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LYNN NEARY, host:

It's MORNING EDITION from NPR News. I'm Lynn Neary.

STEVE INSKEEP, host.

And I'm Steve Inskeep.

Next time you see an asparagus floating in a bathtub, as we all occasionally do, you will instantly think of Charles Darwin's theory of evolution. Because, as we're about to hear, floating asparagus contributed to Darwin's theory. This true story can now be told by NPR's Robert Krulwich.

ROBERT KRULWICH: A hundred and fifty years ago, when people asked how come you can go to Australia and there are kangaroos hopping, hopping around everywhere - but you go to places that look almost exactly the same, say on grasslands in Africa - and there are no kangaroos?

Now, why is that? Why don't the same kinds of places have the same kinds of animals? Well 150 years ago, there was an answer. It was simple one, says science writer David Quammen.

Mr. DAVID QUAMMEN (Science Author): God has made kangaroos and put them in Australia.

KRULWICH: So God did it. He decided?

Mr. QUAMMEN: That was what He wanted to do. God created every species individually and put them down wherever they are. And actually I call that special creation plus special delivery.

KRULWICH: So that was the explanation. Even among some of the most learned people around. But then, says Quammen…

Mr. QUAMMEN: Darwin came along and said wait a minute, I don't think that's the explanation. I think these things all evolved from common ancestors.

KRULWICH: So the reason you find kangaroos only in Australia and New Guinea, he said, it's not God's doing - it's because the earliest kangaroo ancestors evolved there and then they spread out but they couldn't get across the water that surrounds Australia. They went about as far as they could go. Every plant, every animal that you see, Darwin proposed, got where it is today, on its own.

Mr. QUAMMEN: Animals and plants must disburse. They must be capable of disbursing in order to explain what we see on the planet by way of evolution.

KRULWICH: So it was critical to Darwin's theory to show how living things got to where they are today. And this can get kind of tricky. For example, cabbages - you can find cabbage plants on islands near Antarctica. Now, how would a cabbage get there?

Mr. QUAMMEN: Well, either God put it there, or it got there on its own.

KRULWICH: Yeah, but how does a cabbage seed cross an ocean on its own?

Mr. QUAMMEN: Yeah. How?

KRULWICH: Well it turns out that Darwin obsessed about this question: vegetable voyaging. For years, he concocted experiments and experiments that were so delightful and so unlike what you'd imagine…

Mr. QUAMMEN: Exactly, exactly. You remember the old TV show Watch Mr. Wizard?

KRULWICH: Yeah.

Mr. QUAMMEN: That was Darwin. That was Charles Darwin.

KRULWICH: Here's a perfect example. Darwin wondered: how might a radish travel?

(Soundbite of ocean)

KRULWICH: Well he imagined that a radish might accidentally get swept to sea on a windy day. But now, do radishes float?

Well Darwin had his butler, Mr. Parslow(ph) pour saltwater - kind of like ocean water - into a tub, and into that tub they plopped radishes. And carrots, and rhubarb, and celery. Mr. Parslow was - he was one of these proper English butlers?

Mr. QUAMMEN: Absolutely, yeah.

KRULWICH: I guess there aren't too many other butlers in the vicinity who happen to do this sort of thing?

Mr. QUAMMEN: Probably not. No.

KRULWICH: But Mr. Parslow also dropped in seeds …

(Soundbite of plopping)

Mr. QUAMMEN: He tried cabbage seeds, radish seeds, pepper, cress - as in water cress.

KRULWICH: And then they watched to see what floated, for how long and then they'd remove the wet seeds and they'd plant them to see if they would still grow. Some did better than others. With radish seeds?

Mr. QUAMMEN: He got 42 days worth of floating.

KRULWICH: And with cress?

Mr. QUAMMEN: Uh, 42 days plus a wonderful quantity of mucous, Darwin said, if I recall correctly.

KRULWICH: So it's stinky but it's in there.

Mr. QUAMMEN: Yeah, a slimy mess that still travels the ocean.

KRULWICH: And …

Mr. QUAMMEN: And that's typical of Darwin that he would not say, you know, a disgusting or a gross quantity of mucous. He would say a wonderful quantity of mucous, because everything about the natural world was wondrous to this guy.

KRULWICH: Okay, so that's 42 days for the radish, 42 days for the cress, how much now for dried asparagus seed?

Mr. QUAMMEN: Eighty-five days, they stayed afloat.

KRULWICH: Eight-five days.

Mr. QUAMMEN: And then he took them out and planted the seeds and they germinated.

(Soundbite of ticking clock)

KRULWICH: So let's do the math, Darwin did. If an asparagus seed can float for 85 continuous days and an ocean current moves roughly 38 miles a day. Let's multiply 85 times 38 - that means an asparagus can sail 3,230 miles across the sea. That's, that's like Magellan. Asparagus is king.

Mr. QUAMMEN: Well, at least among those Darwin looked at. Yeah.

KRULWICH: So yes, ocean crossing vegetables are possible.

But Darwin didn't stop there. One day, his eight-year-old son Francis said to him, you know, dad, did birds float, kind of like ships? And his father said, yeah.

Mr. QUAMMEN: He seems to have been a terrific father.

KRULWICH: So Francis said, well why don't we feed a bird some seeds, so that the seeds get inside the bird, and then, you know…

(Soundbite of a gunshot)

…shoot the bird? And then, you know, plop it in the tub, the corpse, and let it float for awhile?

Mr. QUAMMEN: So he suggested that, and Darwin said, you bet, Francis. That's a great idea.

KRULWICH: Then after a month or whatever, they opened up the dead carcass, and they pulled out the seeds inside, and they planted them.

Mr. QUAMMEN: And found that those seeds also germinated.

KRULWICH: Thereby establishing the principle that seeds can either float on their own or they can hitch a ride.

Mr. QUAMMEN: As passengers inside a bird, as passengers attached to the foot of a bird…

KRULWICH: Which then led Darwin back to animals and to the last science article he ever published, in which he proposed the possibility of flying clams. Now, at this point, Darwin wasn't so well.

QUAMMEN: He's suffering from degenerative heart disease, but he's still working. he's still very much alive, mentally.

KRULWICH: And one day he gets a letter from a shoe salesman, a young guy named Walter Crick. Now the way this story goes, you imagine Crick out in the woods collecting beetles when he just happened to see, it was a water beetle, and when he got down he looked real close…

QUAMMEN: And attached to one of the legs was a little clam. A little freshwater clam.

KRULWICH: A very little clam.

QUAMMEN: Yeah, very little. Small enough that the beetle scarcely noticed it.

KRULWICH: And Crick thought, hmmm…

QUAMMEN: That's kind of curious.

KRULWICH: So he wrote Darwin. And he said, you know, I think you might be interested in this, and sure enough Darwin wrote right back and he asked him all kinds of questions that Crick couldn't answer, because after all, he was in the shoe business.

QUAMMEN: So he did something better than, you know, fake it. He sent the beetle with the shell attached to Darwin. He mailed it.

KRULWICH: He just popped it into an envelope?

QUAMMEN: He popped it into an envelope, said…

KRULWICH: Was the clam still attached to the beetle?

QUAMMEN: It was. It was.

KRULWICH: So he says, okay, well you take a look for yourself?

QUAMMEN: Yeah.

KRULWICH: So a day or two later, the beetle and the clam did arrive at Darwin's house in an envelope. But they were separated now. And the beetle?

QUAMMEN: The beetle was dying by the time that he got there.

KRULWICH: It wasn't feeling very well.

QUAMMEN: It wasn't feeling very well.

KRULWICH: But right away, Darwin could see a possibility here.

QUAMMEN: This is very interesting. This goes back to the whole subject of dispersal, of how creatures can travel from one place to another.

KRULWICH: Maybe this little clam can fly from…

QUAMMEN: Aha!

KRULWICH: …place to place.

QUAMMEN: Right. Because this beetle is a swimming beetle, but it can also fly.

KRULWICH: So maybe clams can fly from pond to pond, hitchhiking on a beetle. Darwin couldn't prove this because he felt kind of badly watching that little beetle he had suffer.

QUAMMEN: So this is why I mentioned it at the end of my book, because it's such a wonderful example of the kind of fellow this guy, Charles Darwin, was. He writes back to W.D. Crick and says, Dear Mr. Crick…

KRULWICH: As the wretched beetle is still feebly alive, I've put it in a bottle with chopped laurel leaves. Now he knew that those leaves give off a gas that would very gently help this beetle die.

QUAMMEN: And one of the very last acts of his life, he decided that he needed to put this beetle out of its misery. And then a few weeks after that, Darwin died himself.

KRULWICH: There is a postscript to this story. It turns out that years and years later, the shoe salesman, Walter Crick, has some grandchildren. And one of Walter's grandsons just happens to be…

QUAMMEN: Francis Crick, the co...

KRULWICH: Not the Francis Crick?

QUAMMEN: The Francis Crick, co-discoverer of the structure of DNA with James Watson.

KRULWICH: So, perhaps the greatest champion of evolution in the 20th century, who deciphered the structure and the code of DNA both, that guy's grandpa…

QUAMMEN: His grandpa was a pen-pal sharing beetle specimens with Darwin.

KRULWICH: And how strange and wonderful is that?

David Quammen's new biography of Darwin is called, The Reluctant Mr. Darwin. I'm Robert Krulwich, NPR News, in New York.

(Soundbite of music)

INSKEEP: And one read an excerpt about that, from that book, here on the Web. It's about a kiwi. You can find it at npr.org.

It's MORNING EDITION from NPR News.

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