The rope around her ankles is in case Megan Callahan-Beckel gets trapped in the wolf den.

"I just click my heels like Dorothy and they pull me out," she says with a grin.

At 21, Callahan-Beckel is a veteran of puppy pulls, also known as den dives. She'll wriggle into the den where a mother wolf has given birth, a passage as deep as 35 feet and often barely wide enough to squeeze through. Sometimes, the tunnel collapses on her and the Dorothy act becomes more urgent.

On this sunny day in May, she's escorted by a dozen staff members and volunteers from the Wildlife Science Center in northern Anoka County, carrying padded poles to fend off Chief, the alpha male who's the father of this litter. One staffer carries a paintball gun, the last resort if Chief gets too aggressive.

In the end, the task is easy. Chief watches warily but keeps his distance. And Iris, the 11-year-old mother, has already moved the newborns from her underground den into a wooden shelter, about the size of a piano crate, that's been provided for her. Callahan-Beckel lifts the lid and climbs in.

Oohs and aahs and delighted chuckles burble from the crowd as, one by one, she hands out three Rocky Mountain wolf pups, 12 days old, with fuzzy, gray-brown pelts and their barely opened eyes squinting against the sun. Callahan-Beckel cradles the last pup against her neck and makes soft whining sounds, mimicking an adult wolf.

The little 2-pound furballs will eventually grow to be adults weighing anywhere from 90 to 120 pounds. But before they reach adulthood, they've got a task to perform.

They're going to help scientists figure out how wolves became dogs.

Deep in the past, sometime between 15,000 and 40,000 years ago, one of man's most feared predators became his new best friend.

Through generations of evolution, wolves transformed into dogs. The common wisdom has been that humans gradually domesticated the wild animals. But now, some scientists believe that's not how things played out.

Video (02:02) The Wildlife Science Center in Stacy is helping scientists gain insight into how the great wolf-to-dog transformation happened.

Survival of the friendliest

"One of the main ideas for how dogs happened is, humans fell in love with wolf puppies and decided to raise them. That's sort of the old folk story," said Brian Hare, a professor of evolutionary anthropology at Duke University and director of the Duke Canine Cognition Center in Durham, N.C.

"My team thinks there's a different hypothesis: It wasn't that humans chose wolves, it's that wolves chose humans."

As humans began to live in larger communities, their garbage provided a reliable source of food. And wolves noticed. As Hare explains it, some wolves figured out that they could make a good living, food-wise, by cozying up to the humans.

In other words, the friendliest wolves could leave scavenging behind and dine at the never-ending buffet.

The evolutionary result?

"By selecting for friendliness and attraction to humans, you get a lot of the traits that are selected for dog domestication," Hare said. "The idea is that the wolf pup was selected to be nonaggressive and tolerant of humans."

But testing that hypothesis requires a steady supply of wolf pups. That's where the Wildlife Science Center, founded in 1990 by Peggy Callahan and her husband, Mark Beckel, comes in.

For several years now, Hare has been working with the center, home to more than 100 wolves — as well as assorted black bears, mountain lions, bobcats and foxes. (By comparison, an estimated 2,300 to 2,600 wolves are living in the wild in Minnesota.)

Most of the center's wolves were born here, although it does sometimes take in adults from the wild. Chief, the pups' father, came from the wild in British Columbia.

The captive wolves will produce perhaps two to three litters each year, with three to six pups per litter. By studying the early development of those pups and comparing it with the early development of dogs, researchers hope to gain insight into how the great wolf-to-dog transformation happened.

"The resources and the expertise of Peggy and her team are absolutely vital if we want to answer that question," Hare said. "There isn't another place I know in the world where first-generation wild wolves move into captivity as newborn puppies.

"If we really want to know where dogs come from, Peggy and the Wildlife Science Center are where it's at."

bove, Peggy Callahan, Wildlife Science Center founder and executive director, lifts a 12-day old wolf pup from its den to hand to another staff member. Below, workers check the den while adult wolves look on.A change of perspective

Callahan, 58, found her life's work as a second-grader in Rochester when she read a book by wolf biologist Dave Mech. She wrote him a letter, and he replied. Years later, after she graduated from Carleton College, Mech helped her get a job at what was then a federally run wildlife refuge at the Carlos Avery State Wildlife Management Area in Forest Lake.

When the feds decided to close the place down in 1990, Callahan and Beckel, a veterinary surgeon, took it over. They moved the nonprofit to its current location in 2017.

In normal times, thousands of schoolchildren visit the wildlife center each year, and it also hosts college classes. Although the COVID-19 pandemic has put an end to those activities for now, life at the center goes on with a handful of key staff and interns tending to the animals. Callahan misses the wonder she sees among the young visitors, many of whom have never seen a wolf — or any wild animal, for that matter.

"When people see a living wolf, it changes their perspective," she said. "To see the light in people's eyes that I feel, it translates into an understanding of protecting what's out there."

Her daughter has seen it, too.

"Kids will come in saying they hate science, and then leave thinking it's the coolest thing," Megan Callahan-Beckel said.

he designated licker

"That was smooth as silk," Callahan-Beckel says as the crowd gathers around the three pups. (They left two others with the mother to be raised by her.)

A gate opens and in dashes Poppy, a 5-year-old German shepherd and designated licker. Newborn wolf pups don't know how to excrete their body wastes. Normally, the mother licks the puppies' genitals to stimulate excretion. But for the pups that are removed from their mother, Poppy handles the job with enthusiasm.

The pups will sleep with Callahan-Beckel and be bottle-fed for a week or two; then they'll start getting some meat introduced to their diet. As adults, they'll live on roadkill, lab animals, trapping carcasses and other animals donated to the center.

"We haven't bought any food in years," Callahan says with a laugh.

Soon, researchers will begin working with the human-raised pups: observing, playing games, charting their reactions. It's all part of a scientific effort to shed light on how humans and animals formed a lasting bond. And Hare thinks he's closing in on the answer.

"Based on the data we now have, the [answer] is pretty clear," he said. "Because they wanted to have access to the human food supply, they remade themselves to be more attractive to humans."

And based on the fuzzy evidence in Callahan-Beckel's arms, it's hard to argue.