Beer was one of the very first drinks humans ever produced – and it may be much older than we previously thought. The brew is generally thought to be about 7,000 years old, but now archaeologists have found clues that could date beer-making to almost twice that age, meaning it predates agriculture and represents the oldest record of man-made alcohol.

The new evidence was uncovered in Raqefet Cave in Israel, which was once a grave site for the Natufian people, hunter-gatherers that populated the Levant region in the Eastern Mediterranean between about 15,000 and 10,000 years ago. On stone mortars found in the cave, Stanford researchers discovered traces of starch and plant particles called phytolith, indicating grains were crushed and processed in a way that suggests beer-making. The find actually surprised the team.

"We did not set out to find alcohol in the stone mortars, but just wanted to investigate what plant foods people may have consumed because very little data was available in the archaeological record," says Li Liu, lead researcher on the study.

According to the team, the beer traces seem to be between 11,700 and 13,700 years old, making them the oldest known evidence of man-made alcohol in the world.

Based on the traces found on the artefacts, as well as an understanding of ancient beer brewing in other areas, the researchers outlined the process that they believe the Natufian people used. First, wheat or barley would be malted by leaving grains in water until they began to sprout, then they would be dried and stored. Later, that malt would be mashed, heated and finally left to ferment with wild yeast.

The end result wouldn't have looked quite like today's beer. According to the team, it would have been thicker, almost like porridge or a thin gruel.

To back up the claims, the Stanford team recreated the ancient recipe, and found that the traces left on their equipment closely matched those found on the artifacts. This isn't the first time the team has brewed beer of this vintage – last year some of the same researchers crafted concoctions based on a 5,000-year-old Chinese recipe, with mixed results.

The find is more significant than just tracing the history of the tradition of a relaxing beer after a hard day's work. The researchers say the brew was likely downed as part of ritual feasts – maybe those celebrating the dead given it was found in a graveyard.

"This discovery indicates that making alcohol was not necessarily a result of agricultural surplus production, but it was developed for ritual purposes and spiritual needs, at least to some extent, prior to agriculture," says Liu.

In fact, not only does the beer apparently predate agriculture, it may have been a motivation for early civilizations to settle down in the first place. The oldest known bread, possibly over 14,000 years old, recently turned up in a Natufian site in Jordan, and together the two may have inspired the population to begin cultivating cereals.

The research was published in the Journal of Archaeological Science: Reports.

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