This is also true for women - in my life many of my friends who are over 40 are getting their PhDs and doing incredible research. Also see composers and painters: so much of our great works in history are done by older people. Perhaps because I studied classics, I always assumed that I would only start doing my 'real' work after the age of 40 and I'm personally really enjoying building my career with the next 30-40 years in mind.