We often think of the past as if it were another world — and in some ways, it is. The politics, religion and social customs of other eras can be vastly different from our own. But one thing historians and historical fiction writers alike often notice is the constancy of human emotion. The righteous anger of a customer complaining about a Mesopotamian copper merchant in 1750 B.C. feels familiar. Tributes to beloved household pets from ancient Romans and Egyptians make us smile. And we are captivated by stories of love, betrayal and sacrifice from Homer to Shakespeare and beyond.

In literature, letters, tablets and even on coins, we find overwhelming evidence that people in the past felt the same emotions we do. Love, hate, fear, grief, joy: These feelings were as much a part of their lives as they are of our own. And they resonate especially acutely in the bond between mother and child. Here are eight historical novels that explore the meaning of motherhood across the centuries.

Sometime in the 2000s, the producer Lindsay Doran asked her doctor for a book recommendation. “I’m reading that book everybody’s reading,” the doctor replied. “You know, the one about the shepherd who’s murdered and the sheep solve the crime.”

Doran had not heard of the book, “Three Bags Full,” a best-selling novel by a German graduate student (“No one’s reading it,” she recalls responding, inaccurately), but she was struck by what sounded like an irresistible elevator pitch. “Everything came together for me in that one sentence,” she said. “The fact that it was sheep rather than some other animal felt so resonant.”

Doran spent years trying to extricate the book from a complicated rights situation, and years more turning it into a movie. The result, opening Friday, is “The Sheep Detectives,” which features Nicholas Braun and Emma Thompson as humans, and Julia Louis-Dreyfus, Patrick Stewart and others giving voice to C.G.I. sheep stirred from their customary ruminations by the death of their shepherd, George (Hugh Jackman).

The film, rated PG, is an Agatha Christie-lite mystery with eccentric suspects, a comically bumbling cop (Braun) and a passel of ovine investigators. It’s also a coming-of-age story about growing up and losing your innocence that might have a “Bambi”-like resonance for children. The movie’s sheep have a way of erasing unpleasant things from their minds — they believe, for instance, that instead of dying, they just turn into clouds — but learn that death is an inextricable part of life.

“In some ways, the most important character is Mopple, the sheep played by Chris O’Dowd,” the screenwriter, Craig Mazin, said in a video interview. “He has a defect — he does not know how to forget — and he’s been carrying his memories all alone.”

“Three Bags Full” is an adult novel that includes grown-up themes like drugs and suicide. In adapting it for a younger audience, Mazin toned down its darker elements, changed its ending, and — for help in writing about death — consulted a book by Fred Rogers, TV’s Mister Rogers, about how to talk to children about difficult subjects.

The journey from book to film has been long and circuitous. “Three Bags Full” was written by Leonie Swann, then a 20-something German doctoral student studying English literature. Distracting herself from her unwritten dissertation, on the topic of “the animal point of view in fiction,” she began a short story “playing around with the idea of sheep detectives,” she said. “And I realized it was more like a novel, and it wasn’t the worst novel I’d ever seen.”

Why sheep? “I wasn’t someone who was thinking about sheep all the time,” Swann, who lives in the English countryside and has a dog named Ezra Hound, said in a video interview. Yet they have always hovered on the periphery of her life.

There was a friendly sheep that she used to see on her way to school. There was an irate ram that once chased her through the streets of a Bavarian village. And there were thousands and thousands of sheep in the fields of Ireland, where she lived for a time. “There were so many of them, and you could tell there was a lot of personality behind them,” she said.

A book in which sheep are stirred to action had to be a mystery, she said, to motivate the main characters. “In a lot of other stories, you would have trouble making a sheep realize there’s a story there,” she said. “They would just keep grazing. But murder is an existential problem that speaks to sheep as well as humans.”

Swann (the name is a pseudonym; she has never publicly disclosed her real name) found a literary agent, Astrid Poppenhusen, who brought her manuscript to market. Published in 2005, the book was translated into 30 languages and ended up spending three and a half years on German best-seller lists. (The German title is “Glennkill,” after the village in which it takes place.) Other novels followed, including a sheep-centric sequel, “Big Bad Wool,” but Swann never finished her dissertation.

Doran, the producer, read the book — now published in the United States by Soho Press, along with four other Swann novels — soon after hearing about it. She was determined to make it into a movie. Whenever she told anyone about the idea, she said, she had them at “sheep.”

The director, Kyle Balda (whose credits include “Minions”), was so excited when he first read the script, in 2022, that “I immediately drove out to a sheep farm” near his house in Oregon, he said in a video interview. “Very instantly I could see the behavior of the sheep, their different personalities. I learned very quickly that there are more varieties of sheep than dogs.”

How to make the sheep look realistic, and how to strike the proper balance between their inherent sheep-iness and their human-esque emotions were important questions the filmmakers grappled with.

It was essential that “the sheep in this world are sheep” rather than humans in sheep’s clothing, Balda said. “It’s not the kind of story where they are partnered with humans and talking to each other.”

That means that like real sheep, the movie sheep have short attention spans. They’re afraid to cross the road. “They don’t drive cars; they don’t wear pants; they’re not joke characters saying things like, ‘This grass would taste better with a little ranch dressing,’” Doran said.

And whenever they speak, their words register to humans as bleating, the way the adult speech in “Peanuts” cartoons sounds like trombone-y gibberish to Charlie Brown and his friends.

Lily, the leader of the flock, is played by Julia Louis-Dreyfus. It is not her first time voicing an animal in a movie: She has played, among other creatures, an ant in “A Bug’s Life” and a horse in “Animal Farm.” “When I read the script, I thought, ‘Wow, this is so weird,’” she said in a video interview. “It’s not derivative of anything else.”

Lily is unquestionably not a person; among other things, like a real sheep, she has a relatively immobile face set off by lively ears. “But her journey is a human journey where she realizes certain things about life she didn’t understand,” Louis-Dreyfus said. “There’s also the question of being a leader, and how to do that when you’re questioning your own point of view.”

Nicholas Braun took easily to the role of Officer Tim, the inept constable charged with solving the shepherd’s murder.

“The part was a little Greg-adjacent in the beginning, and I don’t really want to play too many Gregs,” Braun said via video, referring to Cousin Greg, his hapless punching bag of a character in the TV drama “Succession.”

“I’m post-Greg,” he said.

It takes Officer Tim some time to notice that the neighborhood sheep might be actively helping him tackle the case. But Braun said that unlike Greg, who is stuck in perpetual ineptitude, Tim gets to grow into a braver and more assertive person, a take-charge romantic hero — much the way the sheep are forced into action from their default position of “just forgetting about it and moving on and going back to eating grass,” he said.

Braun mused for a bit about other potential animal detectives — horses, say, or cows — but concluded that the sheep in the film were just right for the job. He predicted that the movie would change people’s perception of sheep, much the way “Toy Story” made them “look at their toys, or their kids’ toys, differently.”

“I don’t think people are going to be eating as much lamb after this,” he said.,

Siri Hustvedt was halfway through a new novel, about a writer tasked with completing his father’s unfinished manuscript, when her husband, the novelist Paul Auster, died from lung cancer.

Continuing that story in his absence felt impossible. They were together for 43 years, the length of her career. She’d never published a book without his reading a draft of it first.

Two weeks later, in the Brooklyn townhouse they shared, she sat down and wrote the first two sentences of a new book: “I am alive. My husband, Paul Auster, is dead.”

“It was the only thing I could write about,” she said.

She wrote about her feelings of dislocation: how she vividly smelled cigar smoke, even though Auster had quit smoking nine years before; how she woke up disoriented on his side of the bed and got into the bath with her socks still on; how she felt a kind of “cognitive splintering” that bordered on derangement. She had lost not only her husband, but also the person she had been with him. She felt faded and washed-out, like an overexposed photograph.

Those reflections grew into “Ghost Stories,” Hustvedt’s memoir about her life with and without Auster. Partly a book about grief and its psychological and physiological side effects, it’s also a revealing and intimate glimpse into a literary marriage — the buoyant moments of their early courtship, their deep involvement in each other’s work, their inside jokes (“I’ll have the lamb for two for one”).

She also writes publicly for the first time about the tragedies the family endured several years ago, when Auster’s son, Daniel, who struggled with addiction, took heroin while his infant daughter Ruby was in his care, and woke up to find she wasn’t breathing. He was later charged with criminally negligent homicide, after an examination found that her death was caused by acute intoxication from opioids. Soon after he was released on bail, Daniel, 44, died of a drug overdose.

A few months later, Auster started to come down with fevers, and doctors later discovered he had cancer. He reacted to the news as perhaps only a novelist would — lamenting that dying from cancer would be such an obvious, unsatisfying ending to a life marked by so much tragedy.

“He said so many times, it would make for a bad story,” Hustvedt said. “It was so predetermined, almost, and he hated predictable stories.”

Tall and lanky with short blond hair, Hustvedt, who is 71, met me on an April afternoon at the elegant, art and book-filled townhouse in Park Slope where the couple lived for 30 years. She took me to the sunlit second floor library, where Auster spent his final days, surrounded by his family and books. “He loved this room,” Hustvedt said.

“I’ll show you his now quiet typewriter,” she said, leading me down to Auster’s office on the ground floor, which felt as tranquil and carefully preserved as a shrine. A desk held a small travel typewriter, an Olivetti, and next to it, his larger Olympia. “Click clack, it really made noise,” Hustvedt said.

Auster rose to fame in the 1980s thanks to postmodern novels like “City of Glass” and “Moon Palace,” which explore the mysteries and unreliability of memory and perception. Hustvedt gained renown for heady and cerebral literary novels that include “The Blazing World,” “What I Loved” and “The Summer Without Men.”

They were each other’s first readers, sharpest editors and biggest fans. They even shared characters — Auster borrowed Iris Vegan, the heroine of Hustvedt’s 1992 novel “The Blindfold,” and extended her story in his novel “Leviathan,” published the same year. (Critics and readers assumed she had used his character, not the other way around.)

“We were very different writers and always were, and that was part of the pleasure in the other’s work,” Hustvedt said.

Friends of the couple who have read “Ghost Stories” said they were moved by Hustvedt’s loving but not hagiographic portrait of her husband.

Salman Rushdie, who visited Auster just a few days before he died, said Hustvedt’s vivid portrayal of Auster — who was witty, warm and expansive, always ready with a joke — captured a side of him that was rarely reflected in his public image as a celebrated literary figure.

“He’s very present on the page,” Rushdie said. “They were so tightly knit, and Paul was Siri’s greatest champion. They were deeply engaged in each other’s work.”

Hustvedt was 26, a budding writer who had just published a poem in the Paris Review, when she met Auster, 34, after a reading at the 92nd Street Y. He was wearing a black leather jacket, smoking, and she was instantly smitten.

They went downtown to a party, then to a bar in Tribeca, and talked all night. He was married to the writer Lydia Davis, but they had separated. He showed her a photo of his and Davis’s 3-year-old son, Daniel. They kissed as she was about to get into a taxi, and he went home with her to her apartment on 109th Street.

Shortly after they began seeing each other, Auster broke it off and told her that he had to return to his wife and son. She won him back with ardent, unabashed love letters that she quotes in “Ghost Stories”: “I love you. I’m not leaving yet, not until I am banished.”

In 1982, a few days after Auster’s divorce, they got married. They were so broke that guests had to pay for their own dinners.

Their writing careers evolved in parallel, but Auster’s fame eclipsed Hustvedt’s. She often found herself belittled by interviewers who asked her what it was like to be married to a literary genius, and whether her husband wrote her books.

“People used to ask me what my favorite book of Paul’s was; no one would ever ask him that,” Hustvedt recalled.

When Hustvedt complained about the disparity, Auster joked that the next time a journalist asked what it was like to be married to him, she should brag about his skills as a lover.

The slights persisted even after Hustvedt had established herself as a formidable literary talent. “One imagines that will go away, but it didn’t,” she said. She’s sometimes felt reduced to “Paul Auster’s wife” even after his death: At a recent reading, a fan of his work asked if she took comfort in reading his books in his absence, as if the real loss was the death of the literary eminence, not the man she loved.

She felt the weight of his reputation acutely when Auster died, and news of his death spread online just moments after he stopped breathing, before the family had time to tell people close to him.

The shadow Auster’s fame cast over the family became especially pronounced when scandal and tragedy struck.

In “Ghost Stories,” Hustvedt details a side of Auster’s personal life that he closely guarded: his relationship with Daniel, whose drug use and shiftiness was a constant source of worry. As a teenager, he stole more than $13,000 from her bank account, her German royalties. In 2000, Auster and Hustvedt learned that Daniel had forged his transcripts from SUNY Purchase after he had promised to re-enroll; he hadn’t, and kept the tuition money.

After each breach of trust, she and Auster forgave him.

“I have to leave the door open, just a crack,” Paul said about Daniel, Hustvedt recalls in “Ghost Stories.”

She writes about rushing to the hospital in Park Slope, where Daniel’s daughter was pronounced dead: “It’s the image of her small, perfect dead body in the hospital on Nov. 1, 2021, that forces itself on me.”

The shock of Ruby’s death, followed by Daniel’s arrest and overdose, was made even more unbearable by the media frenzy. Auster and Hustvedt were hounded by reporters, and made no comment.

“We were not in a position to speak about it when it happened, it was all so shocking and overwhelming and trying to deal with your feelings was more than enough,” Hustvedt told me.

But she felt she had to write about Daniel and Ruby in “Ghost Stories” because their lives and deaths were a crucial part of the family’s story, yet had been reduced to lurid tabloid fodder, she said.

“It would not have been possible to write this book and pretend that these horrible things didn’t happen,” she said. “I also didn’t want the horrible things to overwhelm the book, and that’s a tricky thing, because it’s so horrible, you feel it has to be there, but it isn’t the whole story.”

Before he died, Auster told Hustvedt he wanted that story to be told.

“I didn’t feel that I was betraying him,” she said.

Auster and Hustvedt’s daughter, Sophie Auster, a musician who lives in Brooklyn, said reading her mother’s memoir was painful, but she also felt her father’s voice and presence in its pages.

“Opening the book was extremely difficult for me, but you just sink in,” she said. “She doesn’t let you sit in the sorrow for too long. There’s a lot of life and a lot of joy.”

Hustvedt found it strange to write “Ghost Stories” without sharing drafts with Auster, her habit throughout her career. But often, his voice popped into her head.

“I kind of heard him in my ear, saying things like, ‘That’s a wavy sentence, straighten that thing out,’” she said.

After finishing the memoir, Hustvedt went back to the novel she’d been working on when Auster died. She realized she had to rewrite the first half entirely.