Two faces that appeared on my Instagram feed in recent months gave me pause. One belonged to John Travolta at Cannes. The other to Carla Bruni on a date night with her husband, former French President Nicolas Sarkozy. Both looked recognisably themselves, yet, they both also looked oddly unfamiliar. Their looks have provoked speculation about cosmetic enhancement, though never acknowledged by them. Bruni has previously denied having had work done.In any case the feeling lasted only a second: a flicker of unease, as though I were looking at people who had become approximations of themselves.There is a name for that sensation. In a 1970 article, the Japanese robotics professor Masahiro Mori described what he called the “uncanny valley”. He found that robots that were designed to look as human as possible often provoked discomfort in people. That was a surprise, since the benefit of humanoid robots was supposed to be that we humans would trust them more.What scares us about a robot that almost passes as human? One explanation may be that we sense danger when encountering something we cannot categorise easily as either human or not. Another is that the features that seem “off”, such as glossy skin or frozen expressions, resemble signs of disease or death.Carla Bruni at the Cannes film festival in May. Photograph: Olivier Chassignole/AFP/Getty ImagesFor a humanoid robot, triggering the uncanny valley sensation means failure. But what does it signify when a human provokes it? In 1956, the German-Austrian philosopher Günther Anders published a collection of essays entitled The Obsolescence of the Human. Anders, Hannah Arendt’s first husband, argued that technological progress would push humans to develop a novel form of self-contempt. Faced with the perfection of mass-produced goods, humans would come to regret their “bodily clumsiness” and “corporeal imprecision”. They would grow ashamed of being merely the result of the “blind and uncalculated, highly archaic process of procreation” rather than of careful design.Anders wrote:Each day out of machines arise