A situation in which a population suffers a steep decline in numbers owing to some adverse event, such as intensive hunting, habitat destruction, or an environmental disaster. This results in the survival of just a few individuals and consequent inbreeding, with the loss of many genetic variants, or alleles. This reduction in genetic diversity will persist in future generations even if the population recovers. Moreover, small populations are more likely to lose surviving rare alleles through genetic drift. For example, the African cheetah (Acinonys jubatus) experienced such a bottleneck about 12 000 years ago, and the modern population retains a very low level of genetic diversity.