[quote=Etcetera]
They have a huge country, correct? We have evidence that it was once lush, full of trees and plains. Perhaps female engineering managed to restore it to that state,and create an enormous empire through that.
[/quote]

But then so would every other arid country. Remember, even the best kept secrets never last. The atomic bomb was kept away from the rest of the world for only a few years before the schematics were stolen by Russians and distributed worldwide. 

I suggest, in order to keep the plot a little more simple, the y chromosome breaks down within the span of 2-4 years, dropping the male to female birth ratio to 1:10 so we only have to rewrite 20 or so years of human history rather than 40.