Dolly, the most famous sheep since Mary's little lamb, was euthanized on Feb. 14 to prevent further suffering after she acquired a severe lung infection. The sheep, which was 6 years old, was the first mammal to be cloned from the DNA of an adult, and its birth set the stage for the current furor over human cloning (SN: 4/5/97, p. 214: http://www.sciencenews.org/sn_arc97/4_5_97/bob1.htm; 10/20/01, p. 250: Dolly Was Lucky).
For most of her life, Dolly was as healthy as a typical sheep, although many other mammalian clones have had severe, if not fatal, physical defects. While there was speculation that Dolly was aging prematurely because the tips of her chromosomes appeared shorter than normal for a sheep her age, her creators at the Roslin Institute in Edinburgh say there is no definitive evidence of such a problem.
Domestic sheep can live up to a dozen years, but it's not unusual for sheep kept in stalls to contract infections and die young,