'World's oldest calendar' discovered carved into ancient monument

A devastating ancient comet strike in Turkey appears to be etched into what may be the world's oldest lunisolar calendar, assuming the event happened in the first place.

Archaeologists recently reinterpreted markings on a stone pillar at Göbekli Tepe in southern Turkey, the site of one of the world's oldest ancient farming communities. The Mesopotamian site is roughly 12,000 years old, dating to the beginning of the Holocene that marks the most recent epoch of Earth since the glaciers retreated.

"Ancient people may have created these carvings at Göbekli Tepe to record the date a swarm of comet fragments hit Earth nearly 13,000 years ago — or 10,850 BCE," the University of Edinburgh in Scotland said Tuesday (Aug. 6) in a statement .

The research is led by the university's Martin Sweatman, who has published before on the infamous comet event that is said to have kickstarted agriculture , among other knock-on effects on ancient Earth. But not everyone agrees the comet strike happened.

Related: Did a comet strike 13,000 years ago change human civilization as we know it?

Sweatman's research includes chemical engineering and statistical mechanics as well as studies in archaeoastronomy. His team's work made headlines in 2021 when they suggested a comet slammed into our planet 13,000 years ago based on finding a lot of platinum in sites of North America and Greenland. (Platinum can be formed in areas of high temperatures, including in the case of meteor strikes.)

The theory of the comet strike event, called the Younger Dryas impact hypothesis, dates back to a 2007 peer-reviewed paper in the Proceedings of the National Academy of Sciences led by nuclear physicist Richard Firestone, according to the New York Times Magazine . The theory remains debated by specialists to this day, some of whom say (for example) that the findings could account for a rapidly cooling climate that was not necessarily sparked by a comet fall.

Sweatman's 2021 paper said these counterarguments were from a "small cohort of researchers" whose claims are "poorly constructed." Yet the debate is in fact fairly wide-ranging and mainstream, according to a 2018 report in Science News , as experts continue to examine aspects such as why there is no suspect crater linked to the Younger Dryas impact, and what remnants the comet may have left behind.

Related: 40 years ago, a comet came out of the blue in a surprise Earth flyby. Here's what we know now.

Assuming the comet impact was true, Sweatman's group says they re-examined a set of V-shaped symbols carved across several pillars at Göbekli Tepe. Their work suggests that if each V was a single day, the community accurately marked the 365-day solar calendar.

Adding credence to this theory is a special entry for the summer solstice, "represented by a V worn around the neck of a bird-like beast thought to represent the summer solstice constellation at the time," the researchers wrote in the University of Edinburgh release. "Other statues nearby, possibly representing deities, have been found with similar V-markings at their necks."

Additionally, two enclosures (labeled C and D in the study) are made up of 11 T-shaped pillars. When interpreted alongside other archaeological sites in the region that gave special significance to the number 11, the study team says this is evidence that the inhabitants of Göbekli Tepe were also tracking the 11 full phases of the moon in a 365-day solar year.

As for the comet strike, the team says the evidence for that lies on what they call Pillar 18, located in Enclosure D. The pillar is a person-like or anthropomorphic shape that has a horizontal "head" and a vertical "body", according to the peer-reviewed study in Time and Mind . Also visible on the pillar is a belt buckle and fox-pelt loincloth that is drawn in the possible shape of a comet, the researchers say.

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The possible comet shape on Pillar 18 may be reminiscent to that of the Nebra sky-disk, a second millennium BCE artifact unearthed in modern-day Germany, the study team argues. The disk shows the moon, sky, a grouping of stars that could be interpreted as the Pleiades and (perhaps most contentiously) a comet.

The comet, if it is indeed on the disc, is represented by a "long, curved shape incised with parallel lines," the Göbekli Tepe team writes.

But the comet hypothesis is not fully agreed upon by researchers of Nebra; others have suggested it depicts a mythological boat or a rainbow, Astronomy Magazine wrote in 2021 . Or the shape may be an aurora borealis , according to a short report in Physics Today that same year .