You could be a sacrificial victim for the benefit, for the cohesion of the group. But any gene that would allow you to be exploited by the group would be selected out because genes are selected much more quickly than groups. Also, I think it's too easy to use our own intuition that we like to bond over music, over religion and so on, but that is itself a part of our psychology that needs an explanation. Why would beliefs in invisible entities make a group coherent more? You can't take that for granted. That's as much of a puzzle to a psychologist as…