The act or practice of eating members of the same species, e.g. humans eating humans, or dogs eating dogs. This has been practiced by various tribal groups in the past in the Amazon basin, Africa, Fiji, and New Guinea, usually in rituals connected to tribal warfare. The Chaco Canyon ruins of the Anasazi culture have been interpreted by some archaeologists as containing evidence of ritual cannibalism. Individual cases in other countries have been seen with mentally unstable persons, criminals, and, in unconfirmed rumors, by religious zealots.
It is worth noting that early reports of human cannibalism are somewhat suspect. During the years of British colonial expansion slavery was actually considered to be illegal, unless the people involved were so depraved that their conditions as slaves would be better than as free men. Demonstration of cannibalistic tendencies were considered evidence for this, and hence reports of cannibalism became widespread. Other more contemporary reports have also been called into question. The well known case of mortuary cannabilism of the Fore tribe in New Guinea which resulted in the spread of the disease Kuru has also been questioned by those claiming that although post-mortem dismemberment was the practice during funeral rites, cannabilism was not. This case, however, is well documented and not seriously questioned by modern anthropologists. Fijian cannibalism is also generally accepted as historically factual.
For some species, cannibalism under certain well-defined circumstances, such as the female black widow spider eating the male after mating, is believed to be a common, if not invariable, part of the life cycle. In vertebrates (except for many fish), cannibalism is not generaly observed to be uniformly routine or widespread for any given species, but may develop in extremis such as captivity, or a desperate food shortage. For instance, a domestic sow may eat her newborn young, though this behavior has not been observed in the wild. It is also known that mice and rats will eat their young if their nest is repeatedly threatened by predators. In some species adults are known to destroy and sometimes eat young of their species to whom they are not closely related--famously, the chimpanzees observed by Dr. Jane Goodall. Some of these observations have been questioned (for example by Stephen J. Gould) as possible products of sloppy research. For example, while there are many observations of female praying mantises eating their mates after copulation, there are no known observations of this occurring in the wild; it has only been observed in captivity.