PW: You've succeeded at being a bestseller as a technical as well as a trade science writer, and in the introduction to your new book, I Have Landed, you say the boundary between the two is not as defined as it once was.

SJG: I've never seen them as different. I've pretty much seen them as the same thing. Good popular writing functions at the same conceptual depth as technical writing.

PW: You say in your book that this is your last.

SJG: It is, but for my Natural History series. I wrote 300 essays, and at some point I figured that the number 300 seemed like a good stopping point—quit while they still want you. After 20 years work, I'm delighted that I really got it done. It's been long in the planning and execution.

PW: Does your editor at Crown hope to get another one out of you?

SJG: No, not in this series. But there will be other books.

PW: For popular readers?

SJG: Sure, of course. I won't stop writing. That's what I do.

PW: How did you get into the trade business?

SJG: It was entirely accidental, as these things usually are. Out of the blue, I got a call one day from an editor of Natural History magazine. I guess I had some reputation for writing in this fairly literary style. He asked me if I wanted to write a monthly column for them. I found it interesting, and I found they actually pay you.

PW: When your first book in the series came out in 1977, did you expect that you—and evolution—would be a hit with the public?

SJG: No, I had no idea. But I think there has always been very strong interest in evolution. It's one of those topics that appeals to people.

PW: Evolutionary theory has held up pretty well under scrutiny since 1859 when Origin of Species came out, hasn't it?

SJG: Yes, but there are a fair number of major revisions that need to be made, which is scarcely surprising. Natural selection is not the only cause of adaptive change. Catastrophe, for example. The extinction of the dinosaurs was triggered by the impact of a large body on the earth.

PW: So you're confident the interest in Darwinism will last a while longer?

SJG: It's basically working out right. I don't think there is any other major theory that has held up so well for so long. Darwin's work really is a living presence.

PW: In your writing, though, you tend to be cautious about grand theories, don't you? You seem to derive great pleasure in overturning our basic assumptions.

SJG: I'd say that's a fair assessment. The world is very complicated. Most theories about it come out to be wrong. Grand syntheses rarely hold up in all their details. It's the basic spirit of any kind of scientific inquiry, skepticism. Most things turn out to be wrong, but some things turn out right.

PW: Are you surprised evolutionary debunkers continue to thrive in the so-called modern age?

SJG: I stopped being surprised by anything people believe ages ago. It's a big country. There's no other Western nation that has a creation movement like ours, so it is an American weirdness, to be sure.

PW: Do you get a lot of feedback from these people?

SJG: Some good, some bad. The bad is mostly people who send me their private 400-page theories of everything.

PW: How does such celebrity affect your day-to-day teaching schedule at Harvard?

SJG: As little as I can let it.