It is wellknown that many great mathematicians were prodigies.
Were there any great mathematicians who started off later in life?
It is wellknown that many great mathematicians were prodigies. Were there any great mathematicians who started off later in life? 

closed as no longer relevant by Felipe Voloch, Bill Johnson, Henry Cohn, Andy Putman, Mark Meckes Feb 3 '12 at 0:24This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center. If this question can be reworded to fit the rules in the help center, please edit the question. 


In the early 90's, I had a colleague who had been a professional tennis player before going back to a PhD thesis in mathematics. I'll hide his name since he is now in the middle of his career. 


Dennis Sullivan who won the 2010 Wolf Prize comments on this in his own words in the magazine published by the New York Academy of Sciences: http://www.nyas.org/Publications/Detail.aspx?cid=14047af09f26481c9b509434130c89db 


I don't know if Jean van Heijenoort counts as great, but his life story is amazing. 

