Sometime in the early 1990s, Claudio Grossi, a 40-year-old farmer in Parma, in northern Italy, was cleaning his attic when he turned up an old sack full of seeds that he couldn’t identify. The bag, he was sure, had been left by his late great-grandfather, who’d started the farmstead around 1915. Grossi had no idea how long the seeds had been sitting there, deprived of water, soil and sun. Dry ...