Looking for a socially acceptable reason to talk about testicles? Want to show off your knowledge of our human evolutionary lineage while you’re at it? Have I got a tidbit for you!
Inguinal (Scrotal) herniation, a condition caused when membranous or intestinal tissue passes through a weak spot in the abdominal wall into the scrotum, serves as an uncomfortable reminder of our fishy evolutionary past. See, fish keep their testicles close to their heart, literally – a biological arrangement that allowed our fish ancestors to keep their reproductive organs safe. As organisms adapted thermal systems suited to life on land, however, the chest cavity simply became too hot for optimal sperm survival rates and the testicles of warm-blooded animals began to take up residence lower in the body plan. By the time the evolutionary tree began producing human fruit, the testicles of most mammals had descended so low that they protruded through the abdominal wall creating the weak spot responsible for inguinal hernias.