Many people feel that human beings should be responsible for the disappearance of some other animal species. It is true we may【M1】______ have hastened the disappearance of some species, but abundant evidence suggests that mankind has actually had few impact Biologists【M2】______ point out that 50 species can be expected to disappear in the 20th century but also remind us that about 50 species became extinct in the 19th century, and 50 species in each of the centuries after that Dr. T. H.【M3】______ Jukes at the University of California has pointed out that about 100 million animal species have become extinct since life began on the earth about 3 billion years before. Thus, animals come and animals【M4】______ go as a consequence of natural selection as Mr. Darwin had invented.【M5】______ The human race is a recent newcomer to the scene, so weve had nothing whatsoever to do with the disappearance of millions of species. In fact, when it comes right down it, were a miserable failure【M6】______ at genocide. In spite of an all-out centuries-old war against rats, but【M7】______ we havent made a dent in its numbers, much less extinguished a【M8】______ single species. And in spite of all our high technology we have not been successful on eliminating a single undesirable insect species!【M9】______ Ive come to the conclusion that the people who are trying to save world are probably quite sincere about it, therefore they dont know【M10】______ much about science and certainly nothing about systems engineering. 【M1】