Our friends at Mental Floss offer a fairly comprehensive overview of cannibalism. Here’s an excerpt:
Exocannibalism is the consumption of the flesh of a person outside of one’s own social group, often as a way to intimidate an individual or group, steal another’s life force, or express domination of an enemy in warfare. Certain tribes in the Fiji islands maintained ritualized acts of cannibalistic “battle rage,” where captured enemy warriors were publicly tortured, killed, and consumed.
The accusation of exocannibalism may be even more damaging to enemies than eating them. When Christopher Columbus encountered the Carib Indians, he described them as “sub-human eaters of men,” labeling them inferior to Europeans and not much better than animals. They were seen as a dangerous “other,” and the murder of their people and theft of their land was easily justifiable because of that. The slur of cannibalism goes both ways, however. When the Spaniards arrived in Mesoamerica, and when explorer David Livingstone encountered certain African cultures, both the Aztecs and the African tribes assumed their white visitors were cannibals.