Mitochondrial mutations may decrease population viability.

It is ironic that an organelle that is pivotal for the function of male gametes is inherited by sons only from their mother. A recent study of human fertility has provided the first definitive evidence that mitochondrial DNA mutations can reduce male fertility but with little or no effect on females. These results present the possibility that the viability of small populations might be reduced by increases in the frequency of mtDNA genotypes that lower the fitness of males.