Cell biologist Keith Campbell, 58, died on Friday at his home in England. Campbell and a colleague were the first scientists to successfully clone a mammal from an adult animal. That mammal was, of course, Dolly the sheep, born in Scotland during the summer of 1996. The experiment proved what many had thought impossible: that cells from an adult animal can produce a viable clone. It also caused controversy and resulted in multiple countries banning the cloning of humans. But why a sheep? Campbell was a pragmatist, saying that "sheep in Scotland are very, very, very cheap."