The buculum is a bone present in the head of the penis of most mammals. Whilst a few mammals, like us, don't possess a baculum, some have greatly reduced versions and many have very elaborate shapes. Despite this variety in expression of the baculum, its function remains elusive, though many theories exist. Investigating the function of this bone is Dr Charlotte Brassey, Manchester Metropolitan University, UK, and she joins us for this episode to give us a crash course on penile anatomy and to reveal to us how little we know about genitals.