THE RETURN OF THE DINOSAURS?
The possibility of cloning fierce and extinct wild animals has always excited film makers.And they are not the only ones！The popularity(受人喜爱)of films such as Jurassic Park，in which a scientist clones several kinds of extinct dinosaurs，proves how the idea struck a mixture of fear and excitement into people's hearts①.But in fact we are a long way from being able to clone extinct animals.Scientists are still experimenting with cloning mammals.This is because the cloning of mammals is still a new science and its story only began seriously in the 1950s as this list shows②：
1950s cloning of frogs
1970s research using the embryos of mice③
1979 work on embryos of sheep and mice
1981 first experimental clones of mice
1983 first experimental clones of cows
1996 first clone of a mammal：Dolly the sheep
2000 cow gave birth to a bison(北美或欧洲野牛)
2001 China's first cloned twin calves(小牛)
2002 first cloned cats
2005 first cloned dog
