BOSTON >> One is a neuroscientist-turned-sculptor, the other an activist and organizer. Taking different paths to the same goal, Bobbi Gibb and Kathrine Switzer outran Boston Marathon tradition and trampled the notion that women were too frail for a 26.2-mile race.

“When you’re trying to overcome a prejudice and do something you’re not allowed to do, how do you do it?” Gibb said this week as she prepared to serve as grand marshal for the 121st edition of the race, which Switzer will run again on the 50th anniversary of her landmark entry.

“I was hacking through the jungle. There was no path at all,” said Gibb, who actually hid in the bushes before becoming the first woman to run Boston, a year before Switzer strutted up to the starting line as the first official female entrant. “But I think we need all kinds of people. She’s an extrovert, I’m an introvert. Everybody has a gift to give.”

The Boston Marathon traces its origin to an ancient Greek battle and has a rich history of its own, filled with war heroes and Medford milkmen who persevered through oppressive heat, blinding rain and the occasional fox terrier that strayed onto the course.

But the story of the race’s distaff division didn’t begin until 1966, when it was still a fringe footrace of amateurs running only for an olive wreath and a bowl of beef stew.

Told she was too pretty for medical school — “the boys in the lab,” and all that — Gibb trained for the race in solitude while on a cross-country road trip in her Volkswagen Microbus , then persuaded her mother to drive her to the starting line by saying: “This is going to help set women free.” Jumping out of the forsythia bushes after the gun, she joined a field of 415 men and began what has only recently been recognized as the “unofficial era of women’s participation.”

A year later, Switzer told her coach at Syracuse, Arnie Briggs, about Gibb and said she also wanted to run Boston.

His response: “No dame ever ran no marathon.”

But Briggs struck a deal with her: If Switzer could complete the distance on a training run, he would bring her himself. They ran 26.2 miles together three weeks before the race, and Switzer suggested they go five more — just to be sure.

He passed out.

“And when he came to, he was so impressed,” she said. “He was like an evangelist and helped me sign up.”

The two pored through the race’s entry rules — Briggs insisted that Switzer, “a card-carrying member of the (Amateur Athletic Union),” could not be a bandit and would have to register — and found nothing about gender. Switzer, an aspiring journalist who thought her first name didn’t sound writerly enough, signed up using her first initial, K.

“I generally am pretty law-abiding. I don’t speed in my car,” Switzer said. “But am I bold? I’m also bold. And am I the type of person who asks for permission or begs for forgiveness? I ask for forgiveness.”

Although Gibb was also in the race for the second year in a row, it was Switzer in official Bib No. 261 that so offended race director Jock Semple that he ran after her, in his blazer and slacks, and tried to pull her off the course.

“We thought we were following the rules,” Switzer said. “And Jock thought we were trying to pull a fast one.”

Switzer’s boyfriend shouldered him out of the way, and Switzer ran on. (Semple, who died in 1988, maintained he was trying to protect his race from international rules that sanctioned only men’s marathons; by 1972, when women were first admitted to Boston, he and Switzer had become friends.)

Semple couldn’t knock Switzer off the course, but he did change her path: After the pictures of the scuffle were splashed across newspaper front pages , she found herself an unintended — but eager — spokeswomen for her gender.

“I wasn’t there to prove anything,” she said. “It wasn’t until Jock Semple attacked me did everything changed.”

Switzer went to work in PR and helped create the Avon International Running Circuit of 400 women’s races that showed the IOC there were enough women to fill out an Olympic field. When the women’s marathon was added to the Summer Games in 1984, the qualifiers at the U.S. Olympic trials were given trophies of a girl running.

It was sculpted by Gibb.

“Bobbi doesn’t like us to call her the hippie love child of the ’60s,” said 1968 Boston Marathon winner Amby Burfoot, noting that she was a serious student who switched from medicine to law after her path to med school was blocked. “But nevertheless, she’s a spirit child.

“And perhaps it’s an exaggeration to call Kathrine the corporate one, but there you are,” said Burfoot, whose book “First Ladies of Running” profiles some of the key women in the sport. “They just proved that they’re all unique and wonderful and there are different ways to get to the finish line.”

Gibb is working on a new sculpture — a life-sized bronze that she hopes will be the first of a woman along the Boston Marathon course. Switzer credits her for starting a movement, and Gibb acknowledges that it probably needed someone else to carry it forward.

“She (Gibb) said, ‘I’m not an activist or an organizer.’ Well, I am an activist and an organizer,” Switzer said. “It takes all kinds.”

Switzer went on to win the 1974 New York City Marathon and provide TV commentary in Boston for the last 37 years. In 2015, she created 261 Fearless, a nonprofit that uses running to empower women around the world; its logo is a rendering of her original bib, with one corner torn off from the struggle.

“What happened to me was a radicalizing experience. And it was one that made me bound and determined to change things for women,” she said. “Running had given me everything, and I wanted other women to feel that as well.

“Women who are empowered can change the whole society around them for the better,” Switzer said. “And running — I know it sounds crazy — but one foot in front of the other, it’s a transformational experience.”