A number of comparisons of nucleotide sequences among hominids and rodents indicate that inbreeding may have occurred more often in hominid than in rodent ancestry. Bakewell et al. (2007. Proc. Nat. Acad. Sci. [USA] 104: 7489-7494) suggest that an ancient population bottleneck that left approximately 10,000 humans might have caused early humans to have a greater chance of genetic disease. Why would a population bottleneck influence the frequency of genetic disease?