It may not quite qualify as a Silicon Valley parable, but it does not fall too far short. It is impossible, now, to imagine the social media platform X — the thing that we all still think of, reflexively, as Twitter — without that distinctive, pointed ouroboros nestled at the foot of each post, the one that serves as a gauge, a currency and a vector of virality.

The retweet — the capacity to share, quickly and easily, a contribution that you enjoy or endorse or otherwise wish to bring to the attention of others — was the innovation that made Twitter work. It gave a niche idea its purpose, turning a curious app into a transformative social, cultural and political force and, eventually, a billionaire’s plaything.

It was not, though, deliberate. Retweeting was not designed by the cadre of developers who founded Twitter. It did not exist in the early versions of the app. There was, in its first iterations, no way of amplifying the best (or, later, worst) content that emerged from the doomscroll. The app’s founders had not, it seems likely, considered what their invention would be for.

Instead, the retweet was the brainchild of the platform’s early adopters, “bootstrapping a tool for spreading news and popular posts,” as the journalist Taylor Lorenz writes in Extremely Online, her history of social media and the rise of influencer culture. “Twitter did not integrate retweeting into its product until late 2009,” almost three years after its launch, she notes.

Lorenz’s book is full of stories like this. YouTube was initially designed to be a dating site. Instagram’s founders were intensely wary of advertising and product promotion, fearing that the venal impulses of capitalism might interfere with their app’s aesthetics. LinkedIn was not built for finance bros to brag about “the grind.”