Tooby and deVore argued that hominin evolution hinged on the exploitation of a unique 'cognitive niche'. We propose that a diversity of evidence indicates this was fundamentally a socio-cognitive niche. Analysis of hunter-gatherer ethnologies confirms unprecedented levels of egalitarian behaviour, cooperation and culture, in comparison to other primates and inferred ancestral stages. In conjunction with recent archaeological findings on the evolution of hunting, we use these data to reconstruct socio-cognitive changes in the course of hominin evolution, including joint planning and the impact of language. Precursors to these characteristics are inferred on the basis of recent observational and experimental studies of non-human primates' socio-cognitive abilities including cultural transmission, psychological attributions and understanding the requirements of cooperation. Presented by Andrew Whiten and David Erdal (Psychology, University of St. Andrews, UK). Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales; http://creativecommons.org/licenses/by-nc-sa/2.0/uk/