Scientists reconstruct Jurassic cricket songs from 165-million-year-old fossils

The Jurassic wasn’t just about dinosaur roars. It was buzzing with cricket songs — and now we can actually hear them.

Researchers led by Thorin Jonsson from the University of Graz have reconstructed the mating calls of nine grasshopper species that lived during the Middle Jurassic in what is now Inner Mongolia, producing the oldest traces of sound ever recovered on Earth.

The findings, published in PNAS with colleagues from Lincoln, Bristol, Beijing and Tempe, were made possible by exceptionally well-preserved fossils.

Insects from the order Orthoptera — crickets and grasshoppers — produce sound by rubbing wing structures against each other or their legs, called stridulation. Pitch and rhythm depend on the number and spacing of teeth on the wing’s ridge and the shape and movement of wings.

While vocal cords don’t fossilize, those wing imprints do — and they act like musical notation.Using detailed analysis, simulations and AI-assisted evaluations, the team could calculate the exact hertz each insect sang at.”Our findings reveal a wide variety of call frequencies. Several species produced pure, low-pitched sounds like modern crickets, whilst others produced higher frequencies, similar to our native leafhoppers,” Jonsson said.

One species surprised them: a katydid relative called Sigmaboilus peregrinus communicated at 20-22 kilohertz — just above human hearing range.

That finding rewrites a theory. Scientists previously thought insects evolved ultrasonic calls to evade bats’ precise hearing. But S. peregrinus lived millions of years before the first bat existed.

The team hypothesizes it may have been to avoid other predators, or a mating strategy to rise above the din of a Jurassic night.”This allowed us to demonstrate that the world during the Jurassic Period was acoustically far richer and more diverse than previously thought,” Jonsson said.