It's a pop-sci book, so it doesn't follow the "provide a footnote for each sentence" convention of academia, and often appeals to examples from popular culture. But the list of references does run 22 pages nevertheless.

For the content mentioned in this post, some cited papers were e.g. the one about people with serious but untreatable diseases not wanting to know about it as well as the author's own paper about the alliance hypothesis for human friendship.