I believe Larry Nelson began sometime in his 20's!
True.
Larry Nelson began playing golf at age 21 upon his return from Army service in Vietnam. He broke 70 in his first year and won the PGA Championship twelve years later (and the U.S. Open two years after that).
I asked him in his prime if his goal was to become the game's greatest player.
"Well," he said with a little smile, "maybe the greatest player who ever started at 21."
I think that great golf becomes more difficult as you pick up the game in your 20s/30s/40s is that you're too intellectually involved and too physically strong to stay out of your own way. Little kids swing the way they do in large part because of a lack of strength, flexibility to burn, and they aren't trying to follow a multitude of swing thoughts. From what I've seen and read, adults who experience a lot of success quickly are almost all application, and very little theory. They spend more time making the ball do what they want it to do, and less time reading about it in magazines, etc. I've not only read about it, I've experienced it first hand.