Animals communicate by exchanging signals that contain information. The type and amount of information contained in a signal is restricted and shaped by long lasting evolutionary processes. In the course of human evolution, the emergence of a special set of cognitive abilities and social motivations changed the way in which information is transmitted by a given signal. First, the interpretation of a signal depends on whether it is used with the intention to provide information. Second, humans expect signals to be cooperatively intended and therefore expect them to provide relevant and useful information. Finally, the signal is interpreted in the light of the facts and beliefs that are shared between the interlocutors. In this chapter I will argue that these changes enabled humans to flexibly create and understand signals in unprecedented ways. This in turn changed the way that information was transmitted across individuals and generations.