In addition to the other comments about pre-iPhone/Android smartphones, another part of the story are the devices that preceded even those, the personal digital assistant (PDA). There's the well known PalmPilot and various Windows CE PDAs like the Compaq iPaq and Dell Axim and even earlier, now largely forgotten devices like the HP 95LX and 100LX, a DOS based palmtop PDA that was really quite capable for 1991, and probably a few even earlier than that. So the evolutionary path to the modern smartphone probably stretches to 30+ years.