Peru's Wari Empire likely mixed hallucinogenic seeds with beer to help leaders cement relationships with ordinary people over 1,000 years ago, a study shows.

Researchers have analysed botanical remains of seeds from the vilca tree, used as hallucinogens for thousands of years, that were found in Quilcapampa, Peru.

During communal feasts, hallucinogenic seeds were added to a beer-like fermented drink called chicha made from the molle tree, the analysis indicates, 'to enhance the psychoactive effects of both'. 

Communal drug use reinforced Wari control by both cementing relationships at feasts and making the Wari leadership important as the drug providers, experts say. 

Their study marks the first evidence of consumption of the hallucinogenic vilca tree in the Wari Empire, which ruled the highlands of Peru from AD 600 to 1000, prior to the famous Inca Empire.

Researchers have yet to establish why the Wari Empire collapsed prior to the era of the Incas between the 13th and 16th centuries. 

The study was carried out by researchers at Dickinson College, Carlisle, and University of Rochester, New York in the US, and the Royal Ontario Museum in Canada. 

'This was a turning point in the Andes in terms of politics and use of hallucinogens,' study author Matthew Biwer at Dickinson College told CNN.

'We see this kind of use of hallucinogens as different use context than in prior civilisations, who seem to have closely guarded the use of hallucinogens to a select few, or the latter Inca Empire who emphasised the mass-consumption of beer but did not use psychotropic substances such as vilca at feasts.'