| Potentially edible!|
|—Hannibal Lecter, The Silence of the Lambs|
It may be done for many reasons, including extreme hunger and ritual, magical, or religious purposes.
The stereotype of human cannibalism is of fat (or lacerated), angry natives on a desert island boiling missionaries and other Western explorers in a large pot. Although culinary and ritual cannibalism is indisputable among the 15th century Mexica (Aztecs), controversy surrounds the historical descriptions of cannibalism in the South Pacific. Some scholars, like Gananth Obeyesekere, argue that the evidence for cannibalism in the South Pacific is poor and that the accounts of European explorers and missionaries may indicate nothing more than a form of "talking trash" or mutual misunderstanding in First Contact situations. There is "direct archaeological evidence for cannibalistic or para-cannibalistic practices in late prehistory on Easter Island, the Marquesas, New Zealand, Mangaia, and Fiji." In addition, one Fijian village did try to make amends for their ancestors allegedly eating Methodist missionary Thomas Baker. They gave back the "overcooked and slightly chewed shoe soles" to Baker's descendents.
There is growing evidence that the practice of cannibalism was common amongst Neanderthals, with speculation it may have contributed to their eventual decline. Hominins were not very filling compared to other foods that Neanderthals ate though. An adult male provides about 32,376 calories, which only provides enough food for a band of 25 adult Neanderthals for ⅓ of a day.
Early modern humans
The earliest known cannibalism among modern humans (Homo sapiens) occurred 14,700 BCE in a British cave, likely ritualistic cannibalism. "Human tooth marks consistent with chewing appear on human ribs and other lower-body bones from Gough’s Cave, as do stone-tool incisions."
In pre-modern medicine
Various parts of the human body have been used medicinally throughout the world, including in Egypt, Europe, Arabia (via the Persian Avicenna) and China. In traditional Chinese medicine, the parts of the body used were: hair, dandruff, ear wax, knee dirt, finger and toe nails, teeth, tartar, feces, meconium, urine and urinary components, gall (bile), gall stones, milk, blood, menstrual blood, semen, saliva, perspiration, tears, breath, bones, placenta, penis, and flesh in general.
Another case is of the Fore tribe, who suffered an epidemic of the kuru disease possibly due to it being passed on by ritual (mortuary) cannibalism. Members of the tribe do admit to eating human flesh, describing it as "sweet". In 2015, a protein variant was found among some members of the Fore tribe; the variant is believed to be an evolutionary adaptation that protects against kuru.
Custom of the sea
Cannibalism in extremis is an informal maritime law, known as one of the customs of the sea. Survivors of shipwrecks who have no other means of sustenance are allowed to eat the recently dead, or to even murder the morbidly ill. The survivors of the shipwrecked The Mignonette murdered and ate one of their own who was unconscious from hunger and seawater consumption. The survivors were convicted of murder in English court (1884 14 QBD 273 DC). They were sentenced to the death penalty but their sentences were later commuted to six months' imprisonment.
One can interpret the Christian practice of consuming communion wafers and blood-red wine as ritual symbolic cannibalism. The ceremony known today as the Eucharist was more than likely borrowed from Mithraic ritual practice. Part of the Mithraic communion liturgy included the words: "He who will not eat of my body and drink of my blood, so that he will be made one with me and I with him, the same shall not know salvation." Jesus reportedly says: "Most assuredly, I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in you. Whoever eats My flesh and drinks My blood has eternal life, and I will raise him up at the last day. For My flesh is food indeed, and My blood is drink indeed."  Indeed.
Most reasonable Catholic parishioners take this all as metaphorical; however, the Roman Catholic Church insists that the Host becomes the physical blood and body of Christ during transubstantiation—which can only mean that Communion, by the Church's own insistence, is actual cannibalism.
Do cannibals exist?
William Arens argued in The Man-Eating Myth (1979) that stories of cannibalism as custom or ritual in societies around the world could all be myths, essentially made up either by anthropologists or by natives telling credulous explorers, "the next tribe over eats human flesh!" He claimed that while people may have resorted to cannibalism in extreme situations, e.g. when starving to death, the evidence was not sufficient to prove that cannibalism has ever been practiced in stable societies with adequate food supplies. His argument was in large measure one for anthropologists to practice open-mindedness and skepticism, rather than a dogmatic conclusion that cannibals do not exist. Arens also suggested that social anthropologists as a profession needed exotic and gruesome stories such as this to justify their existence and keep themselves in work.
Arens was criticised by many of his peers, for using straw man arguments and adopting a "holier than thou" tone. P. G. Riviere called the book "dangerous" as promoting a myth and challenged Arens' attempts to dismiss accounts of cannibalism: e.g. Arens argued that the explorer Hans Staden who reported cannibalism among the Tupi people of South America would not have been able to understand the local language, but Riviere suggested Tupi was widely spoken throughout the region including by neighbouring peoples. In contrast Khaled Hasan praised the book for its analysis of colonialism and how rumors of cannibalism were used as part of a colonial project to justify stealing from and killing locals. It should probably be taken in that way, as the study of an idea and a call for skepticism, rather than as a conclusive dismissal of cannibalism.
Several horror films, such as The Texas Chain Saw Massacre (and its various declining in quality sequels and remakes) use cannibalism as a focal point. The Hannibal Lecter stories and films (Red Dragon, The Silence of the Lambs and Hannibal) has its namesake as a convicted murderer who ate his victims. The film Cannibal Holocaust had been accused of being a snuff film before it was conclusively shown to be fictional.
What is not cannibalism
It is easy to confuse a funerary practice such as ritual defleshing with cannibalism, since both involve butchering of the human body after death. However, ritual defleshing is not necessarily a prelude to cannibalism, and is a funerary custom practiced among many peoples worldwide, one noteworthy tradition of ritual defleshing is the Tibetan sky burial. Ritual defleshing has been practiced for many thousands of years by human societies, with the oldest known evidence of ritual defleshing going back to Neolithic Italy.
- Human growth hormone
- The Serpent and the Rainbow
- Fun:Soylent Green
- Fun:Tips for preparing and serving human babies
- Gananth Obeyesekere. 2005. Cannibal Talk: The Man-Eating Myth and Human Sacrifice in the South Seas. Berkeley: University of California Press.
- e.g., "dismembering, roasting, and non-funerary discard of skeletal remains"
- Introduction to Pacific Islands Archaeology by Patrick V. Kirch
- Fijians in cannibal curse ceremony
- BBC - Neanderthals were cannibals
- LiveScience — Neanderthal 'Family' Possibly Victim of Cannibal Attack
- Elizabeth Culotta 'Neanderthals Were Cannibals, Bones Show' in Human Nature, 1 October 1999, Volume 286, Number 5437, pp. 18 - 19
- Did Neandertals die off because of cannibalism and transmissible spongiform encephalopathies?
- Another problem with cannibalism: Humans actually aren’t very filling by Sarah Kaplan (April 6, 2017) The Washington Post.
- Ritual cannibalism occurred in England 14,700 years ago by Bruce Bower (April 24, 2015) Science News.
- Chinese Materia Medica: Animal Drugs by Bernard E. Read (1931). Peking Natural History Bulletin. Based upon the "Pen Ts'ao Kang Mu" [Bencao Gangmu] by Li Shih-Chen [Li Shizhen].
- Sydney Morning Herald — Cannibals may be feeding the lies
- Kuru: The Science and the Sorcery
- A protein variant can provide protection from deadly brain-wasting: Evolution found cure for prion disease spread by cannibalism by Tina Hesman Saey (1:34pm, June 11, 2015) Science News.
- A naturally occurring variant of the human prion protein completely prevents prion disease by Emmanuel A. Asante et al. Nature 522, 478–481 (25 June 2015) doi:10.1038/nature14510.
- Face-to-face with Abu Sakkar, Syria's 'heart-eating cannibal' by Paul Wood (5 July 2013) BBC
- See the Wikipedia article on R. v. Dudley and Stephens.
- See the Wikipedia article on Mithaism.
- Compare: Scotland, Nigel (2016). "A Meal of Ordinary Bread and Ordinary Wine". The New Passover: Rethinking the Lord's Supper for Today. Eugene, Oregon: Wipf and Stock Publishers. p. 48. ISBN 9781498218139. https://books.google.com/books?id=PzbkDAAAQBAJ. Retrieved 2019-01-23. "[...] as a number of scholars have pointed out, Mithraism, a religion of Persian origin, strongly influenced early eucharistic doctrine. Mithraism reached Rome by 67 BC and was fully embraced as an imperial cult in the first century. All creatures were supposed to be sprung from the bull that Mithras overcame and sacrificed before he ascended into heaven, where he guaranteed eternal life to all those who had been initiated as his followers. At the heart of its ritual was the sacred meal which had similarities to the Eucharist, including the use of bread and wine. The participants shared bread and wine and believed that as they did so they received the divine presence of Mithras."
- Mithraism - The sacred meal and the ascent to heaven
- John 6:51-55
- See the Wikipedia article on The Man-Eating Myth.
- "Reviewed Work: The Man-Eating Myth: Anthropology & Anthropophagy. by W. Arens", P. G. Riviere, Man, New Series, Vol. 15, No. 1 (Mar., 1980), pp. 203-205
- "Reviewed Work: The Man-Eating Myth: Anthropology and Anthropophagy by W. Arens", Khalid Hasan, Third World Quarterly, Vol. 2, No. 4 (Oct., 1980), pp. 812-814
- See the Wikipedia page on ritual defleshing for more information.
- "Stone Age Italians Defleshed Their Dead" from Science Magazine, published March 2015