Humans are strikingly different from our close relatives, the great apes, in mind, behavior and life history. We propose that the evolution of these derived features
was a consequence of the adoption of cooperative breeding by early Homo. Among the species that adopted it, cooperative breeding generally produces changes in psychology toward greater prosociality and greater cognitive abilities. We propose that in our ancestors,
the major energetic inputs to breeding females due to cooperative breeding explain the derived features of human life history and lifted energetic constraints on brain enlargement. Moreover, in combination with great-ape level cognitive abilities, the cooperative-breeding psychology led to the evolution of many of the unusual socio-cognitive traits that we now celebrate as uniquely human: pedagogy, extensive cumulative culture and cultural norms; intensive
and nearly indiscriminate within-group cooperation and morality; a cooperative declarative communication system known as language; and full-blowntheory of mind.