Cliff-edged fitness functions

Writing a commentary on a 2004 BBS article by Jonathan Burns  about why genes that cause schizophrenia persist inspired a month of thinking about what kind of explanation could possibly work. Finally, I recognized that traits with an asymmetric fitness function 

The commentary has generated a lot of follow up. 

And I featured the idea in Chapter 14 of my book on evolutionary psychiatry: Nesse, R. M. (2019). Minds unbalanced on fitness cliffs. In Good Reasons for Bad Feelings: Insights from the Frontier of Evolutionary Psychiatry (pp. 245–261). Dutton.