Women will be tall, like 6'5", with huge hips and big wombs, who naturally superovulate and produce small litters of offspring per pregnancy.
Men will be very small, like ~3'5", but completely proportional and really athletic, and super cute. Their bones will be denser than modern human bones and they will have really fast reaction speeds. In this way they will be vastly superior to modern males in combat and labor while costing far fewer resources. They will be, basically, supersoldier shotas.
All of them will be very intelligent.
Nations and societies that exaggerate and optimize sexual dimorphism and the two biological sexes in the way that I just described will out compete and dominate any society that goes in some other direction.
The giant women will be free to perform any jobs they want, helping to run and maintain society as Amazonian Queens as they birth huge amount of offspring very quickly, and the society will expand itself exponentially faster than any other combination of traits while maintaining superior military power. The small males will be heavily trained from a young age for military combat and specialized labor.
The fantasy of "The big strong male will beat up the little guy" isn't going to happen. He will be shot and ended very quickly. These elite small males will be cheaper to mass produce and superior in combat. In a one on one fight between the small guy with a gun versus some huge muscular guy with a gun the small one wins. He's smaller, more nimble and faster, is harder to hit as a target and will shoot and kill the other guy first the majority of the time. So the small males are both better individually, AND you can make more of them for the same amount of food and resources.
They will do all of it for a lower resource, food, and energy cost per equivalent population size. And they will have an exponentially greater rate of growth.
Any nation that doesn't do this will be rendered inferior and lose to societies that do.
