From the living world
Some species evolved from ancestors with external testicles, yet testicles were external, yet the testicles are now inside the abdomen abdomen, as in hedgehogs and dolphins, for example. for example. Why are human testicles located in an eccentric pocket of the body? A question of temperature, seduction by display, to run faster to run faster, or as a result of increased abdominal pressure pressure following bipedalism? As far as living beings are concerned testicles in the inguinal pouch is natural. The thermal makes this practice feasible and accessible.
Knowledge as old as writing.
Heat-dependency for male fertility dates back at least to antiquity. It first appeared in Asia with the practice of hot baths. The thermosensitivity of spermatogenesis was already mentioned in Hippocrates' texts dating back 2,500 years. Thermal contraception has been used throughout the world to this day. It is still difficult to trace its origins, and its qualitative and quantitative developments. The only conclusion we can draw is that it has never been completely forgotten. Even today, in certain contexts, people still use this technique.