> What do you do when your diaphragm involuntarily contracts?And the answer: hiccup. Photo credit: Mental FlossAccording to the Mayo Clinic, the diaphragm is "themuscle that separates your chest from your abdomen and plays an important rolein breathing. This involuntary contraction [or reflex] causes your vocal cordsto close very briefly, which produces the characteristic sound of a hiccup."Hiccups can occur from any range of activities – from laughing too much, todrinking too quickly to even just feeling fear. Even fetuses (inside the womb!)can hiccup. But why, exactly?Scientists still aren't exactly sure. What they do know is that the act ofhiccuping is a response which travels along the phrenic nerve up to the brainstem. Once it reaches the brain, it processes the signal and sends one back downto make the diaphragm contract, creating a reflex arc. Hiccups, then, aremomentarily stuck in a signal-response pattern that triggers a contraction ofthe diaphragm involuntarily. To date, there is no known function for hiccups. They don't provide any medicalor physiological advantage; in fact, hiccups actually stop the short intake ofair before it can really reach your lungs. Physiological mechanisms with noapparent purpose such as hiccups create a challenge for scientists. Is there afunction that hasn't yet been discovered, or perhaps none at all? One theoryposits that the act is a relic left over from ancient evolutionary processes,long before humans were around. When creatures in the sea began to evolve toland, their gills became the gradual evolution to lungs (similar to the processof a frog's maturation). As such, the hiccup could have been an inhalation tomove water over the gills but prevent it from filling the lungs. What do you think? Are hiccups an evolved trait, or just a side effect? Learnmore about hiccups below.