Cheetahs are the most threatened of all Africa’s cats but the reasons lie unexpectedly far back in time, when they came remarkably close to extinction. By studying their enzymes, scientists think that about 10,000 years ago, fewer than seven individuals were left. The cheetahs’ only means of survival was by interbreeding, leaving them with a tiny gene pool.  This lack of genetic diversity has severely weakened them as a species, with low rates of reproduction, poor sperm counts and high rates of infant mortality.