Learned cannibalism -- also known as customary cannibalism -- is a category of anthropophagy quite different from survival cannibalism. Survival cannibalism is a form of cannibalism practiced when people feel they must eat the flesh of members of their own species in order to stay alive. Survival cannibalism has occurred throughout human history -- often after shipwrecks or in wilderness situations -- basically, whenever people have become desperate and hungry enough.

Learned cannibalism, however, is not a last resort; people who practice this form of anthropophagy are not driven by necessity. At the same time, this term does not refer to anomalous cases, such as singularly deranged, Hannibal Lecter-style cannibals. Learned cannibalism is passed down from one generation to the next and is typically part of some sort of socially sanctioned or ritualized behavior. Anthropologists subdivide learned cannibalism into endocannibalism and exocannibalism.

Endocannibalism takes place when the flesh of a member of a kinship group is consumed by someone else in that group. Many cultures perform religious rituals in which members of a family or group will consume the flesh of a dead relative or ally. For example, in the past, the Fore peoples of Papua New Guinea would prepare ritually specified parts of a dead person's corpse and feed them to the relatives of the deceased. After a man passed away, the ritual dictated that his sister should eat his brain. Other members of the family received other parts. Years of this practice are believed to have subjected these tribes to outbreaks of Kuru, a deadly viral infection that produces neurological symptoms similar to Creutzfeldt-Jakob disease.

While endocannibalism may seem repugnant to people who are unfamiliar with the practice, it is typically meant as a respectful gesture. Ritual exocannibalism -- meaning the consumption of the flesh of an out-group person -- is most often a practice used to intimidate an unfriendly group or to steal someone's power or energy. For example, there is some indication that different cultures in history, including some past groups of the Iroquois and Fiji peoples, practiced cannibalism in the context of war. These warriors would capture foreign enemies, they would torture and maim their captives in a public setting, and then they would finish the ritual with the consumption of the captives' flesh. Such practices have continued, most often in wartime, all over the world: Even in 2003, the United Nations investigated charges that Congolese rebels had been using cannibalistic practices as part of their war effort.