Even online, the neocortex is the limit That Facebook, Twitter and other online social networks will increase the size of human social groups is an obvious hypothesis, given that they reduce a lot of the friction and cost involved in keeping in touch with other people. Once you join and gather your “friends” online, you can share in their lives as recorded by photographs, “status updates” and other titbits, and, with your permission, they can share in yours. Additional friends are free, so why not say the more the merrier?

In the wild, grooming is time-consuming and here computerisation certainly helps. But keeping track of who to groom—and why—demands quite a bit of mental computation.