Where a book like this can’t go is deep inside friendship: its particular intensity; its singular ease, but also its intricacy; the way it can wax and wane. The territory of novels and movies. But it will make you think about your own friendships, and perhaps it will cause you to worry, too, about those who seem (how?) to do without pals. I don’t believe that childless people like me are necessarily better at friendship: of my five closest female friends, two are mothers; my closest male friend is a father. But we all know couples who have sorely neglected their friendships, and we detect a certain sadness rising from them like toxic gas. Life is long. No one person can give you everything.
In normal times, “the endorphins triggered by the presence of friends tune the immune system and give us enhanced resistance to [...] bugs”, as Dunbar celebrates, but right now they might just give us Covid. Meanwhile, Zoom tends to force sociality into the straitjacket of the office-meeting form, representing another victory in the creeping corporatisation of personal life. “Eating and drinking with close friends needs to be done regularly,” Dunbar wisely reminds us, which will only sharpen the reader’s hunger for an eventual return to communal feasting. Perhaps we can even imagine a time when “eat out to help out” is no longer the name of a plague-spreading subsidy initiative but simply a slogan of good psychic health.