Cannibalism is common in the animal kingdom, but for humans it's the ultimate taboo
Vulnerable crow's feet tadpoles eat their smaller competitors to reach the eagle stage as quickly as possible. Gulls and pelicans are among the bird species that eat newborns for food or to prevent the spread of disease. In insect species such as praying mantis or Australian red-backed spider, males offer their bodies as final gifts to females after mating.
It's more common than we think in mammals too. Many rodent mothers can eat part of their young if they are sick, dead or too numerous to feed. Bears and lions kill and eat the offspring of adult females to make them more receptive to mating. Chimpanzees cannibalize unlucky rivals, usually infants, apparently for the simple opportunity of an additional protein.
For humans, however, cannibalism is the ultimate taboo. In fact, our aversion to cannibalism is so strong that consent and ethics are of little importance.
In one of our own experiences, participants were asked to consider the hypothetical case of a man who gave his friend permission to eat parts of him after his death from natural causes.
Participants read that this happened in a culture that allowed the act, that the purpose of the act was to honour the deceased and that the flesh was cooked so that there was no risk of disease. Despite this careful description, about half of the participants still insisted that the act was invariably wrong.
Even in the most difficult situations, the act of eating another human being's flesh remains almost elusive. Survivors of the famous 1972 Andean plane crash waited until they were almost starving to succumb to reason and eat those who had already died.
One survivor, Roberto Canessa, thought that by eating his fellow travellers, he would "steal their souls" and descend to "ultimate indignity" - even though he recalled that after the accident, like many others, he had said that he would be happy that his body would help the community survival mission.
Categorical disgust
The tragic anecdote above explains why humans are the exception to the rule of animal cannibalism. Our ability to represent the personalities of the living and the deceased is unparalleled. This deep connection between the person and the flesh can mean that, in some situations, cautious reasoning about the merits of cannibalism is overshadowed by our feelings of repulsion and disgust.
So why our disgust for human flesh but not for that of other animals? The philosopher William Irvine makes us imagine a ranch that raises fat babies for human consumption, just as we fatten and slaughter cattle for beef. Irvine suggests that the same arguments we use to justify slaughtering cows also apply to babies. For example, they would not protest, and they are not capable of rational thinking.
Although Irvine does not seriously advocate eating babies, the scenario is useful to shed light on our prejudices when considering the ethics of cannibalism. From an early age, we tend to consider categories, such as humans or cows, as having an underlying reality or "essence" that cannot be observed directly but that gives something its fundamental identity. For example, humans are intelligent and rational thinkers, we have personalities and a desire to live, and we form bonds with each other.
This psychological essentialism is a useful shortcut to guide our expectations and judgments about the members of the category, but it does not work very well when the typical qualities of this category do not apply, for example to death. That is why post-mortem consensual cannibalism is still the subject of such disgust. Even if we can resolve to consider it morally acceptable, we cannot silence our thoughts on the person from whom it comes.
The way we interact with animals shapes the way we classify them. Research shows that the more we think animals have human properties - that is, they are "like us" - the more likely we are to think they are disgusting to eat.
Adapting to the unknown
Although accusations of cannibalism have often been wrongly made to demonize groups, they are not absent from human history. The Fore people of Papua New Guinea reportedly participated in funeral cannibalism, believing that it was better for the body to be eaten by people who loved the deceased than by worms and maggots. In post-Renaissance Europe, parts of mummies were consumed for medicinal purposes.
We suspect that we could adapt to human flesh if necessary. Many people develop a disgust for all kinds of meat, while funeral directors and surgeons quickly adapt to the initially difficult experience of handling dead bodies. Our ongoing research with butchers in England suggests that they adapt easily to working with animal parts that the average consumer finds quite repugnant.
Fortunately for most of us, there is no need to overcome our repulsion in the foreseeable future. Some philosophers have argued that burying the dead could be a waste in the context of the fight against hunger in the world - but there are much more acceptable alternatives on the table than a bunch of humans. We can switch to eating more plants and less meat to conserve lost resources by feeding the plants directly to livestock. Insects can meet our protein needs, and there is the perspective of cultivated meat technology.
For the time being, we are as happy as you are to continue to accept the "wisdom of repugnance": human flesh, despite its biochemical similarities with that of other mammals, will remain firmly beyond limits.
