The drastic transformation of sports in recent decades, with women increasingly populating competitive arenas throughout the world, reached two significant milestones this week: Saudi Arabia agreed to send two women to compete at the London Olympics, meaning that for the first time all participating nations will have female athletes competing; and, also for the first time, the United States Olympic team will field more female athletes than male athletes.

The appearance of women from each of the 200-plus participating nations captures the sea change across the sports landscape. Until the 1984 Los Angeles Games, women were not even allowed to run a marathon. Less than 20 years ago, at the 1996 Atlanta Games, 26 countries did not send women.

“We need to celebrate and recognize” such advances, said Janice Forsyth, the director of the International Centre for Olympic Studies at the University of Western Ontario.

Saudi Arabia’s government and sports officials had faced mounting international pressure as the country continued a policy of allowing only men to participate in the Games. In March, the International Olympic Committee said it was confident that Saudi Arabia would send women to the London Games. But contradictory signals were sent by Saudi officials in the ensuing months. Meanwhile, two other Muslim countries — Qatar and Brunei — said they would send women to the Games for the first time.