Paradoxically, although domestication increases productivity, it also increases instability. This is so because those varieties with the highest yields become the focus of human attention, while other varieties are less valued and ultimately ignored. As a result, farmers become dependent on a rather narrow range of resources, compared to the wide range utilized by food foragers. Today, this range is even narrower. Modern agriculturists rely on a mere dozen species for about 80 percent of the world’s annual tonnage of all crops.22
This dependence upon fewer varieties means that when a crop fails, for whatever reason, farmers have less to fall back on than do food foragers. Furthermore, the likelihood of failure is increased by the common practice of planting crops together in one locality, so that a disease contracted by one plant can easily spread to others. Moreover, by relying on seeds from the most productive plants of a species to establish next year’s crop, farmers favor genetic uniformity over diversity. The result is that if some virus, bacterium, or fungus is able to destroy one plant, it will likely destroy them all. This is what happened in the Irish potato famine of 1845 to 1850, which caused the deaths of about a million people due to hunger and disease and forced another 2 million to abandon their homes and emigrate. The population of Ireland dropped from 8 million before the famine to 5 million afterward.
This concentration of domesticates and the consequent vulnerability to disease intensify with contemporary agribusiness and factory farming. This chapter’s Globalscape examines the role of pig farming in the current swine flu pandemic that began to sweep the world early in 2009.
The Irish potato famine illustrates how the combination of increased productivity and vulnerability may contribute to the geographic spread of farming. Time and time again in the past, population growth, followed by crop failure, has triggered movements of people from one place to another, where they have reestablished their familiar subsistence practices. Once farming came into existence, its spread to neighboring regions through such migrations was more or less guaranteed. From Southwest Asia, for instance, farming spread northwestward eventually to all of Europe, westward to North Africa, and eastward to India. Domesticated variants also spread from China and Southeast Asia westward. Those who brought crops to new locations brought other things as well, including languages, beliefs, and new alleles for human gene pools.
A similar spread occurred from West Africa to the southeast, creating the modern far-reaching distribution of speakers of Bantu languages. Crops including sorghum (so valuable today it is grown in hot, dry areas on all continents), pearl millet, watermelon, black-eyed peas, African yams, oil palms, and kola nuts (source of modern cola drinks) were first domesticated in West Africa but began spreading eastward by 5,000 years ago. Between 2,000 and 3,000 years ago, Bantu speakers with their crops reached the continent’s east coast and a few centuries later reached deep into what is now the country of South Africa. Being well adapted to summer rains, African crops spread no further, for the Cape of South Africa has a Mediterranean climate with winter rains.
World History
