When you set up World Generation, the "Traditional Sports Team Genders" explains that you can either uncheck the traditional sports team genders box to give, say, the football team a more inclusive amount of genders, or that you could max/reduce the sliders and the game would populate the missing traditional genders with other genders.
I dunno I tried latter by highly populating the world seed with females and reducing males, and it seems the football team is all male. Probably would have been better off just unchecking traditional sports team genders, but as described the latter option might not (always?) work.