If you've taken part in a religious service, have you ever stopped to think about how it all came to be? How did people become believers? Where did the rituals come from? And what purpose does it all serve? This week, we bring you a July 2018 episode with social psychologist Azim Shariff. He argues that we should consider religion from a Darwinian perspective, as an innovation that helped human societies to thrive and flourish.