Papyrus rolls and Twitter have much in common: They were their generation's signature means of "instant" communication. Indeed, as Tom Standage reveals in his scintillating new book, social media is anything but a new phenomenon.

From the papyrus letters that Cicero and other Roman statesmen used to exchange news across the Empire to the rise of hand-printed tracts of the Reformation to the pamphlets that spread propaganda during the American and French revolutions, Standage chronicles the increasingly sophisticated ways people shared information with each other, spontaneously and organically, down the centuries. With the rise of newspapers in the nineteenth century, the nature of communication changed; increasingly, especially as radio and television, the "mass media," came to dominate in the twentieth century, information was centrally controlled. However, with the advent of the Internet, the story has come full circle, and the spreading of information along social...