Cheetahs are not a healthy species. Several million years ago they were widespread in Africa and Asia, but their numbers fell drastically during the last ice age and again when they were hunted to near extinction in the nineteenth century. Now, they suffer from low survivorship (a large number of animals dying), poor sperm quality, and greater susceptibility to disease. Normally, an animal will reject tissue transplanted from another animal, but cheetahs will not reject tissue grafted on to them from another cheetah. What happened to the cheetah? How did their genetic variation change? Where does genetic variation ultimately come from? What mechanism can maintain and increase genetic variation in natural populations