abstract
Inbreeding, which can lead to the loss of genetic variation or the accumulation of deleterious alleles, has been shown to reduce fitness in wild1, zoo, laboratory2 and farmed3 animals. But it has been proposed that when combined with selection, inbreeding may purge deleterious alleles4. Here we provide support for this hypothesis in a study of the Chillingham cattle, which shows that this viable herd is almost genetically uniform. The homozygosity of this herd far exceeds that of other cattle5 and that found in wild populations of other mammalian species6, 7.