A study tracing acoustic communication across the tree of life of land-living vertebrates reveals that the ability to vocalize goes back hundreds of millions of years, is associated with a nocturnal lifestyle and has remained stable. Surprisingly, acoustic communication does not seem to drive the formation of new species across vertebrates.

But why did the ability to shout, bark, bellow or moo evolve in the first place? In what is likely the first study to trace the evolution of acoustic communication across terrestrial vertebrates, John J. Wiens of the University of Arizona and Zhuo Chen, a visiting scientist from Henan Normal University in Xinxiang, China, traced the evolution of acoustic communication in terrestrial vertebrates back to 350 million years ago.

The authors assembled an evolutionary tree for 1,800 species showing the evolutionary relationships of mammals, birds, lizards and snakes, turtles, crocodilians, and amphibians going back 350 million years. They obtained data from the scientific literature on the absence and presence of acoustic communication within each sampled species and mapped it onto the tree. Applying statistical analytical tools, they tested whether acoustic communication arose independently in different groups and when; whether it is associated with nocturnal activity; and whether it tends to be preserved in a lineage.

The study, published in the open-access journal Nature Communications, revealed that the common ancestor of land-living vertebrates, or tetrapods, did not have the ability to communicate through vocalization — in other words, using their respiratory system to generate sound as opposed to making noise in other ways, such as clapping hands or banging objects together. Instead, acoustic communication evolved separately in mammals, birds, frogs and crocodilians in the last 100-200 million years, depending on the group. The study also found that the origins of communication by sound are strongly associated with a nocturnal lifestyle.

This makes intuitive sense because once light is no longer available to show off visual cues such as color patterns to intimidate a competitor or attract a mate, transmitting signals by sound becomes an advantage.

Extrapolating from the species in the sample, the authors estimate that acoustic communication is present in more than two-thirds of terrestrial vertebrates. While some of the animal groups readily come to mind for their vocal talents — think birds, frogs and mammals — crocodilians as well as a few turtles and tortoises have the ability to vocalize.

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Materials provided by University of Arizona. Original written by Daniel Stolte. Note: Content may be edited for style and length.