When and why vertebrates learned to make sounds

When and why vertebrates learned to make sounds
When and why vertebrates learned to make sounds

Wildlife is full of various sounds - from birdsong and frogs croaking to lion's roar and hyenas "laughing". Vocalization helps animals avoid danger, attract partners, and interact in a group.

But what was the root cause of acoustic communication and how did it develop?

The answers are provided by a new study by scientists from the United States and China. They studied the evolution of the vocalization of vertebrates living on land.

The authors created an evolutionary tree of 1,800 species of mammals, birds, reptiles and amphibians and tracked their relationships over 350 million years.

From the scientific literature, the researchers obtained data on the absence or presence of acoustic communication in each species and noted this on the created tree.

Using statistical analytical tools, the scientists tested whether acoustic communication arose independently in different groups (and if so, when), whether it was associated with nocturnal activity, and whether vocalization persisted in one or another "pedigree".

As a result, it turned out that the ancestors of terrestrial vertebrates did not use the respiratory system to produce sounds, that is, they did not have the ability to communicate through vocalization.

Instead, it turned out that acoustic communication has evolved independently in different terrestrial vertebrates over the past 100-200 million years (depending on the group).

In addition, research has shown that the origin of vocalization is closely related to the nocturnal lifestyle.

It is logical that in the absence of light, animals could not exchange any visual signals to intimidate a competitor, attract a partner, or other purposes. Therefore, acoustic communication has brought many benefits to nocturnal vertebrates.


Perhaps acoustic communication is a more stable evolutionary trait than other types of signaling, such as coloration.

Photo by Global Look Press.

Based on their analysis, the authors also concluded that acoustic communication is present in more than two-thirds of terrestrial vertebrates. And this is not only the familiar chirping of birds or the croaking of frogs. Crocodiles and some turtles also have "vocal abilities."

It is also interesting that many animals that "emerged from the twilight" and today lead a diurnal lifestyle have retained sound communication.

"There is an advantage in developing acoustic communication when you are active at night. But it does not become a disadvantage when switching to daytime activity," says co-author John Wiens of the University of Arizona. "We have examples of how acoustic communication is preserved in frogs and mammals which became active during the day, although hundreds of millions of years ago were nocturnal."

Another vivid example is birds, which also did not abandon vocalization. Moreover, they usually sing at dawn, which can (in general, speculatively) be considered a consequence of the nocturnal lifestyle that took place hundreds of millions of years ago, the researchers say.

They also believe that acoustic communication is a remarkably robust evolutionary trait - more robust than other types of signaling, such as coloration, for example.

In addition, the analysis showed that vocalization ability is not the driving force behind diversification. That is, it did not affect the rate of appearance and development of new species of vertebrates.

To illustrate this unexpected conclusion, Vince uses the example of birds and crocodiles. Both lines have acoustic communication, and their evolutionary history has been going on for a hundred million years. But if the birds have about ten thousand species, then the detachment of crocodiles is only 25.

Another example: scientists know about ten thousand species of lizards and snakes, most of which do without vocalization. Meanwhile, mammals have about six thousand species, and 95% of them communicate through sounds.

“If you look at it on a smaller scale, like a few million years ago and within certain groups like frogs and birds, the idea that acoustic communication leads to speciation works. But we looked at 350 million years of evolution., and acoustic communication [in this case] does not explain the patterns of species diversity that we see, "- said John Vince.

More details about this work are described in an article presented in the journal Nature Communications.