Is it possible to imagine a walk through the woods or an excursion to the zoo, during which no living sound fills the air? There is no birdsong, no human voices. Acoustic communication is an integral part of the existence of terrestrial vertebrates, and it is difficult for us to imagine a world shrouded in silence.
However, in the long history of the development of life there were epochs when animals were not yet capable of vocalization. The emergence and evolution of sound communication is the subject of a joint work by paleontologists from the USA and China, published in Nature Communications.
The common ancestor was dumb
Zhuo Chen of Henan Normal University and John Vince of the University of Arizona have studied the history of vocal communication based on evolutionary relationships between land based vertebrates. On a phylogenetic tree spanning the evolution of nearly 1800 species of animals over 350 million years, scientists noted signs of the presence of acoustic communication.
It turned out that the respiratory system of the most distant ancestors of terrestrial tetrapods was not adapted for the production of acoustic signals. The ancestral forms of different groups of modern animals - frogs, crocodiles, birds and mammals - developed vocal abilities independently of each other for a long period from two hundred to one hundred million years ago.
This process, apparently, was unrelated to the rate of speciation. For example, the evolutionary history of groups such as crocodiles and birds lasts more than one hundred million years, and the variety of crocodiles comes down to two and a half dozen species, and there are more than ten thousand species of birds. However, both of them successfully use vocal signals.
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Voice is a means of night communication
How did acoustic communication come about? The authors of the work associated its appearance with forms of daily activity. In the nocturnal way of life, an advantage in the population was given to those animals that could, using sound, draw the attention of a potential partner or, on the contrary, scare off a competitor.
Since those individuals whose respiratory apparatus acquired the ability to vocalize as a result of a complex of mutations multiplied more successfully, the trait useful in night conditions was fixed by selection.
Even in birds, most of which are currently awake during the daytime, traces of nocturnal activity of distant ancestors can be traced. Many species of birds sing before sunrise, when it is still dark, and scientists believe that predawn singing is a legacy of an ancient way of life.
