An unsentimental and slightly creepy theory if you like that kind of thing is that both humor and aesthetic sensibilities evolved as a group defense against psy

An unsentimental and slightly creepy theory if you like that kind of thing is that both humor and aesthetic sensibilities evolved as a group defense against psychopathy. Some species including ours gain an advantage among competing species through co-operation among themselves. A species using this strategy is vulnerable to freeloaders within its ranks who optimize their own survival at the expense of the group. The theory goes that an empathy deficit in individuals correlates with other deficits (e.g., in a sense of humor) that might be harder for the individual to hide and therefore easier for the group to detect. By ostracizing the psychopath on that basis, the group increases its overall fitness.