Archaeologists have found that in prehistoric times, when humans had only the most rudimentary technologies available to them -- e.g. clothing, fire, stone tools -- many separate prehistoric human tribes had invented the (entirely frivolous) flute; Steven Johnson's invention discussion considers why this is the case.
In Johnson's summation, necessity isn't the only mother of invention. He posits that humans are just as driven by a desire for play, and these playful inventions have led to some of the great innovations in the world.
For example, Johnson delves into computers in his invention discussion. Though the standard line is that computers were invented for military purposes, Johnson traces the germ for the idea of computers back to ancient Islamic scholarship. Inventors in Baghdad over 1,000 years ago created the first programmable music box, which initiated the conception of software versus hardware. Yet, despite the fact that this led to the massively practical invention of computers, the initial machine was purely for something frivolous: music.
So, as Johnson puts it, "You'll find the future wherever people are having the most fun."