Residue on pottery from an archaeological site has revealed the earliest evidence of beer brewing in China left from a 5,000-year-old recipe, researchers said Monday.

The artefacts show that people of the era had already mastered an “advanced beer brewing technique” that contained elements from East and West, according to a study in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal. Yellowish residue gleaned from pottery funnels and wide-mouthed pots show traces of ingredients that had been fermented together — broomcorn millet, barley, a chewy grain known as Job’s tears, and tubers.

“The discovery of barley is a surprise,” lead author Jiajing Wang of Stanford University told AFP, saying it is the earliest known sign of barley in archaeological materials from China. “This beer recipe indicates a mix of Chinese and Western traditions — barley from the West; millet, Job’s tears and tubers from China.”

The discovery indicates that barley made its way to China some 1,000 years earlier than previously believed. Barley “may have been used as a beer-making ingredient long before it became an agricultural staple,” the study said. The archaeological site at Mijiaya, near a tributary of the Wei River in northern China, includes two pits dating to around 3,400-2,900 BC.