As our ancestors began living together in increasing numbers in pre-scientific times, their close proximity created problems that often led to illness and death. Science and technology have overcome many of these. Consider life in early cities. Two thousand years ago, the relatively sophisticated city of Rome used lead pipe to plumb wealthy homes and large waterways. The lead was procured by smelting, the melting and fusion process by which metals are extracted from ore, which produced especially toxic emissions—an early form of humanmade air pollution. Lead was also used in a variety of pottery glazes, in linings for wine containers, and even to whiten the skin in the form of lead acetate. All of these uses caused lead poisoning, symptoms of which can include tiredness, appetite loss, pale skin, changes in behavior, vomiting, stomach pain, headaches, confusion, seizures, weight loss, numbness or tingling in arms or legs, memory loss, and diminished mental development in children.
To verify the problems lead created in ancient Rome, modern researchers have made wine in the way described by period Roman writers, using lead-lined vats and containers. When tested, the resulting wine had very dangerous levels of lead. Likewise, lead in makeup worn by Roman women is known to have leached through the skin and caused poisoning. While lead may not have caused the downfall of Rome, it certainly didn't help. Lead-based paint was used in households in the United States until the middle of the twentieth century, putting children who licked or ate chips of it at risk. Lead was an early additive in gasoline, so it got into the atmosphere and endangered everyone until it was banned in the 1970s. Since science has quantified the dangers of lead in recent decades, its uses have been greatly restricted.
Another example of how population density can lead to severe health problems is associated with the emissions from early heating systems. Prior to the development of heating techniques such as solar, electric, natural gas, and high-efficiency oil furnaces, heating was done primarily by burning wood and coal. Such fuels burn very inefficiently, emit a variety of chemical compounds that cause breathing problems, and deposit grime wherever the smoke settles. As a result, respiratory problems were endemic in cities until the second half of the twentieth century.
Cardiff, Wales was a steel-producing town when I lived there as a graduate student in the 1970s. Vast quantities of coal were used in the smelting process in factories on the outskirts and to heat many of the flats (apartment dwellings) throughout the city. As a result, Cardiffwas perpetually grimy and smelly. One of my good friends, also studying general relativity there, became very ill. For several weeks he could barely function. His mother, a physician, finally diagnosed the problem as carbon monoxide poisoning. It turned out that the coal heater in his flat had developed a leak, allowing the odorless, colorless gas to seep into his bedroom.
Throughout the world, there are still enormous air pollution problems, created in large part by motor vehicle exhaust. The pollution was much worse when gasoline contained lead and exhaust vapors were vented directly into the atmosphere through exhaust pipes. When the hazards of unprocessed emissions were made clear in the 1960s, laws were passed in the United States that banned lead in gasoline and required that exhaust be cleaned before it was emitted. Because the chemistry of the exhaust gases and a large variety of chemical reactions were well understood, scientists and engineers were able to develop catalytic converters that change the gases into less harmful compounds.
Suppose cars had never been developed. If we still used horses to get around, the solid waste and air pollution problems would be stag gering. In the nineteenth century, cities like New York were already ankle-deep in horse manure, and the air contained large amounts of horse-generated methane and other noxious gases. We would have much greater problems than we do with car exhaust if we still used horses for transportation and had to deal with hundreds of millions of them and their "exhaust."
Large groups of people who lived together in cities or other close groups such as armies in prescientific times also died as a result of fast-spreading and devastating diseases. Epidemics were often due to poor sanitation, overcrowding, rodents, and airborne carriers like fleas and mosquitos. Major epidemic diseases included bubonic plague, smallpox, typhus, influenza, whooping cough, diphtheria, dysentery, measles, malaria, yellow fever, scarlet fever, cholera, dengue fever, and polio. The Great Plague of 1665 in London killed over 20 percent of that city's population. Smallpox introduced by European colonizers wiped out over 95 percent of the Native Americans living along the Connecticut River. Likewise, it killed some 200,000 Peruvian natives in the 1520s. Many of these epidemics spread throughout entire countries and continents; when they become pervasive on such large scales they are called pandemics. The 1918 influenza pandemic killed over half a million people worldwide. We are in the middle of an AIDS pandemic as I write this book.
Interestingly, in 1665-66, an epidemic of the plague closed England's Cambridge University and forced Isaac Newton to retreat to his home at Woolsthorpe, in Lincolnshire, England. Sitting out the plague on his own, he developed the mathematical theory of gravitation (Newton's law of gravitation), showed that white light is actually a combination of all the colors of the rainbow (initiating our present understanding of color and optics), and did some of his pioneering work on calculus, thereby helping to jump-start the scientific revolution that eventually helped control many diseases.
Not surprisingly, children have been more susceptible to illnesses we now control than adults. Therefore, infant mortality is used as a measure of how successful medicine has been at preventing and controlling illness. In the 1780s, one writer reported that half the children in Paris died under age 2. At the same time, Thomas Percival, writing in England, noted that half the children born in Manchester, England died before they were 5. By the 1860s, infant mortality ranged from about 14 percent in Sweden to 22 percent in France. Today these countries, along with the rest of Western Europe, have infant mortality rates of less than 1 percent. Science has been crucial in sustaining and improving the quality of life for children and everyone else on the planet.
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