One can imagine a kind of hormonal arms race or genetic arms race, whether it's to do with height or IQ, conceivably, in the future. So it's limitless, and that's another of the features that sets it apart from medical intervention.
In the eighty or ninety years I have given to this subject, trying to trace out the meanderings of their twisty little minds, the only thing that I have learned for certain about women is that when a gal is gonna, she's gonna. All a man can do is cooperate with the inevitable.