Why the objections to McIlroy or Johnson on the women’s tour? For the same reason golf courses provide separate tees for women, the same reason the WNBA uses a smaller basketball than their male counterparts, the same reason there are thriving women’s leagues in tennis, soccer, bowling, and dozens more. It is not about the social construction of gender; it is about biological differences that bear directly on performance.

Biological males and females differ systematically in size, strength, speed, height, lung capacity, and agility. Acknowledging those differences is separate from respecting how any individual self-identifies. Given our widely shared opposition to discrimination, those physical differences are the only reason to permit separate events. If gender differences don’t matter for a particular sport, then the rationale for separate events is weaker than our liberal ideal of non-discrimination.

We would never permit, much less require, this kind of gender separation in chess tournaments. It would violate our basic norms demanding equal treatment unless there are very powerful reasons to treat people differently. Those reasons and their persuasiveness will differ from sport to sport. They hardly matter for equine events like show jumping and dressage. They probably don’t matter for target shooting. But they do matter for archery. Top male athletes pull their bows with higher “draw weights” than do top females, so they can shoot arrows with flatter trajectories, less affected by crosswinds. The differences matter in golf, too. On the men’s professional tour, the average drive is 295.5 yards. On the women’s tour, even the longest hitter doesn’t drive the ball that far.