Archaeological digs have already unearthed many strange secrets of Göbekli Tepe, one of the first temples ever constructed by humans. The discovery of numerous carved human skulls at the Neolithic ritual site in Turkey now suggests it was also the site of the world’s earliest "skull cult”, a group who practiced the ritualistic worship of mutilated human skulls and skeletons.

A German team of researchers has revealed in Science Advances their discovery of three carved skull fragments showing “previously undocumented treatment” of human remains, along with over 400 bone fragments. They think the most likely scenario is that these modifications were made so the skulls could be suspended by a cord.

This is the earliest archaeological evidence of carved skulls for ritualistic purposes. These “skull cults” have been documented throughout the world, including parts of the Pacific, South Asia, the Americas, and other nearby areas of Eurasia. Although it bears some similarities to the practices of the Naga people of India, the style of this modification is unique within the Early Neolithic of Anatolia and the Levant.

Looking at other anthropological evidence for these cultures, the researchers believe the skulls were carved to venerate ancestors not long after their death or to put recently "dispatched" enemies on display. The skulls featured deep cuts down their center (the sagittal axes) and one featured a hole drilled straight through it, along with traces of red ochre pigment. Other minor cut marks on the skulls also suggest they were defleshed.

Various microscopic techniques verified the cuts were intentionally made using flint tools and not from natural causes such as animals gnawing or wear and tear. The researchers also said there were no signs of healing on the bones, indicating the gruesome modifications were probably performed shortly after death. Using the limited amount of bones the researchers had at hand, they conclude that one of the individuals was 25 to 40 years old and likely to be female.

Göbekli Tepe sits in southeastern Turkey, just 50 kilometers (30 miles) north of the Syrian border. It’s believed the site was established around 11,500 years ago and abandoned some 9,000 years ago. The structure is the earliest known example of a human-made building constructed specifically for the ritual requirements. In other words, it's one of the world’s first temples. Previous evidence has also suggested it acted as an early astronomical “observatory”.

Curiously, they still have not actually found any whole bodies buried at the site. There is also no evidence that says people lived at the site. Perhaps then, the researchers say, this means the site was dedicated for the sole purpose of this strange cult.