Sylvester McCoy ( full name Percy James Patrick Kent-Smith) was born August 20, 1943 in Scotland.
Sylvester began show biz as a comedian and a stunt man in a travelling show called "The Ken Campbell Roadshow." He also did some one-man shows where he played Stan Laurel and Buster Keaton. You have to think that this kind of background carried over to Dr Who and maybe it's the reason he was selected as the seventh Doctor. Listening to BBC executives talk about about absolutely anything is pointless, but it may be that the reason they canned Colin Baker was that they thought he was too morose and sarcastic and they wanted the new Doctor to be the exact opposite.
McCoy played the Doctor through the "Survival" story in 1989 after which it was cancelled by the BBC for no coherent reason and believable reason that has ever been expressed.
Since Dr Who, Sylvester has had a full plate of various film and TV rolls. Some of the previous actors who have played the Doctors have been worried about typecasting, but that doesn't seem to have affected Sylvester.