As the guys at Autour D'un Cafe pointed out, the Playstation controller has de-evolved over the years. There was a lot of inbreeding at first, but that changed after a night of heavy drinking.
As the story goes, the DualShock got it on with a '60s era Baterang and the Gaming Gods retaliated—smiting their unholy spawn. This event cleared the slate, so to speak, and the evolutionary process started all over again. [Autour D'un Cafe via Geekologie]