Recent data from molecular genetics and epidemiology provide evidence that paternal age (sperm quality) is an important risk factor for offspring. When the sperm quality of young men were compared with the sperm of older men, the latter were found to have a higher risk of suffering genomic mutations in their sperm, which may be the reason for the increasing incidence of genetic diseases in western society, where fatherhood is increasingly delayed (Journal of Medical Ethics 41; 775-779, 2015).