Michael Balter writes in Science about a meeting called "Culture Evolves": "Probing Culture's Secrets, From Capuchins to Children."
There appears to have been a deliberate ambiguity in the conference title -- is it the evolution of culture, or the evolution of the cognitive abilities underlying culture? Apparently both. Ignoring the distinction usually leads to confusion. Culture does not evolve in the same way as genes do.
In one group of capuchins, the team's long-term observations have allowed them to witness a rare event: the emergence of a new tradition. In what Perry calls a "bizarre" and "high-risk" ritual, the monkeys poke each other's eyeballs. One monkey will insert his or her long, sharp, dirty fingernail deep into the eye socket of another animal, between the eyelid and the eyeball, up to the first knuckle. In videos Perry played for the meeting, the monkeys on the receiving end of the fingernail, typically social allies, could be seen to grimace and bat their eyelids furiously (as did many members of the audience) but did not attempt to remove the finger or otherwise object to the treatment. Indeed, during these eye-poking sessions, which last up to an hour, monkeys insisted on the finger being reinserted if it popped out of the eye socket.
Why would the monkeys do something potentially dangerous? Perry suggests that capuchins, which, like humans, are highly cooperative and live in large groups, use this apparently pain-inflicting behavior to test the strength of their social bonds.
If this were happening in a zoo, wouldn't we call it a behavioral pathology?
Of course, if it were happening in a fraternity...oh well, never mind.
A new tradition that appears within one group does not need an adaptive explanation.