[joe_the_user]

Hmm,

Andrew Wile began work on proving Fermat's theorem in 1986 at 33. He finished first presented the proof in 1993 at age 40. He was not eligable for a Fields Medal, which I personally think is a travesty (An award reserved for the class of people considered most fit in the field? What's the justification there ). http://en.wikipedia.org/wiki/Andrew_Wiles

Raymund Smullyan received his PhD at forty and has made significant contributions to logic. http://en.wikipedia.org/wiki/Raymond_Smullyan

It has been hypothesized that mathematics has grown so large that mathematicians are now more likely to make contributions because of the amount of material which it is necessary to learn.