There's a "skills gap" present in Math aptitude tests that appears in countries where the status of women is worse
This may be partially explained by the mistreatment. However, there is a giant elephant in the room of "sex equality": sports. The all-female teams are invariably weaker, than the all-male ones — and compete separately. Co-ed teams are required to have a certain number of women (2 players for a 6-member volleyball team, for example). Soccer World Cup just ended — did you see a single female player there? Are you going to attribute it entirely to sexism?
It is not all about muscles either — women aren't any better at chess, than they are at at swimming or running. It is so bad, the international chess body(ies) had to create a separate title: Chess Woman Grandmaster (CWG) — because so few of them could become actual, non-gendered, Chess Grandmasters (CG). Indeed, only one percent of CGs are female.
Sure, there are individual women, who are stronger and smarter than an average male. But the strongest man is stronger, and the smartest — smarter, than the strongest and smartest woman, respectively. We just don't look or smell as good. And we can't give birth...
Sure, there are arguments politely trying to explain away this disparity. But they fail.