David Peat

176 From Certainty to Uncertaintydiscovered until 1939. At that time DDT held the promise to eradicatethe carriers of malaria, plague, typhus, and yellow fever, as well as protectingcrops from insect destruction. At one stroke the world was giventhe chance to eradicate several deadly diseases and increase food yieldsto the hungry.And what about side effects? Insects are incredibly tiny; thereforewhat is lethal to a mosquito should have no effect on a human being.And so the use of DDT appeared perfectly safe, with the result that itbegan to be used indiscriminately. It was only after more careful researchthat biologists began to suspect that all was not well. To beginwith, insects developed a resistance to the chemical, which meant thatthe doses of pesticide had to be doubled or tripled. Then a more seriousissue emerged. Insects are tiny but they form the diet of fish andbirds. When an enormous number of insects are eaten each day, DDTresidues accumulate in the food chain until they compromise thehealth of higher animals—a famous example was of eggs with shells sofragile that they fractured when the birds attempted to sit on them.The result was that the predators that feed on insects began todie off. Then, because insects breed much faster than birds, within afew generations pesticide-resistant populations of insects bouncedback with a vengeance to occupy an environment lacking in naturalpredators.AntibioticsDuring the first decades of the twentieth century every hospital had aseptic ward for patients in danger of dying from septicemia. By midcentury, such wards had ceased to exist. This medical miracle was dueto penicillin, the first of the antibiotics, developed in commercial formduring World War II. Penicillin revolutionized the treatment of infectiousdiseases to the point that what had previously been life threateningcould easily be cured at home with a course of antibiotics. Inevitablydoctors and hospitals began to rely upon antibiotics as a panaceafor infection.On the face of it antibiotics are one of the great triumphs of modernmedicine. How on earth could there be anything negative to say