extinction作者提到了克隆人的诸多害处，最后总结，克隆人的后果是人类走向灭亡。

According to Ruth Macklin, cloning should not be banned because "while human cloning might not offer great benefits to human beings, no one has yet made a persuasive case that it would do any real harm either. " But, in my opinion there would be harm. I think Ms. Macklin is too optimistic. Although I am not a pessimist, I am convinced that human cloning should be banned.
    The earth is burdened with a large population thirsty for water, hungry for food, desperate for fresh air and a clean environment. Common sense tells us that we should not increase the world’s population, let alone clone more people. I can’t imagine what the world would be like if scientists are permitted to double or triple today’s population by cloning human beings. In some cases, people support human cloning because they are unwilling to accept death. They want eternal life, we cherish life because it lasts for a short period of time. But we are meant to die. As one famous philosopher said, "we are born to die. " Without death, life is meaningless. If people knew life was endless, perhaps they would have no passion to fulfill their dreams or inspiration to create new things. The world would be full of the same faces. The word "generation" might disappear, as well as "father" and "mother". How boring! The quality of human beings would deteriorate. Brothers, sisters, and cousins would intermarry. Cloned people would have the same father and mother and they would be more likely to have genetic diseases. Cloning, in the long term, might lead to the extinction of the human race. My opposition to cloning doesn’t grow out of an "unthinking disgust". On the contrary, I oppose cloning for practical reasons.