Today’s mild, widely popular lettuces, varieties of the species Lactuca sativa, derive from an inedibly bitter weedy ancestor, L. serriola, that grew in Asia and the Mediterranean and has been under cultivation and improvement for 5,000 years. Lettuce seems to be represented in some ancient Egyptian art, and was certainly enjoyed by the Greeks and by the Romans, who had several varieties and ate them cooked as well as raw in salads at the beginning or end of the meal. The first syllable of its Latin name, lac, means “milk,” and refers to the defensive white latex that oozes from the freshly cut base. Though lettuce is now mostly eaten raw in the West, in Asia it’s often shredded and cooked. This can be a good use for the older, tougher leaves sometimes found on supermarket lettuces.