The evolutionary role of erectile dysfunction

Biologic processes that affect the ability of an organism to reproduce are subject to heavy evolutionary pressure. Erectile dysfunction (ED), a common condition in elderly males, definitely affects the ability of the organism to reproduce, and therefore, it is expected to play a significant evolutionary role. Whereas oogenesis is limited to young females, spermatogenesis is a lifelong process. As a male gets older, the number of (pre-meiotic) mitotic cell divisions during spermatogenesis increases, as does the risk of de novo gene mutations. In this paper, I examine the hypothesis that ED, in addition to decrease in fertility, are two evolutionary safety mechanisms that reduce the probability of an ovum being fertilized with genetically altered sperm from an aged or sick male. This hypothesis is supported by the parallel rise in the occurrence of ED, infertility, and risk of congenital anomalies with age; by the occurrence of these three processes in the same medical conditions; and by the presence of a theory unifying the etiologies of three processes-the "free radical theory of aging". This hypothesis can predict the occurrence of congenital anomalies under conditions associated with ED and infertility but are presently not known to be associated with congenital anomalies.