In Sea People (Harper, Mar.), Thompson examines how the peoples of Polynesia spread across the Pacific.

What was the impetus to write this book now?

I have gradually been working my way further and further back in time in my quest to understand the history of the Pacific. I started off in my last book with the end of the 18th century and the beginning of the 19th century, when Pacific islanders and Europeans who colonized most of the Pacific meet. I began thinking bigger about the history of the Pacific before Europeans got there.

What was the most difficult thing to write about?

The part that was the absolute hardest to work through—partly because there is such a shortage of secondary material—was the stuff on linguistics and mythology. That could be a book all by itself. I had to cut a lot of stuff that I was really interested in, but just couldn’t shoehorn in. The archaeology piece was fairly new to me, but I had a whole lot of help, in a sense, from other writers; I spent so many years just reading other people and having conversations in my head with them. It was really kind of wonderful.

What remaining questions about the Polynesian diaspora are most interesting to you?

I think that there are things that are interesting but are undiscoverable—how many voyages there were where people just disappeared in their attempts to find new islands, whether Polynesians reached South America, what actually happened at Easter Island. There’s stuff that we’ll never know about those early, early voyages of discovery.

What’s the main thing that you hope readers get from the book?

I hope people come away with a sense of wonder about this period of prehistory and the things that human beings have been able to do. I think that the Polynesian exploration and colonization of the Pacific was an amazing feat of imagination and endurance and creativity, and also possibly desperation—motives are hard to determine at this distance. There’s also one other thing, too, that really struck me as I worked my way methodically through the evidence: people have been so confident about certain ideas in certain periods of time, and you look back on those ideas and go, “Well, that was really wrong.” There is an interesting self-correction that takes place—people come along later and say, “You know, that’s just not quite right. Here’s another idea; maybe it’s better”—and I believe in that process. I’m an Enlightenment person. I do believe that the process of inquiry leads to greater understanding.