阅读理解,阅读下列短文,从每题所给的四个选项(A、B、C、D)中,选出最佳选项。
Just about every week now, we read a newspaper headline about the genetic basis for breast cancer, intelligence, or obesity.Such news stories may lead us to believe our lives are being revolutionized by genetic discoveries.We may be close to changing and getting rid of mental illness, for example and identify the causes of crime, personality, and other basic human weaknesses.
But these hopes, it turns out, are based on faulty assumptions about genes and behavior.
In many cases, people are motivated to accept research claims by the hope of finding solutions for frightening problems, like breast cancer.Accepting genetic causes for their characteristics can relieve guilt about behavior they want to change but can't.Efforts made to fight against them, at growing expense, have made little or no visible progress.The public wants to hear that science can help.
Meanwhile, genetic claims are being made for many ordinary and abnormal behaviors, from addiction to shyness and even to political views and divorce.If who we are is determined from pregnancy, then our efforts to change or to influence our children may be useless.There may also be no basis for insisting that people behave themselves and obey laws.Thus, the revolution in thinking about genes has great consequences for how we view ourselves as human beings.
Most claims linking emotional disorders and behaviors to genes are statistical in nature.The research finds are insufficient for deciding that alcoholism or mainic-depression(躁狂抑郁症患者)is inherited.In the late 1980s, genes for manic-depression were identified by teams of geneticists.The claims have now been definitively proved wrong.
Genetic data on the major mental illnesses make it clear that they can't be reduced to purely genetic causes.According to Myrna Weissman, Ph.D., Americans born before 1905 had a 1 percent rate of depression by age 75.Among Americans born a half century later, 6 percent become depressed by age 24! Similarly, while the average age at which manic-depression first appears was 32 in the mid 1960s, its average beginning today is 19.Only social factors can produce such large shifts in rate and age of beginning of mental disorders in a few decades.
Scientists actively debate whether disorders like alcoholism are more or less biologically driven.If they are mainly biological-rather than psychological, social, and cultural-then there may be a genetic basis for them.In 1990, Kenneth Blum, Ph.D., of the University of Texas, and Ernest Noble, M.D., of the University of California, Los Angeles, found a certain gene in 70 percent of a group of alcoholics, but in only 20 percent of a non-alcoholic group.But in 1993 Joel Gelernter, M.D., of Yale and his colleagues surveyed all the studies that examined this gene and alcoholism.Different from Blum and Noble's research, the results were that 18 percent of non-alcoholics, 18 percent of problem drinkers, and 18 percent of severe alcoholics all had the gene.As for Blum and Noble's work, a more reasonable model is that genes may affect how people experience alcohol.Perhaps some people's nerves are more activated by alcohol.But although genes can influence reactions to alcohol, they cannot explain why some people continue drinking to the point of destroying their lives.
Therefore, claims that our genes cause our problems, our misbehavior, even our personalities are more a mirror of our culture's attitudes than a window for human understanding and change.
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