I don't mean to discount the Fields specifically here, but most of the Fields stuff is pretty much couched in the sphere of pure maths. How are Fano varieties used to improve our lives? Why is Mordell/Fatling's Theorem important? In what ways are we using the Burnside problem today? I will also point out that most of the Fields medal recipients come from Europe or Japan, both of which have had declining birth rates for some time.

Understand that I work in the realms of scientific research. Do we have some super smart people on our team? Yes. Our team also consists of about 40 people working on our specific set of problems. None of us is going to win a Nobel prize. But I think that we have contributed significantly to our field.

I will leave the fuller discussions of the Industrial Revolution and the Renaissance to another time perhaps, but those were times of great scientific and artistic productivity, yet they followed eras of decreased birth rates.