Collective representations are the result of an immense cooperation, which stretches out not only into space but into time as well; to make them, a multitude of minds have associated, united and combined their ideas and sentiments: for them, long generations have accumulated their experience and their knowledge. A special intellectual activity is therefore concentrated in them, which is infinitely richer and complexer than that of the individual.

The languages and folkways of ancient peoples hold little relevance for us, except in one respect: the religions of the ancient world remain our religions. Though religions change, core features of the scriptures and rituals of the world's most popular religious traditions appear to have been conserved with remarkably high fidelity. We explain slow religious change from how religion facilitates cooperation at large social scales. At the end, we clarify how historians of religion, in collaboration with psychologists and computational biologists, might test and improve explanations such as ours.