Archaeologists with Israel’s Tel Aviv University have discovered a previously-unnoticed geometric pattern in the layout of the excavated portions of Göbekli Tepe, the 13,000-year-old megalithic complex in modern-day Turkey that has upended modern archaeological assumptions since its unveiling over two decades ago. This geometric pattern not only predates the advent of writing and the wheel by at least a millennium, but it also appears to hint at the evolution of human society and consciousness—specifically, the change in our understanding of our place in the natural world.

The discovery of these geometric patterns was made by Tel Aviv University’s Gil Haklay and Avi Gopher, with the architectural pattern apparent in both the internal and external layouts of the three stone circles at Göbekli Tepe known as enclosures B, C and D. An analytical method called “architectural formal analysis” was applied to the complex’s layout by Haklay, an Israel Antiquities Authority archaeologist and a former architect; this form of analysis is used to determine the planning methods and principles used in the design of existing structures.

The analysis was used to determine the center points of each of the three otherwise irregularly-shaped enclosures, each of which sat roughly between the set of twin T-shaped pillars that dominate the center of each circle. While that outcome was expected, one important pattern became apparent: the three points formed a nearly perfect equilateral triangle, with each point only 25 centimeters (9.8 inches) away from forming a perfect triangle with 19.25-meter (63.16-foot) sides.

“I certainly did not expect this,” Haklay said. “The enclosures all have different sizes and shapes so the odds that these center points would form an equilateral triangle by chance are very low.”

Specifically, a line can be traced through enclosure B and C’s four central pillars, forming the southern side of the triangle; a line drawn perpendicularly through the midpoint of this line intersects the triangle’s northern point in the middle of enclosure D, consistent with the geometry of an equilateral triangle.

While such a simple geometric arrangement might be easily taken for granted today, this layout implies that the supposedly hunter-gatherer builders of Göbekli Tepe made a plan of the layout before they commenced construction of the three enclosures, at a time when written language had yet to be invented. The layout would have required the use of a scaled floor plan, according to Haklay, possibly using something as simple as a diagram set out on the ground using reeds cut to equal lengths.

“Each enclosure subsequently went through a long construction history with multiple modifications, but at least in an initial phase they started as a single project,” Haklay explains, referring to the commonly-held assumption that each of Göbekli Tepe’s enclosures were made individually over a long period of time. However, the complex—or at least enclosures B, C and D—appear to have at least been planned as one project, if they weren’t actually built as such. However, if the three circles were constructed at the same time, then even more manpower would be required to build the complex than previously assumed.

“The implication is that a single project at Göbekli Tepe was three times larger than previously thought and required three times as much manpower – a level that is unprecedented in hunter-gatherer societies,” Haklay concludes.

This large-scale coordination of planners and workers (not to mention the people supporting the project with food and other necessities) would make Göbekli Tepe the oldest known example of a stratified society, requiring a hierarchy to successfully plan and execute the project.

The site itself may also indicate that the complex’s builders were aware of such changes to their way of life: Haklay and Gopher suspect that the triangle itself may represent the emergence of a hierarchy in the builders’ society. And while the stonework at Göbekli Tepe is rich with carved reliefs of both humans and animals, the twin pillars at the center of enclosure D are the only ones that depict human figures exclusively, in what may be a powerful message that the humans there began to consider themselves above the natural world.

“In Paleolithic art humans are rare, and this is true here as well, but you start to see change, the beginning of an anthropocentric world view in which animals and plants are no longer equal to humans but are subordinated to them,” according to Gopher.

“The end of the hunter-gatherer lifestyle is more of an ideological transformation than an economic or technological one,” Gopher continues. “Hunter-gatherers cannot domesticate anything; it’s against their world view, which is based on equality and trust. Once that ideology changes, the entire structure of society is transformed and a new world is born.”