As Hafner and Lyon note in Where Wizards Stay Up Late, ARPANET e-mail was immediately popular—the network’s first “killer app.” “It just happened,” wrote Henderson and Myer, “and its early history has seemed more like the discovery of a natural phenomenon that [sic] the deliberate development of new technology.”

While the ARPANET was still used for transacting “serious” scientific business, its users eventually realized that these incidental communications were a serious business, too. As Ian R. Hardy notes in “The Evolution of ARPANET email”:

Electronic mail over the ARPANET quickly became an integral component in institutional communications patterns. Primarily for this reason the ARPA community began to view the ARPANET as an essential utility on a par with the telephone system, electricity, or jet transportation. “People began to depend upon it,” Frank Heart recounts. “Especially as electronic mail became an important component of the use of the system, people began to assume it was going to exist.” This general assumption demonstrates a profound reliance on email within the ARPA community. The ARPANET came to be viewed as an indispensable resource precisely because it carried network mail.

The world does not operate under monastic rule, with its inhabitants locked in their cells, reading and learning only for purposes of quiet contemplation. When most people learn or read something interesting, they want to take that material and pass it along.

Usenet was, in its way, just as important as e-mail in the role it played in the development of the Net. Dubbed “the poor man’s ARPANET” by early users, Usenet consisted of a collection of discussion groups devoted to single topics—the programming language Unix, to start, but later involving a cornucopia of topics ranging from koala bears to the Chicago Cubs. Before Usenet, online communications had been primarily restricted to scholars, students, and scientists with access to ARPANET terminals—a fairly limited group. But Usenet was open to anyone with a Unix machine. In “The Social Forces behind the Development of Usenet,” Michael Hauben observed that Usenet became popular among “people who didn’t have access to the ARPANET [but] were hungry for similar opportunities to communicate.”

The appeal—one that will seem familiar to modern Internet users—was in chatting with people who shared your intense interest in certain topics, and participating in distinct communicative groups. “The ideas that exist on Usenet come from the mass of people who participate in it. In this way, Usenet is an uncensored forum for debate—where many sides of an issue come into view,” writes Hauben. More so than e-mail and listservs, then, Usenet used the Internet as a medium for unexpected yet engaging communications—an important step in the development of any human communications system.

In his ICCC ’72 paper “Three Characterizations of Communications Revolutions,” Bell-Northern researcher Gordon Thompson noted Jane Jacobs’s characterization of the city sidewalk as a communications medium: an environment that “permits interesting and unexpected messages to be exchanged at a low level of commitment.” Usenet was, initially, the sidewalk of the Internet.

Although Usenet still exists, it has largely been made obsolete by the World Wide Web, which is what most people now mean when they discuss the Internet. (“Internet” is simply a term for the infrastructure through which network data are transferred—Web sites, e-mails, instant messages, file transfers, and so on. “World Wide Web” specifically refers to the hyperlinked pages generally accessed by a browsing utility like Firefox or Internet Explorer.)

When the World Wide Web debuted in 1991, it seemed that we were finally at the point of a true procognitive system, where people would be edified and improved by virtue of the information with which they were now able to freely interact. (In his book Weaving the Web, Web inventor Tim Berners-Lee echoed J.C.R. Licklider when he wrote that “the Web will be a place where the whim of a human being and the reasoning of a computer coexist in an ideal, powerful mixture.”) But the information itself wasn’t the point.

Justin Peters is editor-at-large of the Columbia Journalism Review.