Understanding the evolution and function of structures in the past is key to understanding current biodiversity. This paper shows how an evolutionary perspective can help us to understand supracondylar syndrome. This pathology is caused by compression of the median nerve and/or the brachial artery in the arm and affects a significant percentage of the human population. We propose that this neuropathy is an atavism (the reappearance of an ancestral characteristic that had been lost along our evolutionary lineage) of the entepicondylar foramen: a channel present at the lower end of the humerus through which the brachial artery and the median nerve pass in some mammals. The origin of the foramen has been identified in the first tetrapods, and we propose that its original function could be linked to the evolutionary innovation of the cervical brachial plexus as well as the subsequent evolution of the entepicondylar foramen in amniotes ??a group of terrestrial vertebrates that encompasses current reptiles and amphibians?? and that it may be vestigial.