A fascinating AskMetaFilter thread set off by the question “Why didn’t I say anything until I was three?” It’s full of interesting anecdotes and references to studies, and one commenter quotes this great Einstein story:
Otto Neugebauer told the writer the following legend about Einstein. It seems that when Einstein was a young boy he was a lake talker and naturally his parents were worried. Finally, one dat at supper, he broke into speech with the words “Die Suppe ist zu heiss.” (The soup is too hot.) His parents were greatly relieved, but asked him why he hadn’t spoken up to that time. The answer came back: “Bisher war Alles in Ordnung.” (Until now everything was in order.)
I think I once knew how old I was when I started talking, but I’ve forgotten. Anyway, late talking doesn’t seem to be a cause for concern.