In 1922, Sybil Bauer, a student at Northwestern University, swam the 440-yard backstroke in just under 6 minutes and 25 seconds, beating the record held by a man and shattering notions of women’s athletic abilities.

The achievement inspired Ethelda Bleibtrey, another swimmer, to warn men that a challenge had been issued on “behalf of all womankind against the supremacy of man in the world of sports.”

“Eventually,” she wrote in a 1923 magazine article, “women will win as many of these prizes as men.”

Ms. Bauer, who was 19 when she smashed the record, set nearly two dozen swimming records and won the gold medal in the women’s backstroke at the 1924 Olympics, before dying of cancer at 23.

As for Ms. Bleibtrey’s prediction, it would take nearly five decades for many women to get the kinds of opportunities that men had to compete for championship laurels.

Before 1972, when Congress passed Title IX, forbidding sex-based discrimination in sports, about 30,000 women played college sports. About 294,000 girls were playing high school sports in 1971, compared with 3.7 million boys, according to the National Federal of State High School Associations.

A half-century later, the numbers are far closer. In 2019, 3.4 million girls participated in high school sports, compared to 4.5 million boys. In 2021, more than than 219,000 women participated in college sports, making up 44 percent of college athletes, according to the National Collegiate Athletic Association.

Title IX, which was extended to transgender athletes in 2021, turns 50 on June 23, an anniversary that has prompted historians and athletes to reflect on the long and continuing struggle for equality in women’s sports.

Who started women’s teams? Women.

In the late 19th century, female educators in American high schools and colleges began forming teams for girls and women to play sports like softball and basketball, said Susan K. Cahn, a historian at the University at Buffalo and the author of a book on gender and sexuality in women’s sports.

They sought a space for female athletes to flourish, and wanted to avoid the corruption they saw growing in men’s sports, where gambling was becoming prevalent, she said.

Rules were modified so that women would “adhere to stricter social norms,” said Chris Beneke, a professor of history at Bentley University.

For example, in basketball, women and girls for years could not steal the ball, were divided into three sections on the court and had to stay in assigned areas.

The point was “to make sure there wasn’t too much contact and too much exertion,” Professor Beneke said. “There was a real concern that they would hurt their organs.”

Specifically, he said, their reproductive organs.

In the early 1900s, men began coaching and developing women’s sports teams as the public grew more interested.

In turn, some news editorials began sounding alarm bells, Professor Cahn said.

Critics “raised the question whether a woman would become masculine,” she said. “Would women defeat men and the male sense of superiority?”

Last month, Sheree Bekker, who lectures on health and sports medicine at Bath University in England, made a provocative argument for why women’s sports teams were formed: to protect men.

“Women’s sport exists as a category because the dominance of men athletes was threatened by women competing,” she said in a widely shared Twitter thread.

Professor Bekker wrote the thread after Lia Thomas won the 500-yard freestyle at the N.C.A.A. women’s swimming championship in March, becoming the first transgender woman to win the competition and intensifying the debate about the inclusion of trans women in female sports.

Still, the idea that men carved out women's teams to avoid being humiliated is specious, Professor Beneke said.

“I don’t mean to diminish the role that bigotry played in restricting women’s athletic endeavors over the decades,” he said. “But male fears about being beaten by women has not been anything like the motivating factor that Professor Bekker suggests.”

Recovering stories of female dominance.

Professor Bekker said that she was trying to provide “another interpretation of why women’s sport exists as a category.”

Historically, the sports world has not responded favorably when women beat men, she said in an email.

In 1902, the figure skater Madge Syers became the first woman to compete at the World Figure Skating Championships, where she beat two men for the silver medal.

“She was the only one to skate the loop change loop without a mistake,” The Pittsburgh Press reported.

The following year, the International Skating Union barred women from the competition, concluding, in part, that a judge may not score fairly if he were romantically involved with a female athlete, and that it was generally “difficult to compare women with men.” In 1906, the first women’s competition was held.

In March 1931, Jackie Mitchell, a 17-year-old girl from Tennessee known for her curve ball, was signed to a one-year contract with the Chattanooga Lookouts, an all-male minor league baseball team.

The next month, when the team faced the New York Yankees, she struck out Babe Ruth and Lou Gehrig.

Rumors swirled that the strikeouts were staged. Soon after the game, Kenesaw Mountain Landis, the first baseball commissioner, voided her contract, some believe from embarrassment.

In 1992, the International Shooting Union had decided that year’s Olympics would be the last with women competing against men in shotgun skeet shooting. Then, Zhang Shang of China won the gold medal in that event, beating out the male competitors and raising hopes that the sport’s organizers would change their minds. But in 2000, when women were allowed in the Olympic event again, the competition was gender-segregated.

Many of these stories have been largely forgotten, suggesting there are more that haven’t been told, Professor Bekker said.

“These untold stories are illuminating,” she said. “I think these hidden stories, and what they might teach us, are worth speaking about.”

Is it time to mix it up more?

Since Title IX was passed, women have been competitive with men at the elite level in fields like rock climbing, surfing and endurance sports, like ultra running and biking.

Their achievements have led some to ask, Should we start integrating more professional sports?

Chad Carlson, an associate professor of kinesiology at Hope College, said administrators should at least consider the question where women appear to have equal if not greater advantages, like endurance sports, or those like fencing and shooting, where specific skills are emphasized over strength and speed.

“Why wouldn’t we?” he said. “If a greater opportunity to participate has led to greater performance, why won’t we allow females to participate with males to further explore the ceilings of performance?”

Professor Cahn said the question posed a conundrum for sports that emphasize speed and strength.

“If we had one professional basketball league it would probably just be very few women who could make those teams,” she said. “To create the most opportunities for women to play and excel, you’d still want to have separate competitions.”

Jessica Dolcimascolo, a senior at Colgate University who plays rugby, said allowing men and women to play together more could free female and transgender athletes from the kind of intrusive inspections they have undergone when their success has led to questions about their gender.

She said: “I would feel comfortable tackling some guy.”

Susan C. Beachy and Alain Delaquérière contributed research.