The turkey that graces most American tables for Thanksgiving and throughout the year is known as the broad-breasted white. It's a modern strain born of generations of breeding to be a fast-growing, fat-breasted, easy-to-raise butcher bird that is physically unable to reproduce — every white-breasted turkey born is a result of in vitro fertilization or artificial insemination. Modern-day factory turkey farms are crowded, dirty places in which birds are fed antibiotics to stay alive. If an especially virulent strain of bird flu or another disease were to evolve, it could quickly spread through the nation's turkey farms — and we'd find ourselves returning to the Pilgrim habit of eating eel for Thanksgiving.