How many turns did you win? My criteria for science also includes turns played, science wins are very doable with less than 800 science, and waiting to get over 3000 science would have added dozens or more extra turns to the game.
I think it was just after turn 1000 on marathon. I wasn't exactly rushing for a science victory, but I still won while most of the AI were in Atomic era. It was only on Emperor, though.