In 1844, Ireland's population was about eight million. The potato crop that year had been so abundant that there were more potatoes than buyers. The early crop of new potatoes was harvested in August and the second crop, the old potatoes, in October. Between August and May, potatoes were the dietary staple for most of Ireland's inhabitants. The greatest food insecurity occurred during summer, especially for those on the bottom rung of the economic ladder, farm laborers (Ireland's was primarily an agricultural economy). The landowners and larger farmers lived comfortably (the landlords from their rents and the larger farmers from their dairy herds). Farmers were stratified by the amount of land they rented. Even the farm laborers, however, provided they had shelter and enough potatoes, could survive. To pay their rent, some farmers grew cash crops and others kept animals like chickens and pigs. Tenants paid rent...