Scientists have recreated the ancient calls of Jurassic insects that echoed through woodlands 165 million years ago by examining fossilised wings discovered in northern China.
Researchers scanned microscopic structures on 20 fossilised wings from nine extinct species to reconstruct a prehistoric soundscape ranging from high-pitched chirps to ultrasonic signals.
Lead author Dr Fernando Montealegre-Zapata, an entomologist from the University of Lincoln in England, said the study provides fresh insight into prehistoric environments. "Our findings offer a glimpse into what a Jurassic forest might have sounded like," Montealegre-Zapata told the Daily Mail. "Far from being silent, these ancient environments were likely filled with a rich variety of sounds."
Microscopic Wing Analysis
While the delicate vocal cords and larynxes of dinosaurs rarely survive in the geological record, insect wings appear far more frequently as fossils. Insects use acoustic signals over long distances to search for mates, establish territory, and deter potential predators.
The ancient insects produced sounds through stridulation, a process of rubbing body parts together. Microscopic teeth-like ridges on one wing are scraped by a specialized structure on the opposite wing known as a plectrum. The frequency and tone of each call depended on wing shape and the exact spacing of teeth along the ridge.
Researchers examined fossils recovered from the Inner Mongolia region of northern China. The specimens belong to nine distinct species that represent the ancient ancestors of modern grasshoppers and katydids, which are also known as bush crickets. Despite their age, the sound-producing structures on the fossilized wings remained remarkably well preserved.
Laser Measurements and Machine Learning
To reconstruct the ancient calls, scientists scanned the fossil ridges under high-powered microscopes to build three-dimensional digital wing models. They validated these models against living insects by using laser measurements to record how modern wings vibrate during stridulation.
The team then applied a machine learning algorithm to calculate likely call rates and construct a hypothetical acoustic model of the Jurassic environment.
"Hearing the first reconstructed call was fascinating," Dr Montealegre-Zapata said. "It revealed that the way these insects produce sound has changed remarkably little since the Jurassic period."
"But the most extraordinary moment was hearing all the calls together," Montealegre-Zapata added. "These species likely lived side by side, and for the first time we could listen to a soundscape that may have filled Jurassic forests, much like the chorus of chirping insects we hear in tropical rainforests today."
Some of the reconstructed insect audio clips were incorporated into the soundtrack for the Netflix documentary series The Dinosaurs, produced by filmmaker Steven Spielberg.
Pure Tone Signals and Acoustic Survival
Many of the fossil species produced pure-tone calls, which concentrate acoustic energy into a narrow frequency band, similar to musical notes. To human ears, these sounds resemble high-pitched squeaks or beeps rather than a harsh, raspy rattle.
Pure-tone signals travel efficiently across noisy nocturnal environments. "This suggests these insects were communicating through highly specialised acoustic channels, allowing them to be heard by potential mates while making it harder for predators to pinpoint their location," Dr Montealegre-Zapata explained.
While several species produced pure-tone calls near 5 kilohertz, comparable to modern crickets, one specific insect named Sigmaboilus peregrinus developed high-frequency ultrasonic calls exceeding 20 kilohertz, which lies beyond the range of human hearing.
In modern ecosystems, roughly 70 percent of katydid species use ultrasonic communication. Paleontologists previously debated whether ultrasound evolved specifically to evade bats, which hunt nocturnal insects using echolocation. However, the presence of ultrasound in Sigmaboilus peregrinus demonstrates that insects developed high-frequency calls long before bats appeared.
An Ancient Acoustic Arms Race
Dr Montealegre-Zapata described the emergence of high-pitched calls as part of an evolutionary arms race between insects and early predators. As ancient predators developed sharper hearing, insects responded by shifting their calls to higher frequencies, eventually reaching ultrasonic levels.
This discovery indicates that early mammals in the Jurassic period may have developed sensitivity to high frequencies more than 100 million years before bats evolved.
"Rather than introducing ultrasound to a quiet environment, bats may have entered a soundscape that was already filled with ultrasonic signals," Dr Montealegre-Zapata noted. "In that sense, the Jurassic was not only noisier than we once imagined, but also acoustically more sophisticated."
Prehistoric Ecosystems and Extinction Context
The acoustic landscape of the Jurassic period flourished tens of millions of years before the catastrophic end of the Mesozoic Era. Dinosaurs and many contemporaneous species dominated the planet until their sudden disappearance around 66 million years ago in the Cretaceous-Tertiary extinction event.
Early theories attributed the mass extinction to gradual climate shifts that disrupted food chains. However, paleontologists in the 1980s discovered a global layer of iridium, an element rare in Earth's crust but abundant in space debris. A decade later, researchers identified the massive Chicxulub Crater on the tip of Mexico's Yucatan Peninsula, matching the exact timeframe of the iridium deposit.
Scientists agree that a massive asteroid impact generated catastrophic shock waves, widespread seismic activity, and global ash clouds that blocked sunlight, causing planetary cooling. While large dinosaurs perished, smaller organisms with shorter generational cycles survived, though alternative hypotheses suggest early egg-eating mammals or toxic flowering plants may also have contributed to dinosaur decline.
