Responsibility 2: the individual

The health of human beings is determined by their behavior, their food, and the nature of their environment. The first agricultural revolution occurred 10,000 years ago with the domestication of plants and animals. Nomadic hunter-gatherers settled around their flocks and fields. Nutrition improved, with a resultant fall in mortality and rise in birth rates. The population expanded, but its growth was checked peri odically by crop failures and famine, tribal war over scarce resources, infectious disease now easily transmitted by air, water, and food among settled people, and the common practice of infanticide. The population was under 10 million people. By 1750, the number of people in the world had grown to 750 million, by 1830 to one billion, by 1930 to two billion, by 1960 to three billion, and then to four billion today. This massive growth of population resulted from the fall in mortality rates attendant upon steadily increasing food supplies. Improved nutrition again increased birth rates and resistance to infectious disease. The greater availability of food also reduced the practice of infanticide. The second agricultural revolution had begun in the eighteenth century; it included increased land use, extensive manuring to restore soil fertility, crop rota tion, winter feeding, and the widespread cultivation of potatoes and maize. A mas sive increase in available food was extended still further by the Industrial of the nineteenth and twentieth centuries through mechanization, extensive irriga tion, chemical fertilizers, and pesticides. The Green Revolution of the past thirty years further increased food production, and was based on genetic manipulations which produced hardier and more productive varieties of crops, responsive to the more intensive use of water and fertilizer. More than half the reduction in mortality rates over the past three centuries occurred before 1900 and was due in nearly equal measure to improved nutrition and reduced exposure to air-and water-borne infection. The provision of safe water and milk supplies, the improvement in both personal and food hygiene, and the efficient disposal of sewage all helped to reduce the incidence of infectious disease. Vaccination further reduced mortality rates from smallpox in the nineteenth century and from diphtheria, pertussis, tetanus, poliomyelitis, measles, and tuberculosis in the twentieth century, although the contribution of vaccinations to the overall reduction in mortality rates over the past hundred years is small (perhaps as small as 10 per cent) as contrasted with that due to improved nutrition and reduction in the transmission of infectious disease.1 An even smaller contribution has been made by