On Friday, January 2007 the world shrank into our palms as three revolutionary products — the iPod, a phone, and a breakthrough internet communicator — were unified to create the smartphones we know and love today. The first iPhone introduced in 2007 marked the fall of Qwerty keypad and stylus. (Large preview) iPhone was built to be comfortably used for one-handed operation, allowing for a smoother thumb movement across the screen.

https://www.smashingmagazine.com/2020/02/design-mobile-apps-one-hand-usage/