The Jurassic period resonated with far more than the thunderous footsteps and roars of dinosaurs. Scientists have successfully recreated the chirps and songs of ancient insects that filled the air 165 million years ago, offering an unprecedented glimpse into the acoustic environment of prehistoric Earth.
Thorin Jonsson from the Institute of Biology at the University of Graz led an international research team that analyzed remarkably preserved fossils to reconstruct these ancient sounds. The findings, published in the journal PNAS, represent the oldest evidence of sound ever reproduced by researchers.
The breakthrough came from examining fossils of nine different grasshopper species discovered in what is now Inner Mongolia. These insects lived simultaneously in the same region during the Middle Jurassic period, and their remains preserved intricate details of their sound-producing anatomy.
Collaborating institutions included the universities of Lincoln, Bristol in the United Kingdom, Beijing in China, and Tempe in the United States. The Chinese research partners provided the exceptionally well-preserved fossil specimens that made the acoustic reconstruction possible.
Insects from the order Orthoptera, which includes modern crickets and grasshoppers, produce sounds through a process called stridulation. They rub specialized wing structures against one another or against their legs to create distinctive chirps and songs. The pitch and rhythm depend on the number and spacing of teeth on the wing's ridge, along with the shape and movement of the wings themselves.
While vocal cords and other soft tissue acoustic organs cannot survive the fossilization process, the wing imprints preserved in stone contain precise information about how these ancient insects communicated. The research team employed various analyses, simulations, and artificial intelligence-assisted evaluations to decode these physical features and determine the exact frequencies each species produced, measured in hertz.
The reconstructed soundscape revealed unexpected diversity. According to the published research, Jonsson reported that several species produced pure, low-pitched sounds resembling modern crickets, while others generated higher frequencies similar to contemporary leafhoppers.
The achievement parallels the famous Epitaph of Seikilos, a Greek funerary song inscribed on a gravestone that musicians can still read and perform thousands of years after its composition. Similarly, the physical features on the ancient grasshoppers' wings function as a form of musical notation. While researchers cannot reproduce these sounds on traditional instruments, artificial intelligence can simulate them using computer sound boards.
One species among the nine fossils particularly surprised the research team. Sigmaboilus peregrinus, a relative of the modern katydid, communicated in the ultrasonic range between 20 and 22 kilohertz. This frequency sits just above the threshold of human hearing.
The discovery carries significant implications for understanding the evolutionary biology of Orthoptera. Scientists previously theorized that insects developed ultrasonic stridulations as a defensive adaptation against bats, whose exceptionally precise hearing could detect lower-frequency insect calls. However, Sigmaboilus peregrinus existed millions of years before the first known bat appeared in the fossil record.
The research team proposed alternative explanations for why an insect would vocalize at such high frequencies in the absence of bat predation. The ultrasonic calls may have helped the insects avoid detection by other predators that hunted using sound. Another possibility involves mating strategy, with males producing high-frequency calls that could cut through the cacophony of other insects filling the Jurassic night.
The biologist summarized the study's broader significance, noting that the research demonstrates the Jurassic period possessed an acoustically far richer and more diverse soundscape than previously understood. The findings challenge assumptions about prehistoric environments and reveal that the ancient world buzzed with complex communication systems long before the evolution of many modern animal groups.
