[sykhic]

There’s a commonly held belief (myth?) that mathematics is a young person's pursuit in the sense of great discoveries. If you look at Erdös you see most of his great contributions occurring when he was younger and he was prolific throughout his life.

I think the downvotes come from your sentence about significant developments going under reported. I don’t think this happens at all. If someone discovers something great or profound in math no one cares about the age of the discoverer. Wiles was given a special prize because he was past the age of 40 when he proved Fermat's Last Theorem.

[sanxiyn]

Another example is Yitang Zhang and prime gap. He was over 50, so no Fields Medal, but he won many other prizes.

[Nokinside]

It's possible that things are changing over time.

When the mathematical knowledge increases, does the general character of the mathematical problems stay the same in the terms of required work and time? It's possible the problem set that young people can solve before they turn 40 will decrease after some time.