Routing of nerves and fluid pathways in the human body resembles the tangle of wiring and pipes in an aging house, a heritage from fish and amphibian ancestors. The tube through which sperm passes forms a roundabout loop that can lead to hernias, a result of major anatomical changes that occurred as we evolved from fish. Nerves that are inherited from fish and travel from the brain to the diaphragm can become irritated and trigger hiccups, a closing of the entryway to the windpipe, an action that itself is a hand-me-down from amphibians that breathe with both lungs and gills.