The cover of Tracy Chevalier's 'Remarkable Creatures' is seen in this undated handout photo. REUTERS/Penguin USA/Handout

Philadelphia ? A woman picking at bones in the dirt … sexy stuff for a book?

Could be … if that woman helped midwife an entire new understanding of the history of life.

That’s the warm heart of Tracy Chevalier’s new book, “Remarkable Creatures.”

In what is often called an era of great nonfiction, Chevalier renders true stories into truer-than-fact fiction. Her 1999 novel “Girl With a Pearl Earring” has had successful lives as book, play and film. Although often classed glibly as “historical novels” or “nonfiction novels,” her books really explore the human underpinnings of history.

She says that as she writes, “I am trying to get smart on the facts — but even more, to get smart about the emotional truths behind the facts.”

By phone from her home in London (American-born, Chevalier has lived in England since 1984), she says, “Once I know I’m going to write on a particular subject, it is, of course, important to get smart about it, read all I can, do my homework. But that’s the same as for any novelist. When Jonathan Franzen was writing ‘The Corrections,’ for example, he probably had to do a lot of research about Lithuania.”

But there’s a point, she says, when the writer steps past the facts.

“Remarkable Creatures” comprises three interlocking dramas. The first is the remarkable story of Mary Anning, a poor Englishwoman who discovered, in 1811, the first complete fossil skeleton of an ancient aquatic beast we now call ichthyosaur. Mary’s is the ultimate “citizen scientist” story, in which an ordinary person makes a historic scientific breakthrough.

The second drama is that of a friendship, between Anning and Elizabeth Philpot, an older woman from London. Elizabeth meets Mary when the former moves to the seaside town of Lyme Regis, where Mary lives. As Mary shares her discoveries, Elizabeth supports and encourages her new friend.

“As I wrote the book,” Chevalier says, “Elizabeth became just as important a figure to me as Mary had. As a character, Elizabeth was a real gift: She gives us a perspective from which to see Mary. I read about their friendship and found it odd. Elizabeth was 20 years older, much better off than Mary, yet they were friends, across class and age lines. I wanted to explore that friendship. We know less about her than about Mary, but it’s clear she was more experienced, more educated. She says and thinks things, questions beliefs more than Mary would.”

Elizabeth hunts for fossils with Mary and fights to promote her discoveries in the male-dominated world of science. Chevalier says: “It becomes a book about women’s roles in society and about the nature of friendship.”

The book’s third drama, just as breathtaking, relates to the first. We watch as the minds of the times resist, recalibrate, renegotiate with the new reality announced in Mary’s discovery. It’s one of the most dramatic of all human dramas: the human mind changing. Such was the central intellectual drama of the 19th century, as advances in geology, paleontology — and, of course, biology, in the mountainous figure of Charles Darwin — changed age-old assumptions about what we are and where we came from.

Facts and fiction

Between the pleasure of story and the instruction of facts, a novelist like Chevalier negotiates a narrow strait: “My books, I hope very much, are not merely entertainment — although I do want readers to turn the pages and be entertained. But I also want them to discover things about the world.” Such discovery, she says, is not textbook learning, but a wider sort, “to feel a greater sense of connection with the world.”

Although she had to master much geology and science while working up the book, she says, “Science is not really my topic. I have kept that sense of discovery more than the specific facts.” She took one other thing from the writing of “Remarkable Creatures”: a new hobby, fossil collecting. “I hadn’t been keen on it before,” she says, “but now I go out so much that my son is a little bored with it now.”

Her new book appears during Darwin’s bicentenary. Coincidence, Chevalier says: “I wasn’t aware of it until I was partway through the research!” She knows that a book on this topic may bring special attention now, in the midst of Darwiniana and the “God Wars.”

“A lot of people accept evolutionary theory without knowing what came before,” Chevalier says. “If you ever want to know how creationists think, you can meet people who lived their whole lives, as people had for centuries, in a creationist universe. And my book isn’t by any means anti-creationist — it’s about how the sands began to shift.”

So many true stories — how does Chevalier choose which ones to make into books?

The process, she says, is far from obvious. “If I actually try to sit down and figure out what’s next, it doesn’t work.”

Beguiling subjects

Mary came upon her when Chevalier and son Jakob visited a dinosaur museum in Dorsetshire. “There was a little display there about Mary Anning,” Chevalier says. “I was immediately attracted to her. She was one of these eccentrics England does so well: independent, never married, uneducated, yet she discovered quite amazing fossil specimens that shook the foundations of what people believed about the world. And she was struck by lightning as a baby! ‘Wow,’ I said. ‘It doesn’t get any better than that.’ “

From that moment on, Chevalier had a sudden need to write about Mary — much as when in 1997 she looked at a beguiling face in a Vermeer painting and felt moved to tell the story behind the painting. So was born Griet, the girl of “Girl With a Pearl Earring,” and the world Chevalier invented around her.

Similarly, a Cees Nooteboom article about the six medieval “Lady and the Unicorn” tapestries stirred Chevalier to explore the story behind their mysterious creation. That became her 2003 novel “The Lady and the Unicorn.”

As for what’s next, Chevalier’s blog gives a hint: “I don’t want to say much about my next book as it’s still in its infancy. All I’ll tell you is that it’s about a Quaker family working on the Underground Railroad in 19th-century Ohio.”