Researchers believe human sacrifice (remains in Papua New Guinea shown) played a role in building stable communities with social hierarchies

Human sacrifice may seem brutal and bloody by modern social standards, but it was a common in ancient societies.

Now, researchers believe the ritualised killing of individuals to placate a god played a role in building and sustaining stable communities with social hierarchies.

In particular, a study of 93 cultures across Asia, Oceana and Africa, has found the practices helped establish authority and set up class-based systems.

Human sacrifice was once widespread throughout these Austronesian cultures, which used it as the ultimate punishment, for funerals and to consecrate new boats.

Sacrificial victims were typically of low social status, such as slaves, while instigators were of high social status, such as priests and chiefs, installing a sense of fear in the lower classes.

Since the European colonisation of Central America 500 years ago - when Conquistadors were horrified by the Aztecs' sacrificial practices - experts have claimed ritualised killings were a form of social catharsis.

They described them as a justification for political conflicts and even a source of protein when combined with cannibalism.

Researchers from the universities of Wellington and Auckland, the Max Plank Institute for the Science of Human History in Germany, the Australian National University and the Allan Wilson Centre for Molecular Ecology and Evolution in New Zealand set out to test the assumption they sanctified authority.

Joseph Watts, lead author of the study, published in Nature, studied the evolutionary family trees of 93 traditional Austronesian societies.

These societies spanned a large range of environments and social structures, from egalitarian societies to complex civil governments.

'Austronesian cultures have been described as a natural laboratory for cross-cultural research due to the diversity of environments they inhabit and cultural features they have evolved,' the study explained.

Human sacrifice was once widespread in Austronesian cultures, across Asia, Oceana and Africa. It was used as the ultimate punishment, for funerals and to consecrate new boats. A study of 93 cultures suggests sacrifices legitimised class-based systems. An illustration of an 18th century sacrifice in Tahiti is shown

The correlation between human sacrifice and high social straification among traditional Austronesian cultures is shown above. Ritualistic killing of humans was practiced in 25 per cent of egalitarian societies studied, 37 per cent of moderately stratified societies and 67 per cent of highly stratified societies

HUMAN SACRIFICE IN AUSTRONESIAN CULTURES Human sacrifice was once widespread throughout traditional Austronesian cultures. 'Common occasions for human sacrifice in these societies included the breach of taboo or custom, the funeral of an important chief, and the consecration of a newly built house or boat,' the study explained. Sacrificial victims were typically of low social status, such as slaves, while instigators were of high social status, such as priests and chiefs. 'The methods of sacrifice included burning, drowning, strangulation, bludgeoning, burial, being crushed under a newly built canoe, being cut to pieces, as well as being rolled off the roof of a house and then decapitated,' the study added. Advertisement

For each culture, the researchers recorded the presence or absence of human sacrifice and coded the level of social hierarchy.

Cultures that lacked inherited differences in wealth and status were labelled as being egalitarian and those with strict hierarchies passed down generations, as having high social stratification.

Analysis revealed evidence of human sacrifice in 43 per cent of cultures sampled.

Ritualistic killing of humans was practiced in 25 per cent of egalitarian societies studied, 37 per cent of moderately stratified societies and 67 per cent of highly stratified societies.

The researchers constructed models to test the co-evolution of human sacrifice and social hierarchy and found that human sacrifice stabilises social hierarchy once the system has arisen.

They said it also promotes a shift to strictly inherited class systems, so that people of a high social class will continue to stay important over time, because of ritualistic killing.

'In Austronesian cultures human sacrifice was used to punish taboo violations, demoralise underclasses, mark class boundaries, and instill fear of social elites - proving a wide range of potential mechanisms for maintaining and building social control,' they wrote.

'In Austronesian cultures human sacrifice was used to punish taboo violations, demoralise underclasses, mark class boundaries, and instill fear of social elites proving a wide range of potential mechanisms for building social control,' the study said. A luakini heiau or human sacrifice temple in Hawaii is shown

'While there are many factors that help build and sustain social stratification, human sacrifice may be a particularly effective means of maintaining and building social control because it minimises the potential of retaliation by eliminating the victim, and shifts the agent believed to be ultimately responsible to the realm of the supernatural.'

Based on their findings, the researchers suggest religious rituals had a darker role in the evolution of modern, complex societies.

'In traditional Austronesian cultures there was substantial religious and political overlap, and ritualised human sacrifice may have been co-opted by elites as a divinely sanctioned means of social control,' the experts wrote.