Today, most people understand that animals can become extinct, whether as a consequence of a giant asteroid or because of our own pattern of habitat destruction, climate change and pollution that have endangered hundreds more. But just 200 years ago, the word "paleontology" hadn't been invented and Britain's Geology Society was just a few years old, its very existence a careful negotiation between science and religion, where some believed that Earth was formed on a specific date (Oct. 23, 4000 BC) and that it contained all of God's creatures, on whom He lavished loving and continual care.

Tracy Chevalier, author of "Girl With a Pearl Earring," immerses readers in that time in "Remarkable Creatures," a novel based on the lives of two English women who made significant contributions to paleontology in defiance of the restrictions of their era, gender and class. Their story takes place in the Regency Period made famous by Jane Austen, but though Austen's novels typically end with marriage, "Remarkable Creatures" subverts this familiar pattern by telling her story in the alternating voices of two women without "prospects."

Mary Anning is the working-class daughter of a Lyme Regis cabinetmaker, barely able to read or write and who sells "curies" (or fossils) to tourists to bring extra money to the family. Elizabeth Philpot is one of three middle-class unmarried sisters who are forced to move to the "remote, shabby watering hole on England's southwest coast" after the marriage of one sister and of their brother, the latter who made clear his intentions to sell the family property to buy another for himself and his new wife.

Unlike Austen's heroines, Elizabeth acknowledges that she will never have the "solid smugness" of married women but be relegated to the "formless and unpredictable" life of a spinster. Mary Anning senses her own differences too. It's not just that Mary's in a lower social class than the Philpots: Mary also survived a lightning strike as a toddler. The experience, she believes, "marks powerful moments of my life. . . . Sometimes I don't understand, but accept what the lightning tells me for the lightning is me." The aftereffect of her experience is that Mary is alert to fossils that wash up on shore or are buried in the cliffs of the Dorset coastline.

Fossil-hunting brings young Mary and 25-year-old Elizabeth together when the Philpot spinster seeks out Richard Anning to make a cabinet for her finds. Despite their differences, Elizabeth sees in Mary a kindred spirit who shares her passion for the fossils they both hunt. But while Elizabeth prefers spiral-shelled ammonites and fossilized fish, Mary hunts for the "verterberries" (vertebrae) of "monsters" that the children think are crocodiles.

As she matures, Mary becomes expert in having larger fossil specimens excavated and cleaning them, a process much like coaxing a sculpture from stone. When one of the "crocs" she and Joseph find proves to be more than 10 feet long and has strange paddles for forelimbs, the find (and those that follow) erases the debt left by Richard Anning at his death, helps her brother become apprenticed to an upholsterer and eventually draws the attention of geologists, including the renowned Georges Cuvier, who would later purchase her finds for his museum in Paris.

Despite her talent, Mary was outside the emerging scientific community -- and this made her ripe for what we'd call exploitation but which for the time was no more than the entitlement of upper-class men. Chevalier does an excellent job of showing both Elizabeth and Mary chafing under such strictures and how their work challenged the religious beliefs of the time.

Though some of the novel's more thoughtful passages involve those clashes, Chevalier is mindful that these were women operating in a world not far removed from Austen's, as Elizabeth acknowledges: "Life itself was far messier and didn't end so tidily with the heroine making the right match." Such messiness occurs when Mary gets stung by gossip after taking geologists out on a fossil hunt and falling for a collector above her class. Elizabeth experiences it when she recognizes that such visitors would never consider her, a spinster with little money, as marriageable despite her considerable knowledge.

Chevalier does an admirable job in juggling the social isolation and reprobation facing Mary and Elizabeth with their common passion for an emerging scientific field that had no room for women. Even though the period covered by "Remarkable Creatures" overlaps and goes beyond that of Austen (who, ironically, has some tangential business dealings with Mary's father on a visit to Lyme Regis), Chevalier bring to bear the harsher realities of life for 19th century women. This makes Mary's and Elizabeth's accomplishments as remarkable as the creatures they so relentlessly pursue.

Though it may be lacking the romantic frisson of an Austen novel, "Remarkable Creatures" is an engrossing, ultimately illuminating story of women finding fulfillment in shared passions and the bonds of friendship.

Woods is a frequent contributor to The Times