Evolution and context
The idea of human sacrifice has its roots in deep prehistory, in the evolution of human behaviour. From its historical occurrences it seems mostly associated with neolithic or nomadic cultures, on the emergent edge of civilization.
yam festival, early 19th century
Human sacrifice has been practiced on a number of different occasions and in many different cultures. The various rationales behind human sacrifice are the same that motivate religious sacrifice in general. Human sacrifice is intended to bring good fortune and to pacify the gods, for example in the context of the dedication of a completed building like a temple or bridge.
In ancient Japan, legends talk about hitobashira ("human pillar"), in which maidens were buried alive at the base or near some constructions to protect the buildings against disasters or enemy attacks, and almost identical myths appear in the Balkans (The Building of Skadar and Bridge of Arta).
For the re-consecration of the Great Pyramid of Tenochtitlan in 1487, the Aztecs reported that they killed about 80,400 prisoners over the course of four days. According to Ross Hassig, author of Aztec Warfare, "between 10,000 and 80,400 persons" were sacrificed in the ceremony.
Human sacrifice can also have the intention of winning the gods' favour in warfare. In Homeric legend, Iphigeneia was to be sacrificed by her father Agamemnon to appease Artemis so she would allow the Greeks to wage the Trojan War.
In some notions of an afterlife, the deceased will benefit from victims killed at his funeral. Mongols, Scythians, early Egyptians and various Mesoamerican chiefs could take most of their household, including servants and concubines, with them to the next world. This is sometimes called a "retainer sacrifice", as the leader's retainers would be sacrificed along with their master, so that they could continue to serve him in the afterlife.
Another purpose is divination from the body parts of the victim. According to Strabo, Celts stabbed a victim with a sword and divined the future from his death spasms.
Headhunting is the practice of taking the head of a killed adversary, for ceremonial or magical purposes, or for reasons of prestige. It was found in many pre-modern tribal societies.
Human sacrifice may be a ritual practiced in a stable society, and may even be conductive to enhance societal bonds (see: Sociology of religion), both by creating a bond unifying the sacrificing community, and in combining human sacrifice and capital punishment, by removing individuals that have a negative effect on societal stability (criminals, religious heretics, foreign slaves or prisoners of war). However, outside of civil religion, human sacrifice may also result in outbursts of "blood frenzy" and mass killings that destabilize society. The bursts of human sacrifice during European witch-hunts, or during the French Revolutionary Reign of Terror, show similar sociological patterns (see also Moral panic).
Many cultures show traces of prehistoric human sacrifice in their mythologies and religious texts, but ceased the practice before the onset of historical records. Some see the story of Abraham and Isaac (Genesis 22) as an example of an etiological myth explaining the abolition of human sacrifice. The Vedic Purushamedha (literally "human sacrifice") is already a purely symbolic act in its earliest attestation. According to Pliny the Elder, human sacrifice in Ancient Rome was abolished by a senatorial decree in 97 BCE, although by this time the practice had already become so rare that the decree was mostly a symbolic act. Human sacrifice once abolished is typically replaced by either animal sacrifice, or by the "mock-sacrifice" of effigies, such as the Argei in ancient Rome.