Physiology aside (there is more to athletics than just muscle mass, or body fat %), consider this point:

I concede that is theoretically possible, and it would be hard for me to disprove it, but it goes entirely against my intuition on this.

The issue is that the best female athletes are being annihilated by male athletes that aren't anywhere near the top of their game.

Whether you are using:

• Track & field (the top Olympic female 100m record of all time is the state-level high school-level male competition)
• Hockey (the US Women's National Hockey team - one of the top 2 in the world - trained against men's high school hockey teams)
• Soccer (the US Women's National Soccer Team, the top one this past year, was beaten by the Men's U19 team)
• Serena and Venus Williams, two of the top female tennis players ever, lost to a men's player ranked 203 at the time

Or any other sport, it is clear that there is a huge gap between the top players in the male sports and the top females in their sport.

At the professional level, letting men and women compete equally would all but annihilate women from playing.

Consider the fact that male athletes have historically peaked in performance in their age 27-30 years.

Now take for instance, soccer. Let's say we eliminate gender entirely and base it on ability. Would any women play in MLS? Possibly, but given that the best women's team lost to the men's U19 team, and that men do not peak athletically until they are 27, you're talking about very few women - if any - that would even make the finite number of spots in MLS, much less EPL.

And that's the issue - without said gender distinctions, you all but eliminate women's sports from being viable at the competitive levels. The NBA already has "minor leagues" like the D-League - all of which would annihilate any WNBA team. So let's say the WNBA league no longer has gender requirements - then the D-League or even sub-D-League level players would easily push out any women from playing at all.