In a Darwinian world, providing honest information to competitors is, at face value, a losing strategy. If information is valuable, no one should give it for free, and if it has no value, no one should pay attention to it. This Darwinian principle is the main reason why most animal species don’t communicate usefully about their environment. There are exceptions, such as bees or ants, but these animals, unlike us, communicate with kin exclusively. To explain how human communication came to emerge in a Darwinian world, one must see it as an instance of social signalling. People choose their friends according to their ability to be interesting or relevant in conversation. In this chapter, social signalling using language is shown to be an evolutionary consequence of another unique feature of homo sapiens.