Daily Weird News Report
The Jurassic forests may have been filled with insect calls that no human could hear. Using fossilized wings and computer modeling, scientists have reconstructed simulated sounds from insects that lived about 165 million years ago.
The study, published August 25 in the Proceedings of the National Academy of Sciences, examined 20 fossils discovered in Inner Mongolia, China. The specimens represented nine species related to modern crickets and katydids, with their wings preserved well enough to reveal the structures used to produce sound.
Unlike animals that use vocal cords, crickets, grasshoppers and katydids generally make noise through stridulation: rubbing ridged body parts together. Crickets move one wing across another, while grasshoppers and katydids typically rub a leg against a wing. Because wings and other external structures can fossilize, they provide clues about how these insects produced sound.
The researchers analyzed the number and spacing of ridges on the fossil wings, along with the size of the areas that would have vibrated. They compared those features with the sound-producing mechanics of living insects, which they studied using lasers. Evolutionary relationships among the fossil species were also included in computer simulations, while an artificial intelligence model predicted the likely pattern of each call.
Most of the reconstructed insects appear to have produced relatively low-frequency sounds of around five kilohertz. The calls were likely “pure tones,” meaning they would have resembled clear, high-pitched chirps rather than hisses or buzzing sounds.
One species, Sigmaboilus peregrinus, may have produced calls between 20 and 22 kilohertz. That range is at or just above the upper limit of human hearing and is considered ultrasonic when it exceeds 20 kilohertz.
The finding complicates the idea that bats drove the evolution of ultrasonic insect calls. S. peregrinus lived millions of years before the first bats, so the researchers suggest that other predators—or competition among different insect species—may also have encouraged the development of high-frequency sounds.
The scientists say the same approach could eventually be used to reconstruct sounds made by other fossil insects, including beetles and ants. For now, the simulations offer a glimpse of an ancient soundscape whose actual recordings could never have survived.
