Who is the first animal in the world to make active sounds? When life began to chirp

Author: Global Science

We are used to the fact that the Earth is filled with animal sounds, but it is an interesting fact that for most of the Earth's history, there were only sounds like wind, rain, and waves, but no active sounds made by animals.

Although the earliest known life was 3.7 billion years ago, early life was in the form of microorganisms. Even though some multicellular mollusks appeared much later, you obviously can't ask a jelly to make a sound.

It wasn’t until about 500 million years ago, after the Cambrian explosion, that animals began to have some basic vocalizations, but they were just the sounds of limbs rubbing against the environment. For example, the sound of arthropods’ feet scraping across the sand, or the friction of cephalopods poking out of their shells. Including the oldest known insects, which appeared about 400 million years ago, they probably couldn’t make any sounds, or even hear them. At the same time, there were basically no sounds made by animals on land. It was more than 200 million years later that buzzing insects appeared, creating a whole new world of acoustics.

Insect eardrum

In fact, the oldest known insects can be traced back to 400 million years ago, but they are likely not only silent, but also deaf. In order to track down the earliest insects that can make sounds, scientists from the Nanjing Institute of Geology and Paleontology studied a large number of insect fossil specimens collected from museums around the world, and then they focused all their attention on an Orthoptera insect called katydid.

Katydids, commonly known as katydids, can make sounds by rubbing their front wings together, and receive sound signals through the eardrums of their front feet. Katydids were very abundant in the Mesozoic Era, making them an ideal species for studying the evolution of animal acoustics.

Based on a large number of studies, scientists have established a database of key morphological features of katydid fossils and systematically reconstructed the frequency of the chirping of Mesozoic katydids. In an article published in 2022, they speculated that as early as the middle of the Triassic period 240 million years ago, katydids could already make high-frequency chirps, that is, 12kHz-16kHz. This is also the oldest record of high-frequency sounds in the entire animal kingdom. Katydids were very prosperous during the Mesozoic Era. They were like tireless "singers" who sang from early morning to night. In the chirping sounds that came one after another, they declared their territory, sought relatives and friends, and courted and reproduced.

In addition, the earliest known cicada fossils can also be traced back to this period. These insects can produce particularly loud sounds by quickly tensing and relaxing the eardrum in the drum-like structure of the abdomen. In some insect fossils, the sound-producing structure is well preserved, allowing researchers to restore the songs they "sang" at the time.

For these earliest examples of buzzing insects, being able to make and hear sounds had many benefits. They could use sound to communicate over long distances, hear nearby predators, and even lure prey by mimicking the sounds of potential mates. Sound also provided a new way to attract mates, giving rise to a new biological struggle - which creature could make the loudest noise.

Around the same time that insects began buzzing and chirping, vertebrates also began experimenting with making several types of sounds.

Dinosaur throat

Around the same time that insects began to squeak and buzz, vertebrates also evolved a very important structure for making sounds - a structure we still use today: the larynx.

In fact, it is difficult to know exactly how the larynx first appeared. Because the larynx is made of cartilage, but cartilage is usually difficult to preserve as fossils. However, some studies have suggested that the larynx may have appeared at the same time as terrestrial vertebrates, about 300 million years ago.

By the Mesozoic Era, vertebrates had developed a variety of vocalization abilities. If you were to pick a group of animals with the most fancy vocalization skills during this period, it would be the dinosaurs.

Mesozoic dinosaurs evolved into a rich group, each of which has its own unique vocalization skills. For example, Parasaurolophus, a herbivorous dinosaur belonging to the hadrosaur family, has a huge crest on its head. In 1981, paleontologist David Weisham discovered that this crest is vacuum-filled like a trumpet and is connected to its respiratory tract, so he believed that this crest is actually a resonance chamber that can enhance the sound produced by Parasaurolophus. (This is real head cavity resonance)

Other researchers have found that the skulls of many dinosaurs are not solid, but have many complex holes. They suggest that when air flows through such skulls, it can not only regulate the body temperature of dinosaurs, but also make them make various sounds.

Of course, when we talk about dinosaurs, we have to mention movies and TV shows like Jurassic Park, which often give dinosaurs a very loud roar (Ouch). However, this is not consistent with the fossil evidence we have found.

Some studies have suggested that, based on the fossil evidence found so far, the calls of theropod dinosaurs such as Tyrannosaurus Rex may be more like birds than mammals. In other words, Tyrannosaurus Rex was actually "crying" rather than "roaring."

But it's not like the T. rex quacked like a giant goose, or chirped like a giant sparrow, but "chirped" in a biomechanical sense. It sounded more like a humming sound that started from vibrations deep in the chest, with the mouth closed, and emitted through the nose.

Then there are the big dinosaurs—the sauropods with long necks and huge bodies. Some movies like to make Brachiosaurus and Diplodocus make sounds like elephants, but in reality, they probably made almost no sound, and at most could only make a hissing sound. There is a problem here. All of us quadrupeds, from frogs to humans, use the larynx to make sounds, which are controlled by the recurrent laryngeal nerve. This nerve has a strange route: it goes down the neck, around the chest, and then back up the neck to the larynx. In other words, the nerve signal for sound needs to travel a distance twice the length of the neck.

For the length of our human neck, twice the length of the neck is nothing. But imagine that this route, for a Brachiosaurus with a neck several meters long, will bring serious signal delay. It is hard for us to imagine how they can control the rapid movement of the vocal cords to make complex sounds such as chirping or roaring with such delay.

Bird's syrinx

There is a type of dinosaur that has evolved a very unique vocal organ, and that is birds. Although there are too obvious differences in appearance, birds did evolve from saurischian theropod dinosaurs. When they evolved into agile creatures and flew in the sky, the unique singing of birds also became their very unique symbol.

The vocal organs of birds are completely different from those of reptiles and mammals. Birds use the syrinx to make beautiful calls. The syrinx is located at the junction of the trachea and bronchi of birds, and is placed at the bifurcation of the respiratory tract like a "human" shape. Usually, the syrinx is composed of a part of the tracheal wall (the syrinx) and the semilunar membrane in the middle. In addition, there are syrinx muscles on the outside of the tracheal wall that can control the movement of the trachea.

When air flows through the syrinx, it causes the syrinx and the semilunar membrane to vibrate, thus producing sound. The syrinx muscle can only adjust the details of the sound by changing the tension of the syrinx and the bronchial opening. It can be said that the vocalization process of birds involves the generation and resonance of sound. The air flows through the syrinx, causing the syrinx to vibrate and produce sound. The syrinx produces different types of harmonics under the regulation of the syrinx muscle.

It is worth noting that the syrinx is located where the trachea bifurcates, and this structure allows the left and right syrinx muscles to control vibrations relatively independently. Therefore, some songbirds can not only make chirping sounds when exhaling and inhaling, but also sing alone or in a coordinated manner. This method has greatly expanded the sounds that songbirds can make.

As to how this sophisticated structure evolved, it is also a very interesting scientific question.

We know that to understand the history of evolution, the most important research material is fossil evidence. Generally speaking, only relatively hard bones and shells are more likely to withstand the test of time and remain as fossils. Therefore, for a long time, scientists believed that soft tissues such as syrinxes were difficult to preserve as fossils, so it was difficult to describe their evolution process.

But in 2016, everything changed when scientists used high-resolution tomography to analyze a fossil. The fossil was found on Vega Island, east of the Antarctic Peninsula in Antarctica. So scientists named it Vega bird. Vega bird can be traced back to 66 million to 68 million years ago, which is equivalent to the Late Cretaceous. When the fossil was first discovered, scientists had already done some restoration work and found that it was a flying bird very similar to the current wild geese, but it may not be the direct ancestor of today's wild geese.

In a high-resolution tomography scan conducted in 2016, scientists unexpectedly discovered that the junction between the trachea and bronchus of Vega bird was significantly enlarged, and there were also large gaps between the bronchial cartilages. This feature is very similar to today's syrinx. It can be said that this also suggests that Vega bird at that time had evolved a syrinx that can make sounds. Further research shows that Vega bird may be able to make sounds like today's geese or ducks. Not so gentle and moving, but it also adds new fun.

From the first appearance of birds 150 million years ago to the appearance of the earliest known syrinx 68 million years ago, birds have had a very interesting experience in this process. Because the larynx is already a vocal organ, they still found a way to re-evolve a new vocal organ in another part of the organ. This is rare in the history of evolution. Today, birds still retain their larynx, but except for a few birds, almost no birds use the larynx to make sounds.

It is worth mentioning that although pterosaurs also occupied the ecological niche in the sky at that time, this creature was not actually a bird, and its way of making sounds was also different from that of birds.

The emergence of echolocation

Vocalization and hearing have evolved to have more functions besides communication. We all know that bats and whales have the ability to "see" things with sound, which is echolocation. Echolocation requires the evolution of many organ physiological structures to complete.

The resolution of objects that can be seen by echolocation is inversely proportional to the wavelength of the sound emitted. If bats want to use sound to detect small targets such as insects, they have to emit sounds with very short wavelengths, that is, higher frequencies.

For comparison, the upper limit of human hearing is about 20,000 Hz, while the frequency of the sound produced by bats with their larynx and tongue can range from 15,000 to 200,000 Hz. The sharp squeaking sound we hear is only in the low frequency range for bats.

Likewise, bats have evolved enormous inner ear structures to hear ultrasonic echoes: The human cochlea is smaller than a dime, but a bat's cochlea (if enlarged to the same size) can be as big as a golf ball.

Echolocation can also be used in underwater environments. And because the attenuation of sound in water is much smaller than in air, echolocation in water can see objects farther away than in air. Bats in the air may not be able to locate large objects 50-90 meters away, and if it is a small insect, the distance must be even closer. But some dolphins can distinguish objects 200 meters away through echolocation.

Underwater environments are conducive to transmitting sound as far as possible, and large aquatic animals have a natural advantage in this regard. For example, the huge baleen whales have a larynx that is about 60 centimeters long and can produce sounds at extremely low frequencies that are inaudible to humans. The sounds of some baleen whales can be transmitted hundreds or even thousands of kilometers away.

Unfortunately, human activities in the ocean can sometimes be too noisy. Many creatures in the ocean rely on making and hearing sounds to communicate, track prey, and find mates. However, the noise from humans can easily drown out the sounds made by these marine creatures, seriously affecting their survival.

The emergence of human language

About 230 million years after the sounds of early mammals began to spread across the world, vocalization began to play a new role in the evolution of human language. The structural prerequisites for language include a larynx that can adjust rapidly and a closely connected larynx and tongue. These structures can be traced back to at least the origin of our own species, the early genus Homo. This means that our ancestors may have had some form of language as early as 2.8 million years ago.

However, when and where the earliest human language originated is still a controversial issue. Language requires not only structures that can make sounds, but also the ability of humans to understand the world with tools such as symbols and images, that is, symbolic thinking. Most models indicate that Homo erectus, which debuted about 1.8 million years ago, was the first human ancestor to use symbols. But fully formed human language and its complex grammatical and syntactic rules may be unique to Homo sapiens, which also means that the origin of human language can only be traced back to a few hundred thousand years ago.

Humans not only have powerful languages, but also unique abilities to teach, learn, and record them. Interestingly, it seems that as humans became accustomed to the changes in voice and intonation, they gradually evolved singing. This form not only further enriches the soundscape of the world, but also allows humans to express their feelings or strengthen the cohesion of the group. In primitive tribes, many important activities are accompanied by unique songs and dances. Even in modern times, singing is still one of the most important cultural activities in human society.

Human language is arguably one of the most influential traits ever evolved. Our societies and civilizations are built on language. It’s through language that we collaborate and invent technologies from agriculture to the space shuttle, which themselves have contributed to the modern soundscape. While our voice isn’t the first animal sound, nor the loudest or sweetest, it’s in some ways the most profound transformation of the world.

This article is a work supported by Science Popularization China Starry Sky Project

Team/Author Name: Global Science

Reviewer: Zhu Youan Associate Researcher, Vertebrate Paleontology (Ancient Fishes), Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.