Bonobo cannibalism

Ewen Callaway in New Scientist:

More individuals got a taste of the infant than is typical when the apes share meat. They also spent 7 hours eating the body longer than they take over a similar-sized monkey. Some even played with it. "If they just think of it as another piece of meat, why do they behave differently with it?" he asks.

Of course you’ll see a lot of rare things when you spend enough time watching. If the average individual can go through her entire life without eating the flesh of a conspecific, it’s not probably very important. But seeing it rarely puts it in the range of behavior – common enough in evolutionary timescales for either natural or cultural selection to pick it up if it were useful.