John Conway, an Irishman, was at work in a bog when he made an interesting discovery recently: a 22-pound lump of ancient “bog butter,” sunk into the depths of peat, likely from about 2,000 years ago. Though it sounds surprising to Americans, finding a clump of dairy fat in a bog is fairly commonplace, with 430 instances currently on record. The butter can be as old as the Iron Age—roughly 600 B.C.—or as recently as the 1600s. Even today, the stuff retains a buttery smell—a chef who tasted an ancient specimen said “it goes right up your nose;” a modern variation produced by the Nordic Food Lab in 2012 drew reviews ranging from “animal” to “salami.

So