Study Traces Evolution of Acoustic Communication Back to 350 Million Years Ago

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  Study Traces Evolution of Acoustic Communication Back to 350 Million Years Ago

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• Context - 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.
• Why we started to speak - Acoustic communication among vertebrate animals is such a familiar experience that it seems impossible to imagine a world shrouded in silence. But why did the ability to shout, bark, bellow or moo evolve in the first place? 
• The research - 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.
• How research was conducted - 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. 
• Key Features – 

1. The common ancestor of land-living vertebrates, or tetrapods, did not have the ability to communicate through vocalization. Instead, acoustic communication evolved separately in mammals, birds, frogs and crocodilians in the last 100-200 million years, depending on the group. 
2. 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.
3. The authors estimate that acoustic communication is present in more than two-thirds of terrestrial vertebrates. 
4. Even in lineages that switched over to a diurnal (active by day) lifestyle, the ability to communicate via sound tends to be retained. 
5. Birds kept on using acoustic communication even after becoming diurnal for the most part. Interestingly, many birds sing at dawn, as every birdwatcher can attest. Although speculative, it is possible that this “dawn chorus” behavior might be a remnant of the nocturnal ancestry of birds.
6. The ability to vocalize does not appear to be the driver of diversification — the rate at which a lineage evolves into new species — it has been believed to be. To illustrate this finding, Wiens pointed to birds and crocodilians: Both lineages have acoustic communication and go back roughly 100 million years, but while there are close to 10,000 bird species known, the list of crocodilians doesn’t go past 25..

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