I had an idea of a concept a while ago.
If a planet that for some reason or another had only one giant continent like Pangea, but bigger, for more distinct habitats and giant lakes assuring isolation between living organisms.
If humanoid and sapient species starts to develop like our ancestors and us, the pressure for natural selection would be far higher than it was with us, because they still can meet guaranteeing plenty of conflicts to happen, like Neanderthals and our species.
After a whole lot of time, don't know how much, nature greets us with a humanoid species that when push comes to shove can always reproduce if there is too little of one sex or another some of them starts to express the right genes changing to suit the right need.
Of course, in my opinion, this species eradicates the others and because they can always reproduce their genetic diversity and number of adaptations to specific habitats is on a whole other level.
My question is if there is proof of concept to my logic
My mistake, sorry.
PS - The individuals of my species have both internal sexual organs but only in a crisis does their genitalia changes somehow. They don't have sexual dimorphism as we do, height, total mass, muscle mass, fat percentage, etc. Are more related to habitat adaptation then sex.