Archaeologists say they have found a huge cemetery in East Africa that dates back 5,000 years, upending theories on social structure at the time.

It’s thought the Lothagam North Pillar Site, described in a study in the Proceedings of the National Academy of Sciences, was created by some of the earliest herders in Kenya, used to bury men, women, and children.

At least 580 people were buried here, with a large cavity being placed in the center of a platform that’s about 30 meters (100 feet) across to house the bodies. After the bodies were placed inside, the cavity was filled and sealed with stones, before large megalith pillars were placed on top. The cemetery is believed to have been used until about 4,300 years ago.

What’s particularly unusual, however, is that this group of people was thought to have an egalitarian society where people had an equal social status. But such a large construction like this is more indicative of a stratified social hierarchy, one with order and structure.

"This discovery challenges earlier ideas about monumentality," Elizabeth Sawchuk of Stony Brook University and the Max Planck Institute for the Science of Human History, a co-author on the study, said in a statement.

"Absent other evidence, Lothagam North provides an example of monumentality that is not demonstrably linked to the emergence of hierarchy, forcing us to consider other narratives of social change."

Permanent monuments like this are theorized to have been the indicator of a settled society with strong leadership. They may have served as reminders of shared history, ideals, and culture, something that would usually point towards a complex society.

However, none of the people appeared to have been specially treated, and all of them were buried with personal ornaments that were distributed evenly. This, say the researchers, is further evidence for an egalitarian society.

The site is the earliest and largest monumental cemetery found in Eastern Africa. The rocks used to make the pillars were transported from up to a kilometer away, another indication of the mammoth task undertaken to build this cemetery.

One possibility is that it was built for people to come together and converse with each other in tough conditions. An influx of people and farm animals coupled with a decrease in rainfall meant that times were hard, so this may have been a way for people to cope together.

"The monuments may have served as a place for people to congregate, renew social ties, and reinforce community identity," Anneke Janzen, also of the Max Planck Institute for the Science of Human History and a co-author on the study, added in the statement.

"Information exchange and interaction through shared ritual may have helped mobile herders navigate a rapidly changing physical landscape."