuff out of there for their classroom.

IRA FLATOW: All right. Let’s see how many more questions we can get in. Let’s go to Nathan in Springfield, Missouri. Hi, Nathan. Nathan, are you there?

NATHAN: Yes.

IRA FLATOW: Hi, go ahead.

NATHAN: Yeah. I’m actually going to switch my question up a little bit just because I think we’ve already answered the one that I had initially. With the science of epigenetics and all of the new research that’s coming out, historically, I’ve always been taught that evolution was based on random genetic mutations. However, whenever you take into account epigenetics and how much the environment really does sway those mutations, has that affected your research and when looking back, rolling back the timeline, and looking at some of these major mutations that have led to very, very successful species?

PROSANTA CHAKRABARTY: For me, epigenetics is especially important, not just for my work. But I have identical twins, so whenever I see–

IRA FLATOW: Could I interrupt and just–

PROSANTA CHAKRABARTY: Sure.

IRA FLATOW: –explain for our audience what epigenetics is?

PROSANTA CHAKRABARTY: Yeah. So epigenetics is many of the non-heritable changes that happen. So if somebody is a smoker, they may pass down to their next generation changes, environmentally induced differences. So it’s how your environment and DNA that interplay is epigenetics.

So it’s not just reading the DNA. It’s how the environment and your genes are working together to produce different proteins or to produce different behaviors, for instance. So it’s this cloud around your DNA that how it’s being read can be determined by the environment, in part.

And so epigenetics is extremely important. It explains like why, if I put one of my identicals growing up in middle-class American family versus one growing up maybe in a poor family in India, will look very different, just how their environment is impacting how their DNA is being read. But I would say the heritable changes are still largely genetic. And so although mutations can happen everywhere, the ones that are passed down in the egg and sperm are the ones that matter for heredity. But epigenetics is certainly something that we’re learning more and more about, and their power is incredible in transforming how we act and might explain a lot more than even we know right now.

IRA FLATOW: This is Science Friday from WNYC Studios, talking about evolution with Prosanta Chakrabarty, author of Explaining Life Through Evolution. We’ve talked about natural selection. What about unnatural selection? And I’m talking about here humans breeding domesticated animals to have certain traits. Are we playing a hand in evolution here?

PROSANTA CHAKRABARTY: Sure. Darwin starts actually Origin of Species with two kind of boring chapters on pigeons and domestic breeding of them because he wants to show that artificial selection, which people understand better– and that’s the breeding of different breeds of pigeons or dogs– is the same thing that’s happening in nature. But to your question of how are we impacting the world, well, we’re also not just using artificial selection from breeding, but we’ll start using CRISPR, these gene editing tools, and how that will change how evolution works. That’s a big open question that we’re still learning how we’re doing that now.

IRA FLATOW: Interesting question. A tweet coming in from Flavio– he says, how music became so important? Is it involved in evolution? Every community has it.

PROSANTA CHAKRABARTY: Yeah. For human evolution and questions like that, it seems like if we backtrack into what makes us successful, maybe what makes us successful versus species that lived with us, like the Neanderthals and Homo naledi and other species, maybe it is we survive because we had these communities. And maybe those communities had music and had a religious inclinations or some beliefs that they were shared that allowed us to survive when other human groups didn’t, other human species didn’t. And so yeah, that’s an interesting question.

It’s true everybody makes music. And everybody seems to enjoy music. Maybe that’s part of our evolution, but that’s a little bit beyond my scope of expertise there, too.

IRA FLATOW: Well, let’s talk about the limits of your scope of expertise. And not questioning how good you’re at it, but what do you want to know that you don’t know now? And what would it take to find that out?

PROSANTA CHAKRABARTY: Oh, the biggest question in evolutionary biology is about the origins of life. And we know life evolved and life has a common ancestor. But what happened in those steps where we go from maybe that was something that was very, very simple, a few protein-building amino acids to something that could self replicate– was it RNA? Was it something like a virus with ribosomes? Was it something extraterrestrial?

Those early origins of life on Earth, that’s the mystery of mysteries, as Darwin put it. That’s the real part that we’re trying to better understand. And we can reconstruct some things, but it happened a long time ago. And most of that memory is erased from the fossil record. So that’s still the biggest question and the one I’d love to know the answer to.

IRA FLATOW: The primordial soup you’re talking about. I guess, if you understand the primordial soup here, you might be able to understand it on some other planet, or moon, or something like that.

PROSANTA CHAKRABARTY: Yeah. I’m glad you said moon because that’s my bet, too. It’s something like some of Jupiter’s moons that have more water than we do.

IRA FLATOW: Yeah, yeah, you and Arthur C. Clark.

PROSANTA CHAKRABARTY: Yeah.

IRA FLATOW: Thanks for taking time to be with us today.

PROSANTA CHAKRABARTY: Great. Thanks for having me.

IRA FLATOW: Prosanta Chakrabarty, author of Explaining Life Through Evolution on sale next week. He’s curator of fishes at Louisiana State University in Baton Rouge. And if you want to read an excerpt from the book, head to our website sciencefriday.com/evolution.

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