Abstract
We have compiled a list of several parameters of testicular function and efficiency in an attempt to place human male reproduction in a comparative context. Humans are the worst or next to worst in 13 of 15 measures compared with other well-studied mammals. Low human male fecundity may have emerged as an inevitable trade-off during the evolution of life-cycle trends such as longevity, and may even reflect a long-term trend among the higher Primates. Future research to test this hypothesis should concentrate on critical genes on both the X and Y chromosomes that control testicular function and sperm quality, as well as genes and retroviral elements likely to influence the genetic pathways determining testicular function and male reproductive performance.