Okay, yes. Yes, if smart people have fewer children because they have better access to contraception, and nobody is, like, doing anything about that, that could be a problem, yes. This is frankly something Keltham has never even imagined as a catastrophic failure mode of a civilization, but that could have been, over past generations, a very large cumulative problem, yes. How good that anyone on Golarion has finally potentially noticed this is an issue. The good contraceptive technology that dath ilan uses is unfortunately not trivial on the tech ladder, but Keltham can explain how to research things ever and they can hopefully find some better makeshifts than whatever people are doing now.
That interbreeding stuff is fascinating, from a seeking-hidden-order perspective, but Keltham will explain why in more length later.
Does Cheliax have any kind of thinking that's about, like... why are there equal numbers of men and women, at least among humans? Assuming there are. If there aren't, Keltham is going to have to check a few things and then potentially back out a number of his assumptions.