My 7 year old ds didn't talk until he was well over 3. I read several books on speech delay and Autism. Yes, he had many symptoms of autism. Except that he enjoyed interacting with people but just wouldn't speak. He communicated his desires and emotions through facial expressions, laughing and gestures. Then one day he started talking in complete sentences and asking ton's of questions. He has always been his own person even as a baby, we ended up figuring it was a quirk of his personality.

He is extremely observant and figures things out very quickly.
He taught himself how to read and picks up basic math skills with little of no repetition.