Now this is recipe I hope to see in next year's Marin County Fair! We'll, there isn't really much of a recipe but an ingredient list. I appreciate the hypothesis of the sweetening of the brew to balance the sourness that was likely present. Perhaps the sours of today needn't be so dry?
http://www.nationalgeographic.com/people-and-culture/food/the-plate/2016/05/5000-Year-Old-Microbrewery-Found-In-China/