The earliest vocal animals probably didn’t use dedicated sound-generating structures, as almost any controllable sounds can be used to communicate, as winner of the award for most unusual vertebrate communication structure, the herring’s fast repetitive tick (FRT). Herring have excellent hearing, although no one ever quite understood why, since they didn’t seem to have any vocal apparatus and were never heard to make sounds. But a study in 2003 showed that large groups of herrings would release bubbles from their anuses that made ultrasonic noises that fit nicely into their hearing range, thus demonstrating communication and social coordination by herring FRTs (and guaranteeing Ben Wilson, lead author on the study, a place in the history books of acronym generation).

— Seth S. Horowitz, The Universal Sense : How Hearing Shapes the Mind, New York: Bloomsbury, 2012.