Hiccups are found only in mammals

The lung is thought to have evolvedas a structure to allow early fish,many of which lived in warm, stagnant water with little oxygen,to take advantage of the abundant oxygen in the air overhead When descendants of these animals later moved onto land,they moved from gill-based ventilation to air-breathing with lungs.That's similar to the much more rapid changes faced by frogs today as they transition from tadpoles with gills to adults with lungs This hypothesis suggests that the hiccup is a relic of the ancient transitionfrom water to land.An inhalation that could move water over gills followed by a rapid closure of the glottis preventing water from entering the lungs.That's supported by evidence which suggests that the neural patterning involved in generating a hiccup is almost identical to that responsible for respiration in amphibians.Another group of scientists believe that the reflex is retained in us today because it actually provides an important advantage.They point out that true hiccups are found only in mammalsand that they're not retained in birds,lizards, turtles,or any other exclusively air-breathing animals.