The first line of her first novel came to Jacqueline Kelly as she was suffering through a particularly oppressive summer in her century-old farm house, 40 miles south of Austin, Tex.: “By 1899, we had learned to tame the darkness but not the Texas heat.”

“It’s a huge house, built for an enormous family, but it is falling down and the air-conditioning is entirely inadequate,” says Kelly of the home she shares with her husband, Robert, two dogs and three cats. “I was lying there in the middle of the day wondering, How did people stand it a hundred years ago? and, immediately, a whole family sprang to life. They basically dictated the first page to me and I wrote it down.”

The result--nearly a decade later--is The Evolution of Calpurnia Tate (Holt), a coming-of-the-modern-age tale starring “practically-12-year-old” Calpurnia Virginia Tate (called Callie Vee), an only daughter sandwiched between six brothers. Callie’s spirited recollection of seeking emancipation from the corseted strictures of her day through scientific inquiry has earned Kelly four starred reviews, a feat that most surprised the author, who didn’t know she was writing a novel, or that it was a work for children, when that first sweaty inspiration struck. Callie’s original incarnation came in a short story, which Kelly shared with her critique group. “They said, 'We think this is a novel,’ ” she recalls. “I was appalled by the idea. I’d never written a novel before.”

She came around, submitting the first chapter of Callie’s story to the Texas Writers’ League’s annual Manuscript Contest in 2002. Serendipity intervened: the judge was Marcy Posner of Sterling Lord Literistic, who awarded her first prize and asked to see the entire novel. “Then I had to write the thing,” Kelly says.

Though Calpurnia Tate is Kelly’s first book, “author” is her third profession. Born in New Zealand and raised in British Columbia, Canada, she practiced law (“12 very stressful years as a litigator”) before returning to medical school. Dr. Kelly still sees patients twice a week at a clinic in Austin. “My heart is really in writing, but I don’t see myself giving up my medical practice. I’ve been at this clinic for 27 years,” she says.

Her scientific knowledge certainly helped in crafting Callie Vee, whose choice of reading material is Darwin’s On the Origin of Species and whose preferred activity is collecting botanical specimens. Laura Godwin, Henry Holt’s publisher and Kelly’s editor, had recently acquired Deborah Heiligman’s Charles and Emma, about the nexus of science and Christianity inside the Darwins’ loving and supportive marriage. Kelly’s manuscript was the middle-grade fictional yin to Heiligman’s YA nonfiction yang.

“When we got the manuscript, it was love at first sight, but we weren’t the only clever ones--there was competition,” says Godwin. “So I asked to speak to the author, and we learned we had much background in common. We both grew up in Canada, and my father was a botanist. It was one of those wonderful moments where you find out you not only love the writing but there’s this nice connection, too.”

Godwin gave Kelly a two-book contract, but she isn’t sure what she’ll write next. She’s working on something inspired by Kenneth Grahame’s The Wind in the Willows, a book she loves, and is thinking about a sequel that follows Calpurnia into the 20th century. Godwin professes no worries that her author will find another field to conquer. “It’s quite astonishing, but she says those other two careers were practice careers. What she really wants to do is write,” Godwin says. “And I’m all for that.”

From the editor, Laura Godwin: "My first thought upon reading this manuscript was, Who wouldn't love this book? A novel that begins on a sweltering summer's day in 1899 that is described so vividly we can feel the Texas heat. Add to that an effervescent protagonist who is tenacious, un-self-conscious and a girl who likes science. The fact that she is surrounded by six brothers and wonderful grownups who actually act like real grownups do only makes the story all the more irresistible. The manuscript was so obviously fun, thoughtful and beautifully written that deciding to publish it was easy."