The Canary and the Bone: A Darwinian Lecture on Erectile Dysfunction

Erectile dysfunction (ED) is one of the most common impairments in sexual function seen in males. The pathogenesis of ED is commonly attributed to a complex interaction of biological, psychological and social factors. The high prevalence of ED and its impact on male sexual function require further explanation from an evolutionary perspective, as one might expect the forces of natural selection to reduce ED frequency over generations. This chapter explores the Darwinian perspective of ED and highlights the importance of sexual selection and the loss of the penile bone, the baculum, as contributing to the presence and persistence of ED in human males. This chapter unravels the complexity of the evolutionary basis of ED, examining the hypothesis that the loss of baculum has generated ED, which serves, like the canary in the coalmine, as an early marker of general health. Thus, the inability to achieve and/or maintain an erection adequate for the fulfillment of sexual intercourse might act as a “fuse” for species preservation. Similarly to how fuses burn in a car to prevent more extensive damage, ED would develop in men who harbor other concurrent conditions, or exposed to accumulation of several risk factors of various origin, as a measure to prevent “damage” to the species as a whole. This mechanism would favor reproduction of healthier men, while at the same time reducing the risk of transmission of harmful genes to subsequent generations. The implications of this hypothesis are explored, as well as the importance of modern medicines targeting the phosphodiesterase 5 enzyme in overcoming the evolutionary handicap of ED.