On a warm summer evening, park pathways hum with the crisp chirps of bushcrickets and katydids. These ephemeral acoustic vibrations radiate through the dusk and vanish within seconds, leaving no trace behind. Yet 165 million years ago, deep in the lush canopies of a Jurassic rainforest, katydids were already singing to attract mates — and today, modern science has faithfully resurrected their prehistoric songs.
In a landmark international study published in the Proceedings of the National Academy of Sciences (PNAS) on August 25, 2026, palaeobiologist Jun-Jie Gu of Sichuan Agricultural University and collaborators from the University of Lincoln in the UK achieved an extraordinary acoustic breakthrough. Analyzing 20 remarkably preserved insect wing fossils unearthed in Inner Mongolia, China, the team computed and reconstructed an ancient Jurassic soundscape. The research shatters the traditional view of fossilization: stones preserve far more than mineralized skeletons; when delicate acoustic machinery fossilizes, even transient sound waves can be decoded from stone.
Stones Can Preserve Bones — and an Ancient Song
When thinking of the age of dinosaurs, people typically envision the thunderous roars of apex predators. Yet dinosaur vocal organs consisted primarily of soft tissue, virtually incapable of surviving millions of years of geologic wear. Ancestral katydids (crickets and bushcrickets belonging to the order Orthoptera), however, left humanity the key to an ancient acoustic vault. Their forewings were composed of durable chitin — the tough biopolymer forming insect exoskeletons — capable of enduring sediment deposition for hundreds of millions of years.
Gu’s team collected 20 exceptionally preserved katydid wing fossils from the Jiulongshan Formation in Daohugou Village, Inner Mongolia, spanning nine extinct species. Gu noted that while most fossils document static anatomy and skeletal morphology, these specimens captured the most fleeting phenomenon of all: sound. By unraveling the mechanical physics of orthopteran sound generation, each fossil wing effectively becomes a prehistoric vinyl record waiting to be played.
Figure: Close-up of a Jurassic male katydid fossil unearthed in China. Source: Science News
Microscopic Teeth Form a Natural Violin
The mechanism by which male katydids produce sound is functionally identical to playing a miniature acoustic violin. On the underside of the left wing runs a file-like ridge of microscopic teeth, known as the stridulatory file. Along the inner margin of the right wing sits a hardened blade called the plectrum, or scraper. When the insect rubs its wings together, the plectrum scrapes across the teeth at thousands of impacts per second, driving microscopic vibrations that resonate across the wing surface to produce piercing, high-decibel calls.
The spacing between individual teeth along the file measures only a few dozen micrometers — far finer than a strand of human hair. By analyzing morphological data from 95 living katydid species, the researchers observed a clear biomechanical rule: the shorter the stridulatory file and denser the teeth, the higher the wing vibration frequency and the more acute the resulting pitch. Using a laser Doppler vibrometer to record microscopic resonance in modern relatives, the team validated the accuracy of reverse-engineering acoustic frequencies directly from wing geometry.
Figure: A modern katydid perched on foliage. Source: Science News
Calculating the Polyphonic Choir of the Jurassic Canopy
Armed with quantitative fossil measurements, the team constructed finite element numerical models to simulate the intrinsic resonance frequencies of all 20 fossil wings. The results revealed that different Jurassic katydid species occupied distinct acoustic niches across the canopy. Larger species produced resonant chirps centered around 5,000 Hertz (5 kHz), closely matching the timbre and pitch of a modern piccolo.
Beyond fundamental frequencies, the researchers leveraged machine learning algorithms to model chirp cadences by factoring in body mass and estimated Jurassic ambient temperatures. Higher temperatures enable faster insect muscle contraction, yielding a tighter, more rapid tempo. Synthesizing these physical parameters produced the oldest high-fidelity acoustic map of a terrestrial ecosystem known to science.
Evolving Ultrasound 100 Million Years Before Bats
Among the nine reconstructed species, one particular fossil insect — Sigmaboilus peregrinus — stood out. Mathematical modeling demonstrated that its carrier frequency reached a staggering 20,500 Hertz, surpassing the 20,000 Hertz threshold of human hearing. In the prehistoric Jurassic night 165 million years ago, the canopy resonated with high-frequency ultrasonic waves completely inaudible to human ears.
In modern ecosystems, insects typically deploy ultrasonic frequencies to evade the biosonar echolocation of bats. This ancient ultrasonic discovery fundamentally challenges established timelines: the earliest ancestral bats did not appear until the Eocene epoch, roughly 100 million years after these katydids sang. Ultrasound communication in insects evolved long before the emergence of flying mammalian predators, propelled instead by terrestrial hunters on the forest floor.
Pure Tones: Acoustic Camouflage Against Early Mammalian Ears
Physical analysis revealed that these Jurassic katydid calls were distinct pure tones — acoustic signals concentrated within an exceptionally narrow frequency band. Unlike broad-spectrum noise, a pure tone radiating through dense vegetation makes interaural time-difference localization exceptionally difficult for predators. Biologist Daniel Robert of the University of Bristol noted that pure-tone songs allowed katydids to broadcast loud mating advertisements to conspecific females while minimizing the risk of revealing their spatial position to hunters.
Fossils from the same Daohugou beds indicate that early shrew-like insectivorous stem-mammals already roamed the undergrowth, possessing inner ear structures capable of detecting mid-to-high frequencies. Faced with predators possessing ever-improving acoustic hearing, ancestral katydids shifted their communication upward into the ultrasonic spectrum, sparking an evolutionary acoustic arms race in the earliest terrestrial biomes. As University of Chicago paleontologist Zhe-Xi Luo commented, this hypothesis of co-evolution between vocalization and auditory predation highlights the intricate behavioral complexity of deep-time ecosystems.
From micro-teeth tens of micrometers wide to the rebirth of a 165-million-year-old serenade, modern science demonstrates how fleeting acoustic codes endure in stone. The physical architecture of sound organs — tooth spacing, wing surface area, and resonant geometry — fully encodes acoustic frequencies, transforming the most ephemeral sound waves into quantitative physical fossils. Listening to insects in the warm summer grass today, one realizes that rocks do not merely preserve inanimate bones: they keep eternal records of the songs of the ancient Earth.
Reference Links:
- Science News: A choir of katydid ancestors filled the Jurassic rainforest with song
- PNAS Original Paper: Reconstruction of an extinct soundscape reveals ultrasonic communication in the Jurassic
- Science News: Katydids had the earliest known insect ears 160 million years ago
