Historian Asks, 'What On Earth Evolved?'

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The history of Earth features a few extremely successful species, such as ants, black pepper, sheep, and of course, humans. In his book, What On Earth Evolved, Christopher Lloyd explores their stories before and after man.

NEAL CONAN, Host:

This is TALK OF THE NATION. I'm Neal Conan in Washington.

2009 marks 150 years since the publication of Charles Darwin's "Origin of Species." And as our small part of that celebration, we present an award show. It's worth considering those species who have managed to change the world from the earliest organisms that squiggled about in the sea to the magnificently sophisticated creatures that managed to invent radio.

Presenting the awards, historian Christopher Lloyd, who for his new book took on the modest assignment of life, specifically the 100 most important species. And we'll give you two quick examples. Stony corals, tiny co-operative fish that constructed reefs that became islands, mountains and habitat for thousands of other creatures, they come in at number seven. And one spot ahead at number six is man.

So, give us a call if you'd like to know the evolutionary standing of a particular species. And we have an email challenge for you. What do you think made the top three, the most important species in the history of the Earth? No cheating. Step away from the Internet except for your email and send us your answer, talk@npr.org is the address. Our phone number, 800-989-8255. And you can join the conversation on our Web site as well. That's at npr.org. Click on TALK OF THE NATION.

Later in the program, Robin Givhan of the Washington Post on Tiger Woods, sex and sexism. But first, Christopher Lloyd joins from the studios of the BBC in Tunbridge Wells. His new book is "What on Earth Evolved? 100 Species that Changed the World." And it's great pleasure to have you today on TALK OF THE NATION.

CHRISTOPHER LLOYD: Great to be here, Neal, thanks.

CONAN: And it's nice to know we're more important than stony corals.

LLOYD: Yeah, only just. I have to say, there's only two points in it, actually. But you're right, we just put them to the post.

CONAN: And how do you decide which species is more important comparative to another?

LLOYD: Well, to be honest I wanted to write about 100 different species of which humans were one, so that we could see where we fit in really with the rest of the natural world. And so that we don't always look at the past from a human perspective. And I thought as a bit of fun at the back, having written the biography as all these amazing different living things with their incredible stories, that I would take upon myself the challenge of ranking them in an order of impact of one to a hundred. And I chose five criteria. One is their impact on evolution, another is their impact on human history, another the impact on the environment, so the land, the sea, the sky. Then, how pervasive they are, their global reach. And finally, how long have they actually survived? How many millions of years?

CONAN: So, that a relatively recently arrival would get marked down, like man?

LLOYD: Well, that's right, actually. And, yeah, Homo Sapiens we do worst when it comes to longevity. So, you know, at about 160,000 years, compared with that shark that you mentioned at the start, the euphagy(ph) who may have been around for about 400 million years, we kind of don't do well on that score.

CONAN: ...on that score. So, even though they came in 38 compared to our six.

LLOYD: They did come in 38 but they are amazing survivor, sharks, it has to be said. So their story is truly awesome.

CONAN: And you've divided them rather neatly into 50 species that predate Homo Sapiens and 50, well, you talk about those first 50 as engaged in natural selection. The next 50 after man, artificial selection.

LLOYD: Yeah, funny enough, that's a little bit the way that Darwin approached it in his book "On the Origin of Species." He started off with artificial selection, actually, which he called domestication. And the way in which we have changed different species or those species have changed us and actually you can look at it both ways.

CONAN: Mm-hmm.

LLOYD: Over the last 10,000 since we started farming is absolutely remarkable. And this is something that really struck Darwin and he believed there were some selective pressures at work that may have been in place long before humans existed. And that really gave him the clue to come with the idea of natural selection, which is, of course, what dominates the first half of this particular study - the first 50 species that evolved in the wild.

CONAN: And it's interesting, you do engage in the discussion of did man domesticate grains or the other way around?

LLOYD: Yeah, it's really interesting actually, particularly when you look at things like narcotics, some things like that, things that have a stimulating effect on our minds. And one of the chapters is on those, and if you look at, you know, different parts of the world where different types of plants grow, you'll find different characteristics of human culture beginning to come out. For example, in the Western hemisphere, the traditional narcotics that grow are things like cocaine and stimulants like coffee. And in the Eastern hemisphere, you'll find that the traditional plants are opiates, which are much more relaxing. And you can find different attributes of human culture coming out. And you begin to wonder which actually - whether the tail is wagging the dog, see what I mean.

CONAN: Mm-hmm.

LLOYD: Are we reflections of the plants that grow in our neighborhoods rather than the house just being always in control?

CONAN: If you'd like to engage into the conversation: 800-989-8255. Email us talk@npr.org. Christopher Lloyd is our guest. His book, "What on Earth Evolved? 100 Species That Changed The World." And let's start with Ruth(ph). Ruth with us from Chattanooga.

RUTH: Yes, hello.

LLOYD: Hello, Ruth.

RUTH: You were asking what we thought one of the top three would be. And my guess would be stromatolites would be in the top three because they gave us oxygen in our atmosphere.

LLOYD: I have to say Ruth you are absolutely on the nail. So, I will be crowning you now in our award ceremony.

(SOUNDBITE OF LAUGHTER)

RUTH: Well, thank you.

LLOYD: I'm hugely, hugely impressed. Where did you say? Chattanooga. That must be a very special place.

RUTH: Well, I'm staying here taking care of my mother for a time. I actually live in Louisiana, but I grew up in Chattanooga.

LLOYD: Fantastic. Well, maybe one day I'll get there and then I'll be able to sort of give you a free copy of the book because you're absolutely right. They actually come at number three and the species is cyanobacteria, which are a type of bacteria that live, as you know, on these rocky structures called stromatolites. And they really began to colonize the earth about 2.8 billion years ago and were the first photosynthetic organisms. So they gave birth to our oxygenated atmosphere. And...

CONAN: And still a few left off the coast of Australia, much beloved by nature documentaries.

LLOYD: Yes, indeed. In Shark Bay and there are some of the them under the seas off Bermuda and various other places. But I mean, those billions of years ago, the whole world was peppered with these structures. And they - it's extraordinary to think that the early atmosphere on the Earth had no oxygen in it and that actually it was primitive forms of life that gave us the oxygen. How amazing is that when you think, you know, we think we're so special and important, but actually we depend on all these other living things and we really depend on those stromatolites, cyanobacteria. So thank you, Ruth, for pointing that out and you're absolutely there with number three.

RUTH: Thank you. I plan on getting this book. This sounds fascinating.

(SOUNDBITE OF LAUGHTER)

LLOYD: Well, I hope you enjoy it.

CONAN: Thanks very much, Ruth.

RUTH: Thank you.

CONAN: Bye, bye. Let's go next to, this is Vitus(ph). Vitus with us from Tucson.

VITUS: Hey, how are you?

CONAN: Very good.

LLOYD: Fine and well.

VITUS: I wanted to say that it occurs to me that perhaps the human race has been colonized by yeast, since we grow them to create alcohol in vast numbers...

CONAN: Well, it's interesting...

VITUS: ...we're really just their slave.

CONAN: We mentioned that man came in at six and the stony corals at seven and yeast comes in, I think, right in there.

LLOYD: You've got it, Vitus, absolutely, number eight. So, they're there in the top 10. And yeast have got a fascinating story to tell. I mean, they are amazingly powerful and influential in nature. But for human history, it's yeast of course who has given us the opportunity to create alcoholic drinks, but yeast also creates natural preservatives within fruit and yeast has colonized all areas of the world. Tiny microscopic fungus, but with a tremendously big impact. So, you're absolutely right. They're not in the top three, but they're in the top 10, so you're very close to the money, Vitus. Thank you.

VITUS: Well, thank you for writing the book. I'm going to get it.

CONAN: Okay.

LLOYD: All right.

CONAN: Thanks very much. It was interesting as you were going through those mind altering things in coca, as you would expect, opium - coca - cocoa rather, coffee and tea. But ergot comes in very strong.

LLOYD: Yeah. Look, it's a fascinating one because it's actually the base for a drug called LSD and was only discovered really that - in the 1940s by a chap called Albert Hoffman. And he accidentally synthesized LSD which is made out of ergot, which is a parasitic fungus that attacks rye. And he ingested some of it, just out of curiosity, and then he took a bike ride home and it was the most weird bike ride you'll ever, ever read about. You can read about it in "The Story of Ergot." But he did make it home, but only thanks to somebody who was with him. And then, of course, he describes in great detail in his diary the experience he had as a result.

So it's thought, actually, that ergot isn't - ergot poisoning is something that gave rise to dancing fever, even could have been responsible for the madness that's supposed to have gripped the Salem witches in those Salem witches trials, or even in medieval times in Europe, dancing fever, which broke out across Germany because of poisoned rye, parasitic ergot. And even right back in ancient Greece, some of the ceremonies the Greeks indulged in are thought to have been - their stupor was induced by ergot that was infecting the rye around, and they made drinks out of it.

So it has a really interesting, long history that predates the synthesis of LSD, but, of course, in the modern age has become to be really quite significant.

CONAN: Here's a tweet from triangleman, who answers our quiz. And he proposes for the top three: cockroaches, E. coli and fruit flies.

LLOYD: Well, that's very interesting. Fruit flies are absolutely there, in at number 15. So I think that's an excellent guess. Fruit flies are incredibly great survivors and have been really, really very important in our understanding of genetics and diseases, because many of the genes in a fruit fly are very similar to the genes in humans. And the way that fruit flies are able to breed and so on has allowed scientists to understand how genetics work in a way they never would have done without fruit flies. And, of course, they spread diseases with their legs because they crawl over dung and then they fly elsewhere, and so they've been a very great impact.

E. coli actually isn't in the list. I think it's in one of my 30 species that nearly made it. I think its influence has been...

CONAN: Honorable mention, I think.

LLOYD: An honorable mention. Exactly. We've got to have that list, very important. But it's a very recent kind of - recently come onto the radar, I think, in terms of, certainly, human perception.

And the other one the gentlemen mentioned was...

CONAN: Cockroaches.

LLOYD: Cockroaches. Well, they belong to the kind of beetle family, and I had to - a bit of a dilemma when it came to beetles because you probably know they are amongst the most diverse living things, and there are hundreds of thousands, millions of species of beetles. And I had to choose one, and I actually chose the dung beetle, which has an amazing history going back to ancient Egypt, where they were venerated as being a reflection of the gods because they would roll up balls of dung. And they sort of represented the passage of the sun over the course of a day and then the dying of the sun at night, which, when it went to the underworld, as it were.

And so on Egyptian hieroglyphics, you find these dung beetles, but they have an incredible ecological role to play because they really regenerate the soil. They sort of plant their eggs inside the dung, and they use that dung in a very kind of sustainable way, really. So a tremendous amount of agriculture that we depend on and the fertility of the soil is down to the work of dung beetles and other organisms.

But cockroaches, I know in the States, there's a - is a big thing. Over in the U.K. here, we tend to be more paranoid about spiders than we are about cockroaches. So there may be a cultural reason why it isn't in the list, OK. So...

CONAN: I recommend you rent an apartment in the city of New York and then come back to me in a couple of years.

LLOYD: Yeah, exactly. I've heard the stories already, but you're right.

CONAN: We're talking with Christopher Lloyd. His book is "What On Earth Evolved?" It's a tour of the 100 species who managed to claw their way up the evolutionary ladder. We're taking your calls at 800-989-8255. Email us: talk@npr.org. We've identified one of the top three: cyanobacteria. Two more left to go. Well, let's get the drum roll ready. I'm Neal Conan. Stay with us. It's the TALK OF THE NATION from NPR News.

(SOUNDBITE OF MUSIC)

CONAN: This is TALK OF THE NATION. I'm Neal Conan, in Washington. In the evolutionary game, it's hard not to think of humans as the cream of the crop. Well, we're number six in Christopher Lloyd's book "What On Earth Evolved." The bacteria that live in our gut, lactobacillus, rank higher in terms of longevity and global reach.

He's talking with us today about the range of species that have survived and evolved, some splendidly, since the dawn of time, and 100 have really changed history. Fifty before man he's chosen, 50 after man. That's everything from the terrifying, sea scorpions and slime mold, to the delicious, like coffee and grapes.

Give us a call if you'd like to know which - if you think you know the top three. We've identified one of them, cyanobacteria - 800-989-8255. Email us: talk@npr.org.

And let's see if we can get another caller in. This is Nema(ph), Nema calling from San Francisco.

NEMA: Hey, how you doing?

CONAN: Good. Go ahead, please.

NEMA: Good. Well, I actually have to say I think one, at least one of the two have to be insects. I know...

CONAN: Oh no, no, no, no, no, no. You're trying to categorize. Is it bigger than a bread box is your next question.

(SOUNDBITE OF LAUGHTER)

NEMA: But I actually took a - I used to be a biology major, and I remember they were talking about the influence of certain inspects because they were able to fly, and they were able to...

CONAN: I'm afraid we're going to need a little more specificity than that.

NEMA: More specificity. Dang. I guess I really don't have - I guess I want to say maybe group hymenoptera.

(SOUNDBITE OF LAUGHTER)

CONAN: Hymenoptera. All right.

NEMA: Yeah.

CONAN: I'm not sure what hymenoptera are, but Christopher Lloyd, do you know?

LLOYD: I'm not exactly sure. You know, you tell us, Nema, what do you mean exactly?

NEMA: I think they're a classification of ants, so to speak.

LLOYD: Ah, right. Well, ants, that's great, because that puts it into everyday language for all of us. And ants are certainly there in the list, Nema, but they're not there in the top three. Let's just see if we - Neal, you can find ants as quickly as I can. Let's see where it is.

CONAN: Okay, well, they're - ant is number 25.

LLOYD: Thank you very much. There we are, number 25. And so Nema, that is a very good comment. I mean, ants have colonized the world. They have changed ecosystems. They are incredibly sophisticated, with models of society. In fact, you can find almost every type of human society in an ants nest. You've got soldier ants. You've got worker ants. You've got slaves. You've got kings and queens. You know, you've got so many different things that evolved probably 100 to 120 million years ago, all there represented in the natural world, which is why it's so fascinating to connect human history with natural history because we can learn so much about ourselves.

So ants are absolutely in there, a really good suggestion, and thanks for the call, Nema.

CONAN: Appreciate it.

NEMA: All right. Thank you.

CONAN: And here's an email from Rick in Laramie, who suggests rhizobium, the N-fixing bacteria, he says, and also the ever-worthy wine grape.

LLOYD: Well, and this is Nick, is that right?

CONAN: Rick.

LLOYD: Sorry, Rick. Well, I am incredibly impressed, Rick. You are - you know, you have got our number four. So rhizobia comes in at number four, and that is a terrific guess because I often give lectures and things about this way of looking at natural and human history, and seldom do people come up with rhizobia. But you're absolutely right.

This is a type of bacteria that fertilizes the soil, and it lives in a sort of symbiotic relationship with legumes - that is, clover and beans and other things. And it depends on those legumes because the legumes feed it sugars from their photosynthesis, but in return, the rhizobia fix the nitrogen from the air, turn it into fertilizer and fertilize the plants.

So they live absolutely in lock-step with each other, and the rhizobia fertilize the soil, and that's absolutely vital for other plants and for all living things, ultimately, in the food chain.

So rhizobia go right to the top of the list, number four - excellent, excellent guess.

CONAN: And he also guessed the grape, which does awfully well, too.

LLOYD: Yeah, the grape does awfully well, too. Let's have a look. The grape - I'm flicking through my list here...

CONAN: I'm flipping through, too.

LLOYD: ...seeing if we can - number 73, rate for the grape. I mean, it's got a fantastic story, but it's really only risen to particular prominence, I guess, since about 500 B.C. or so.

CONAN: Well, we're mostly talking about the repeal of prohibition in this country, but...

LLOYD: Yeah, sure, OK. Well, I take that all back, of course.

(SOUNDBITE OF LAUGHTER)

CONAN: Okay, let's go next to Jonathan, Jonathan with us from Homer in Alaska.

JONATHAN: Yeah, hi. I've got a few guesses here, but just to give you a glimpse of why we might make number six, got so interesting in the book, listening here, I asked my girlfriend to iPhoned it on Amazon, and it's already in the mail and on the way to Alaska here already. So...

LLOYD: Terrific. Well, I hope you enjoy it, Jonathan, thanks for your support.

JONATHAN: Oh, it sounds great. This is fantastic. Thanks for writing the book.

LLOYD: It was such fun to write.

JONATHAN: Oh, good. Well, so, the top three - I think - I've got to give my girlfriend credit for this one, but the pollinators. Bees have got to be up there pretty high, and then I like corn because we're reading Michael Pollan's book.

CONAN: Well, we all like corn.

JONATHAN: And then I want to know where viruses fit in there, probably bubonic plague or something like that.

CONAN: Well, according to his book, right at the beginning.

JONATHAN: Oh, yeah. Viruses begin the whole story, you know. And there's this increasing hypothesis that life on Earth was begun by genetic replicators that were the ancestors of today's viruses, the RNA world. So I give them really kind of pride of place in the story of life on Earth, and each group of species I've prefaced with a narrative. So you can read about the story of life on Earth right from the beginning, from the first replicators, which may have been ancestors of viruses, right through to the present day, as well as look at the biographies of all the species.

But your girlfriend has come up with some terrific suggestions, and I'm very happy to say that everything she suggested is very much in the list of the 100.

So bees come in at 33, and that's only just a little bit ahead of corn, which we have a habit of calling maize over here. But that comes in at number 35. And viruses, well, the top virus in the list is number nine, and that is influenza.

Now, that may not come as too much of a surprise, but influenza has had a dramatic effect on human history. Some of you may know that the Spanish flu, at the end of the first world war in 1918, actually killed twice as many people as soldiers that died in World War I.

CONAN: Just on that same list, though, we have an email from Jeff in Riverside that says - Riverside, Missouri: Is penicillin on the list?

LLOYD: It is, and that is number 10, Jeff. So this is great. We've got some terrific suggestions. We all seem to be on the right wavelength, which is great. So it comes in at number 10. I mean, it's had a meteoric impact, I should say, since the 1940s, when it was introduced during World War II. Before that, penicillin, you know, has been very successful, but didn't have much of an impact on human history.

But, of course, in the last 50, 60, 70 years, penicillin has transformed the prospects of humanity, and in some ways is responsible - or for a great part - is responsible for the growth of populations from two or three billion back in 1940 to approaching seven billion today. So that's a huge deal.

CONAN: Jonathan, thanks very much for the call.

JONATHAN: Thank you.

LLOYD: Thanks, Jonathan. And thank your girlfriend.

CONAN: And let's go next to Matthew, Matthew with us from Summit Lake in Wisconsin.

MATTHEW: Yeah, hi, there, gentlemen.

LLOYD: Hi, Matthew.

MATTHEW: How's everything going today? I think that the author gave me an idea when he was talking about soil fertility with the dung beetle. I'd have to think that the earthworm would be very important in the evolution.

LLOYD: My goodness, and who are we talking to, Neal? This is...

CONAN: Matthew.

LLOYD: Matthew, you - where's the drum roll? Have we got the drum roll and the cymbals? That's it. Well done, Neal, excellent. Ba-doom! You've got it, Matthew. Absolutely. At number one in the 100 species is the earthworm.

MATTHEW: Hey, how about that? OK.

LLOYD: So, well, that is brilliant. Thank you very much.

MATTHEW: I'd also like to give out a shout out to the ginkgo.

(SOUNDBITE OF LAUGHTER)

LLOYD: Steady on, one thing at a time.

CONAN: There you go.

LLOYD: So the earthworm gets the number one spot.

CONAN: But why the humble earthworm?

LLOYD: Well, you know, earthworms, there are a lot of reasons, but the ancestors of today's earthworms evolved about 600 million years ago at the bottom of the sea. And they evolved in a way, the template for all animal body designs - and I know this is going to sound a little bizarre, but in many ways, humans are a kind of elaborate form of earthworm - or worm, at least.

If you think about it, we eat our food through our mouths. It goes through a hole in our bodies, comes out the other end, and we have a three-layer system for our body design where the organs press between our guts and our skin and then this outer layer of skin. And this is exactly the same template as worms have, and they are the kind of pioneers of animal body design. So they really get a big tick in the impact on evolution.

They then survived spectacularly well through five mass-extinction events. And one of them, 252 million years ago, wiped out, you know, 96 percent of marine species and 75 percent of land species but didn't touch the earthworm because they bury in the ground. They're not fussy about what they eat. And generally speaking, when life gets tough, it's great to be small, and it's great to be able to hide. Earthworms do that.

And then when it comes to human history, you know, there could have been no human civilizations without earthworms because they ventilate the soil, they fertilize the soil, because the excrement kind of provides all the right ingredients for soil fertility, and even things like the Egyptian pyramids, they wouldn't have been built without earthworms.

And I know that sounds really odd, but, you know, it was only thanks to the earthworms plowing up the soil when the farmers - so the farmers could leave their fields and then go and build the pyramids for the pharaohs over three months while the earthworms got on with the plowing.

And funnily enough, the earthworm happened to be Charles Darwin's kind of favorite species. He wrote his last book all about earthworms, and it was amazing to see it come out top of the list because literally, I did all the scoring and I pressed it all in my spreadsheet, and there it was, the earthworm, yeah.

CONAN: Number one. All right. We should mentioned an emailer named Jonathan also got worms. He also mentioned another species: horses.

LLOYD: Horses. Yeah, well, horses absolutely are on the list. And I tell you that the story of the horse and how it's become so successful in a world of sort of seven billion humans is absolutely fascinating. But the horse comes at number 58. And I was surprised in a way it didn't come a little higher, because if you think about it, the horse and humans have had such a shared destiny. You know, we take horses into war with us. We - horses have plowed our fields. They provided transport, and so on.

But on some of the other criteria, they don't score quite as highly. They have, you know, horses are already domesticated perhaps four or 5,000, 6,000 years ago, compared with something like an elephant. Elephants have got much more longevity. They also possibly have a greater ecological impact. And elephants are the only lumberjacks of the natural world, and they can clear forests to create light so that forests can renew themselves. And their dung provides the seeds around which termites build their nests.

And these are impacts that are really important but don't belong horses. So by having a kind of balance of different criteria, you create some quite interesting kind of orderings in the rankings. So elephants actually come a little higher than horses. But horses are there, and they're really significant.

CONAN: And speaking of forests, there is a species of which I had never heard called lepidodendron...

LLOYD: Yeah.

CONAN: ...which is - I perhaps put in Irish. But I'm sure it's got an apostrophe there after the O. But anyway, this was a species of tree which vanished a long time ago, and only flowered at the very top and once in its life.

LLOYD: That's absolutely right. And to think about it, actually, bamboos only flower once in their life. So it is a sort of ancient habit of some plants. But the lepidodendron tree was amazingly successful. It was the first really, really successful tree that evolved about 320, 350 million years ago. And it would - there were like giant telegraph polls. So they would shoot up incredibly quickly in a race to try and get to a light.

And because they didn't have any branches or leaves on their trunks, but only at the top, they could grow incredibly densely. So they're the most densely packed forests. And then therefore when they die, they would fall over and they'd all fall over on top of each other and they'd never properly rot because there were layers and layers of these trees in the forests and the air could never really get to them.

So as the sediment built up and as the forests were flooded, as the seas rose and things, all these deposits of these trees got pressed and mashed up in the geological process of the earth, and have become for us the most valuable commodity, really, over the last 200 or 300 years to man, and that is coal. So most of the coal deposits, the best coal deposits, actually, are the ancient remains of lepidodendron trees.

CONAN: So think about West Virginia or Kentucky or parts of Wyoming covered...

LLOYD: You've got it.

CONAN: ...in all these trees.

LLOYD: Absolutely.

CONAN: We're talking with Christopher Lloyd. His new book "What on Earth Evolved?: 100 Species That Changed the World." You're listening to TALK OF THE NATION from NPR News.

And let's go to Ed, Ed with us from Traverse City in Michigan. Hi, Ed.

ED: Good morning - good afternoon, gentlemen.

CONAN: Hi, Ed.

LLOYD: I would like to weigh or guess perhaps ocean's buffet of plankton or indoor algae.

LLOYD: Well, Ed, that is terrific. You know, we've got the number one spot that was sorted out, and number three, and you have seem to zoomed in on number two.

CONAN: Congratulations there, Ed.

LLOYD: So I'm absolutely - the quality of your listeners, Neal, is really awesome. I'm incredibly impressed. And algae...

CONAN: TALK OF THE NATION listeners come in at number 14.

LLOYD: They probably - yeah, we may be given, I have to give them an honorary place, wont' we, in the table? You're absolutely right. Number 14. So you've just knocked the mosquito out now.

CONAN: And a good thing, too. You've swat it right out of there.

LLOYD: Oh, yeah, and a good thing. You got it. We've swatted it away. And now NPR listeners. So algae come in at number two. Very ancient organisms dominate the ecosystem in the sea, but - and on water, responsible for emitting a gas called dimethyl sulfide, which is vital for cloud formation.

And thanks to the ability for water vapor to condense around the particles of dimethyl sulfide, we get more and more clouds than we would have done. And that has allowed the earth to become much cooler because it reflects the sun rays away from the ground. And therefore, even though the sun's temperature has risen by 25 percent over the period of life on earth, the actual temperature the earth has dropped dramatically, making conditions for life on earth much, much more favorable.

CONAN: Mm-hmm.

LLOYD: And we have to thank algae for that. The other thing is that there's a tremendous potential for algae in the future to be able to be farmed in a way that procreates biofuels in a sustainable basis, to absorb carbon dioxide, turn it into biofuels, and that would be an ideal material for being able to power aircraft in the future. And there's a lot of research going on over in Boeing and so on to try and find algae - ways of farming algae in order to power transportation in the next hundred years.

So it'll be an interesting one to watch. Maybe we'll that number one.

CONAN: Ed, thanks very much for the call.

LLOYD: Sure. I have a quick question for us before we cut off?

CONAN: If you make it very quick.

LLOYD: What affected the red tide when I was kid growing up in Newport, Rhode Island? Red tide would come in. Was that dead algae or an algae plum?

LLOYD: Yeah, probably was an algae plum, actually. I mean, there are red algae and there are green algae and there are brown algae. So there are various different types. So my guess is it would have been one - probably the red algae, yeah.

CONAN: All right, Ed.

OK: OK. Thank you.

CONAN: Thanks very much for the call. And it's interesting. Algae, of course, are a non-flowering plant. But you come to the conclusion that on your list, though we've not talked about all that many flowering plants, that they are, in fact - they make up quite a number of the nominees.

LLOYD: They do, Neal. Actually, I was surprised at the end when I counted it all up - 32 out of the 100 species that changed the world are flowering plants. And they evolved, the first flowering plants may be about 180 million years ago, but they've had such a dramatic impact on people. That's what's one of the most amazing things, because we, you know, we depend, of course, on plants. But flowering plants have so many ingenious ways of pollinating, of fruiting, of intoxicating, of poisoning.

You know, so you look through everything from the things we're familiar with, like corn or rice or coco or - chocolate, rather - and coffee and tea and roses and lotus flowers. They're all flowering plants and they're amazingly well - and others that evolved before humans, like the durian fruit, which is a huge fruit that evolved in the age of dinosaurs. It's probably the smelliest thing living on the planet, you know, and bamboo and all sorts of other things.

It's just incredible, the variety and the utility to which flowering plants are put, so they've - their impact has been truly immense.

CONAN: Well, thank you so much for your time today. We appreciate it.

LLOYD: It's a real pleasure, Neal. Thank you.

CONAN: Christopher Lloyd is the author of the book "What on Earth Evolved?: 100 Species that Changed the World," with us today from the studios of the BBC at Tunbridge Wells. If you'd like to read more about the evolutionary marvel the earthworm, you can read an excerpt about it at our Web site. Just go to npr.org and click on TALK OF THE NATION.

LLOYD: If you think Tiger Woods has been dragged through the tabloid mud, Robin Givhan says that's nothing compared with the women whose names have been linked with his. She joins us next. Stay with us. I'm Neal Conan. It's the TALK OF THE NATION from NPR News.

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Excerpt: 'What On Earth Evolved?'

Cover of 'What On Earth Evolved?'

Earthworm

Family: Lumbricidae

Species: Lumbricus terestris

Rank: 1

Subterranean wrigglers whose constant burrowing fertilizes the soil.

ACCORDING TO CHARLES DARWIN, no living thing has had such a profound impact on history as has the earthworm. So fascinated was he by these humble creatures that he devoted an entire book, published in 1881, to the formation of soil (then called 'vegetable mould') through the action of worms:

'The plough is one of the most ancient and most valuable of man's inventions; but long before it existed, the land was in fact regularly ploughed, and still continues to be thus ploughed, by earthworms. It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.'

Few people have ever spent as much time analysing the behaviour of earthworms as Darwin. Towards the end of his life, playing with worms became something of an obsession. He blew various musical instruments at them to see if they would react to sound, concluding that: 'worms do not possess any sense of hearing. They took not the least notice of the shrill notes from a metal whistle, which was repeatedly sounded near them; nor did they of the deepest and loudest tones of a bassoon.'

He put them on his grand-piano to see how they would respond to the vibrations of its hammers hitting the strings:

'When the pots containing two worms which had remained quite indifferent to the sound of the piano were placed on this instrument, and the note C in the bass clef was struck, both instantly retreated into their burrows. After a time they emerged, and when G above the line in the treble clef was struck they again retreated.'

Finally, he wanted to find out if these small, slimy creatures could think intelligently for themselves. His experiment involved cutting out 303 elongated paper triangles and coating them with fat to stop them shrivelling up from the morning dew. After sprinkling the leaflike triangles on the grass outside his living room window, Darwin withdrew overnight to see how the worms responded. In the morning he recorded that 62 per cent of the time the worms tackled the triangle's apex, the easiest way to manoeuvre the material cleanly, before dragging them into their burrows. 'We may therefore infer, ' he wrote, 'that worms are able by some means to judge which is the best end by which to draw triangles of paper into their burrows.'

Whether these experiments tell us more about Darwin than worms is a moot point. They absolutely reveal a man with an insatiable passion for creative tinkering. His life was blessed with no financial worries (Darwin's family was well off and his wife came from the wealthy Wedgwood ceramics family) affording him the luxury of unlimited time at his disposal. He used it to write his books, correspond with other naturalists around the world and design intricate (and sometimes rather eccentric) experiments to probe the inner workings of nature through the observation of species. Bees, beetles, barnacles and pigeons fell under his critical gaze but, as his last book on vegetable mould demonstrates, no creatures fascinated him quite so much as nature's perennial ploughs.

Earthworms are annelids, a phylum of creatures whose evolutionary past stretches back at least to the Cambrian Explosion c. 530 million years ago when the trilobites first developed sight and marine creatures evolved bones and shells. Burgessochaeta is an ancestral, twenty-segmented sea worm whose fossils were found by Charles Walcott in the Burgess Shale (see page 60). Descendants of these marine creatures came ashore at the time of the first invertebrate invasions of the land, c. 450 million years ago, making their living in damp soils broken up by bacteria, fungi and the roots of colonizing plants. These earthworms have been ploughing up the earth, ventilating the soil and nourishing

terrestrial ecosystems with their excrement ever since. Five mass extinctions have occurred over the last 500 million years, some of which devastated up to 96 per cent of all species, but none of them ever touched these creatures. Slice a worm in half and it re-grows as if nothing happened. Divide one half and the same thing happens. One worm even survived forty such butcherings, all in the name of science.

The effects of worms on human history are as profound as they are unwritten. French scientist-cum-poet Andre Voisin was one of the few experts who properly highlighted the role of worms in the birth of ancient human civlizations. Were it not for their continuous regeneration of soils around damp river valleys such as the Nile, Indus and Euphrates, early agricultural societies in Egypt, India and Mesopotamia could never have succeeded in building humanity's first large-scale

urban communities. Even the Egyptian pyramids, said Voisin, were built thanks to the nourishment of the soil by earthworms. It was only because of their hard-work that farmers could take time off from toiling the soil themselves to work as a labour force for their pharaoh's ambitious building projects.

Throughout human history earthworms have unintentionally but undeniably triggered the rise of civilizations. Wherever earthworms plough, people thrive. When worms perish, societies collapse. Infertile soils led to the demise of the people of ancient Sumeria. Rising levels of salt as a result of irrigating the land with sea water killed off the worms around the mouth of the Euphrates river and the soil turned sour. By 2000 BC their civilization was so weak from lack of food that they fell easy prey to Assyrian invaders from the north.

It might be easy to think that worms matter little today, replaced by artificial fertilizers and pesticides that guarantee soil fertility anywhere and everywhere they are spread. But no. Once again it was largely thanks to the earthworm that the unsustainable nature of using such methods was originally exposed.

Rachel Carson was a teacher and environmental campaigner of the 1950s and 1960s. She is famous for warning that Americans might one day wake up to discover they could no longer here the birds singing in the trees. The reason, she said, was that artificial pesticides, such as DDT, were poisoning the soil. While robust earthworms are able to tolerate such toxins, for those creatures that eat them it was a different story. As few as eleven worms that had ingested DDT are enough to poison a robin — either killing it or making it sterile. Since robins regularly eat up to twelve worms an hour the use of DTT put their populations, along with similar birds, at risk of annihilation.

The prospect was terrifying enough to have DDT banned in the USA by popular demand (although it is still used in some African countries, such as Kenya, to support the global cut-flower trade — see rose, page 341). Carson's book Silent Spring (first published in 1962) inspired the founding of the US Environmental Protection Agency in 1970. Therefore, the robust digestive system of the earthworms is, in a curious way, inextricably linked to the birth of the modern environmental movement.

But which worm species has had most impact? There are some 15,000 species of segmented worms in the annelid phylum, including leeches, and marine polychaetes — as well as earthworms. They range from the now rare but enormous purple-headed Giant Gippsland (Megascolides australis), a native Australian worm that grows up to three metres long, to the extremely common red wrigglers (Eisenia foetida), vermicultural alchemists that turn kitchen vegetable scraps into rich garden compost.

Lumbricus terrestris, the European earthworm, is now probably the most prolific and invasive species in the world. Its success is largely thanks to the spread of Europeans from c. 1600 onwards. Immigrant farmers inadvertently brought these earthworms, sometimes called 'night-crawlers', to the Americas in everything from the soil in their potted plants and their horses' hooves, to the treads of their boots and the wheels of their wagons. Today, there is hardly a region of North America where Europe's earthworms have not made a home for themselves. There they continue to plough, ventilate and fertilize the soil to the general benefit of life in and on the Earth.

But their presence is not always welcome. Artificially introduced invasive species almost always have a darker story to tell (see also eucalyptus, page 264 and rabbit, page 330). Native American redwood forests that were once free of worms are now being invaded by this European species. It is now relentlessly munching its way through carpets of fallen leaves — a vital habitat for native American insects, amphibians and ground-dwelling birds. Without leaf litter on the soil's surface, the seedlings on which the future of these forests depends will not germinate. Within a generation or two, some experts fear that those forests not already mined by man may instead be undermined by the worms he has introduced.

Darwin's fascination with these ubiquitous, noiseless digesters of the Earth was well placed, confirming their rank as our Number One species (see table on page 390). Whatever they lack in glamour, colour or a sense of adventure (most worms move only about fifty metres in their four-year lifetime) they make up for in their constant ploughing, harrowing, fertilizing and recycling of that most precious of all the planet's assets — the living Earth itself.

Copyright © 2009 by Christopher Lloyd. Reprinted by Permission of Bloomsbury USA.

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