Nature
PUBLISHED
While scientists and researchers have gotten pretty good at reconstructing dinosaurs and learning what ancient plants might have looked like, there is one area that still proves tricky to recreate: sound.
However, by taking a closer look at some ancient insects, a team has come up with a hypothetical Jurassic soundscape made up of insect noises from 165 million years ago.
Given that the soft tissue of dinosaurs rarely fossilizes, the team turned to insects to look at their fossilized sound-producing organs. Overall, the team studied 20 fossils from the Ensifera, a suborder of insects that includes crickets and katydids, that were all found in a similar area in what is now Inner Mongolia.
The fossils represent nine species that all had well-preserved sound-producing organs, such as parts found on their wings, known as files and plectrums, that when rubbed together produce various noises. This way of producing sound is still seen today in living species, and can therefore help infer what kind of noises were made in the Jurassic.
By using living species as a basis, the team used micro-scanning laser Doppler Vibrometry to measure wing resonance, damping, areas that vibrate, and wing mechanics.
They could then construct 2D models of the wings, which allowed them to apply the same process to fossilized wings to recreate what they might have sounded like. It's helpful that at least the basic way of producing song in these insects has not changed since the late Triassic.
During the process, the team discovered that the insects produced noises with pure tones like music. This reflects in a very narrow frequency, so the noises would have sounded like clear, high-pitched notes.
The team thinks this would have allowed the insects to communicate in a noisy landscape, but at the same time prevented predators from being able to locate them. This might even have pushed the insects into producing ultrasound noises, many millions of years before bats even evolved.
“A pure tone is a musical tone,” says Fernando Montealegre-Zapata, a sensory biologist at the University of Lincoln and one of the study’s lead researchers, told Science.
“You hear a cricket singing, but try to localize it,” Montealegre-Zapata says. “You really can’t.”
However, the study is limited. The models can predict basic sound and pitch, but they can't go as far as to include rhythm or any pattern to the songs. Even so, the models created by the researchers were still enough to construct a hypothetical Jurassic soundscape.
“For now, we can only confirm that Jurassic Ensiferans were communicating with a broad range of frequencies from low audio to moderate ultrasound,” explain the authors in the paper.
“We show that ultrasonic communication was likely adopted by katydid ancestors during the Middle Jurassic, some 165 ma, the oldest record known for ultrasound communication in animals.”
The paper is published in PNAS.
