In reality, the choice of what sex a child will have when they are born are currently up to the genes that get activated when the egg and the sperm exchange DNA. Unless there is human interference, it's all up to luck - which sperm gets to the egg first, what genes it is carrying are active, how all that interacts with the genes in the egg - hundreds of variables. No wonder there can be mix ups where a boy feels like a girl or a girl feels like a boy.
Seems like every new generation of humans wants to change the world. Sometimes for the good, sometimes for the bad, and sometimes you can't tell until after the event in question goes into effect. Each new generation affects the outlook on life and expectations for the now, and the older generation in general feels their world is falling apart around them. Therefore is strife born and old evils pop up again, as those who don't like the changes fight to keep them at bay.
Mankind is making many changes to our mother, the Earth in it's mad rush to dominate the planet. The Earth fights back in the only way open to it - eruptions, mega-storms, tsunamis, etc. Still mankind's dominance of the world continues as we learn how to alleviate the damage the Earth can cause to us. We use up more and more of the limited resources on this planet - converting the natural to manmade wants - damning other species to extinction and destroying the land on which we live.
We will be the cause of our own destruction or will the universe respond by striking us down? Seems for all the knowledge available to us of the world, the natural processes that we need to survive, the diversity we should be embracing (human and other life forms) some of mankind takes to the dark path and tries to destroy it all. Greed, desire for power, dominance - all lead to war and atrocities. The seeds of mankind's destruction. Zombies anyone?
After the dark, comes the light of day. Perhaps one of our generations will be able to evolve past the point of destruction and evil that has plagued humans for all our past historical generations. Maybe sometime in the future, if we survive ourselves and the chaotic universe, a generation will come that will lead mankind past the destructive forces that still hold sway in our societies. One can only hope.