Had you asked two years ago I would have nominated the airplane, for it symbolizes the essence of invention by being composed of other inventions: the wheel, the bicycle, a glider, a prop, and a 12 horse power engine. The airplane is important because it diminishes our parochial view, it too changed the manner of warfare (Hey, nice bomber) and one can argue that it was an early form of the space shuttle. But if by important you mean sweeping, the utility of electricity is pivotal to so many things mundane and great, especially the broadcast of information, the A train, the monitors that tell me if my flight is delayed, this modern version of Gutenberg's press, and Les Paul's guitar. Thomas Edison received 389 patents for electric light and power, and Nikola Tesla patented his Apparatus for Transmitting Electrical Energy. Of course humans no more invented electricity than we invented flight, but utility is key. As I write I am preparing to go out for New Year's Eve, and packing a flashlight, just in case an old programming shut down code of 99 introduces us to the Y2K bug a year early. Should such a power failure occur then, the impact of electrical utility will be known.
wrote The Hominid Gang: Behind the Scenes in the Search for Human Origins