Caster Semenya, and fairness in sport (and life)

If we were to design athletic competition from scratch, how would we proceed? I think, given all the biases we’ve challenged or discarded since the first time athletic competition was tracked (sex, gender, race), we’d hope to find some way to match competitors in a way that created the spectacle required, and rewarded skill and effort, but did not rely on an arbitrary characteristic of humans to separate us into categories.