The social origins of consciousness.

We present the social origins of consciousness hypothesis, according to which the ability to coordinate with group members was the original adaptive function of consciousness. We offer three arguments. The phylogenetic argument presumes that consciousness is widespread among existing animals, and that widespread capacities are probably evolutionarily old. Early animals relied on consciousness to solve a problem that arose during the Cambrian, when animals first became behaviourally flexible-how to predict others' behaviour and stay together as a group. The argument from neuroscience points to evidence that even very simple brains have the capacities for social rewards and pains, and that modern brains retain close connections between the substrates for social cognition and affect. The deep adaptive alignment between social pain and harm to animals develops an argument originally proposed by William James (1890). We provide evidence that in preference tests, bodily pain is preferred to social pain in a wide range of species. We offer two approaches to testing the hypothesis-the salience of social stimuli test and the overattribution of agency test. Working under the social origins of consciousness hypothesis could lead to significant breakthroughs in research, especially by focusing on simpler systems than are currently studied.This article is part of the theme issue 'Evolutionary functions of consciousness'.