Communication for collaborative computation: two major transitions in human evolution.

This paper presents and defends the following theoretical arguments: (1) The uniqueness of the human condition lies in the fact that only humans engage in , where different individuals work together on shared computational challenges. Collaborative computation is the foundation of our cumulative cultures. (2) Collaborative computation requires individuals to engage in , where senders do not just send messages to receivers-but also send them instructions that the receivers are obliged to follow in the course of computing the messages. (3) The process of human evolution was driven throughout by the invention and development of tools of instructive communication. (4) In this process, two separate major transitions should be identified. The first was made possible by the toolkit of representational gestures (pointing, eye contact, manual demonstration, pantomime and more) that Merlin Donald called the toolkit of . Mimesis allows for collaborative computation as long as the information requiring computation is available for direct experiencing by the participants. The second was made possible by , the tool that allowed its users, for the first time, to engage in collaborative computations of information they did not experience together-through the systematic instruction of the mental computations of imagination. This article is part of the theme issue 'Human socio-cultural evolution in light of evolutionary transitions'.