The bodies are only about 350 meters from the Pacific Ocean. More than 140 children and about 200 young lamas or alpacas are laid to rest in the huge burial ground. Archeologists discovered this mass grave last year in northern Peru, near the city of Trujillo. The bodies from the time of the Chimú culture are in a strict, bizarre order: the children look to the west to the sea, the animals, however, to the east to the countryside.

In the journal "PLoS One" reveal the researchers around Gabriel Prieto of the University of Trujillo now the circumstances of human sacrifice - and also the alleged cause.

The Chimú Empire extended to its heyday in the 15th century of today's Lima about 1000 kilometers along the Pacific coast north to the present border of Peru with Ecuador. The people processed metal, farming with sophisticated irrigation systems - Chan Chan, a capital near Trujillo, was one of America's largest cities. In the second half of the 15th century, the empire was conquered by the Incas.

That there were human sacrifices in the Chimú culture was already known. Archaeologists in Chan Chan found in the seventies the remains of hundreds of young women who had apparently been sacrificed at funerals of kings. The present site Huanchaquito-Las Llamas was just outside Chan Chan on the Pacific coast. It was already reported on last year, now follows the scientific work-up.

The incident had begun with a coincidental finding: In 2011, residents had noticed dozens of bones sticking out of the dunes of the area. Archaeologists then found the remains of 137 children, three adults and more than 200 young llamas or alpacas on a 50 by 14 meter area.

The children were boys and girls between the ages of five and 14, the animals were all younger than 18 months, most even younger than nine months. The analyzes indicate that the children were healthy and well-nourished - hence not from poorer backgrounds.

Children from different parts of the Chimú Empire

By analyzing embedded nitrogen and carbon isotopes, the researchers found that the victims came from different parts of the Chimú Empire. The skeletons indicate that the children and the animals had their ribcage opened, presumably to remove the heart. For the adults - two women and one man - that was not the case.

John Verano / DPA

Children of the Chimú Empire - died about 500 years ago

Researchers believe that all victims were killed by a single ritual organized by priests or other ministers. They date the grave to the first half of the 15th century and thus to the late phase of the Chimú Empire, which was conquered in 1470.

El Niño could have caused flooding

According to the researchers, details of the site also reveal the possible reason for the ritual: it is covered by a thick layer of mud, into which the mass grave was embedded. Footprints and hoof prints show that the mud was still wet at the time of the sacrifice.

The researchers suspect that the actually very dry place was hit by heavy rainfall and flooding at that time. This leads them back to the climate phenomenon El Niño, which continues to cause flooding in the coastal region to this day.

"The sacrifice of so many children and camels was a significant investment of resources for the Chimú state," they write. "The temptation to assume that the mass sacrifice of children and camels was an attempt to appease the gods and mitigate the effects of a larger El Niño event that occurred around 1400-1450."

There are reports of child sacrifices from various cultures, many of which are controversial, writes the team. An example of this are the alleged child sacrifices of the Carthaginians in North Africa, which could also be a Roman invention. There are also indications of child sacrifice from Europe, for example in the Ring Shrine of Pömmelte in Saxony-Anhalt, which was created at the transition from the Stone Age to the Bronze Age. However, the researchers are mainly looking for evidence from the New World: also from Tenochtitlan, the Aztec capital, now Mexico City, and the Incas in today's Peru - one knows of sacrifices of children - And just from the Chimú- Culture.