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biochemist at Washington State University. He began by exposing lab rats to a fungicide called vinclozolin, used in vineyards and on fruits and vegetables. He wouldn’t have been surprised to find that exposure to the chemical harmed the rats. But he found much more than that. The fungicide switched on genes in the rats that normally were switched off, and vice versa—and these changes in the operation of the genes were passed on to their offspring. Researchers have known for a long time that chemicals in the environment can alter the operation of genes. But they thought that the genes in sperm and eggs were scrubbed clean of these changes before being passed along at conception. Skinner found that this was not the case. It was quite the opposite—the alterations had become permanent. The flipped switches were passed on to the next generation.
    If exposures to the environment could alter the workings of genes that were once thought to be protected from outside influences, then it made sense to see whether men’s exposures to potentially toxic substances at work could produce harmful alterations in the operation of their genes. Tania A. Desrosiers and colleagues at the University of North Carolina did an epidemiological study in which they looked at large populations of male workers to see whether some jobs were associated with health problems in the men’s children. The hypothesis proved to be correct. Certain occupations of fathers were associated with a greater risk of birth defects in their kids. The riskier occupations included petroleum or gas worker, chemical worker, printer, computer scientist, hairdresser, and motor vehicle operator. Certain jobs were associated with particular birth defects: cataracts and glaucoma were linked to photographers, while digestive abnormalities were linked to landscapers. Epidemiological studies such as this always require confirmation in the lab and clinic, so we can’t yet be sure that this finding is correct. But it’s an important warning sign.
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    These studies represent one unexpected way that fathers and even grandfathers can affect the health of their descendants. But there are other ways to look for connections between fathers and children’s health. One way is to see whether any other paternal attributes contribute to health outcomes in children. Some researchers are trying to find out whether a man’s looks have any consequences for his children. And they are finding provocative answers in, of all animals, zebra finches.
    These birds, native to Australia, are about four inches long. The males have orange cheeks, striped gray-and-white throats, and red beaks. They might seem an unlikely species in which to pursue questions concerning men’s attractiveness. How, for example, would an investigator distinguish a particularly handsome finch from his plainer counterparts? Yet finches have taught us something interesting about fatherhood: the handsomeness of a male makes a difference to his children.
    I heard this story from James P. Curley of Columbia University, an authority on the genetics of fatherhood. He doesn’t work on finches. He works on mice, which are also quite useful in the study of male genetics. But when I went to see him, he told me about the finches and walked me down the hall from his lab to a small room where some of his colleagues kept a noisy population of chattering zebra finches. Genetic tests of these small birds have shown that males can make important contributions to their offspring through an indirect route: by altering mothers’ behavior. Male finches can help their offspring’s chances of survival by making females become more adept at caring for their young.
    The scientists who work with the finches looked at the question of whether the attractiveness of a male affects a female’s parenting behavior. The experiment was prompted by the curious sexual preferences of female finches, which have demonstrated that they prefer males