2017届山西省保德县高考英语一轮复习阅读理解基础练：7（含解析）_高考复习指南

2017届山西省保德县高考英语一轮复习阅读理解基础练：7（含解析）

　　Since natural evolution is extremely slow and mankind’s selective production programs only take a few generations to produce a completely new species, natural evolution has already taken a back seat to mankind’s production programs. In addition, mankind has successfully killed off several species all together. For example, there are no more European wolves in existence and mammoths (猛犸象) probably died out because of mankind. Even certain diseases have been permanently got rid of from the planet, and dozens of other diseases will soon be too. Again, natural evolution did i»t cause most of the destruction during man’s rule of the world.

　　Currently, scientists are creating new species with desired characteristics in the lab significantly faster than natural evolution creates new species. In a single generation, new species can be created and destroyed by mankind, while natural evolution could take thousands of years to do the same but only accidentally. Scientists are even able to replace defective (有缺陷的) or damaged genes with different genes to attempt to cure genetic defects. This is something that natural evolution could possibly never correct.

　　Eventually scientists will even be able to improve the quality of people. For example, imagine not only correcting your eyesight with gene treatment, but also ensuring that all of your children do not receive your old genes of poor eyesight too. Scientists will one day be able to improve the memory and intelligence of your children, so that they will do better in school and achieve more in life. Doctors and scientists will be able to customize (订制) babies before they are born just like picking options at a car store.