Using lasers, computer models, and AI, researchers reconstructed the sounds of a 165-million-year-old relative of modern crickets and katydids from fossilized feather fragments discovered in China. One of these fossil insects chirps at a frequency beyond human hearing, challenging the assumption that bat predation is what drove the insect into the ultrasonic realm.
“Little is known about the acoustic environments of long-gone landscapes like Jurassic forests,” wrote Dr. Jun-Jie Gu of Sichuan Agricultural University and colleagues in a paper.
“We are uncertain about the sounds made by dinosaurs and other charismatic vertebrates because their vocal organs are rarely well preserved in fossils.”
“Unlike the vocal cords of tetrapods, the sound-producing organs in the hardened epidermis of some arthropods often fossilize.”
“For instance, we can observe and measure beating structures (rasps, wasps) in fossil forewings of male crickets and their relatives.”
“These fossils carry traces of the acoustic signals they produced, offering a unique glimpse into the soundscapes of the past.”
In their study, the authors examined fossils of 20 ensiferan insects, the 7th species on earth. Prophalangopsidae and two of them Cucidae, an extinct family from the Triassic to Cretaceous periods, were unearthed from the Jiulongshan Formation in Inner Mongolia, China.
Dating back to the mid-Jurassic period, around 165 million years ago, the fossil preserves the delicate wing structures these insects used to create sounds by rubbing one wing against the other. heartbeat.
To interpret these ancient songs, researchers combined various techniques, including phylogenetic analysis comparing fossils with around 100 modern insect species, laser vibration measurements of modern insect wings, computer simulations demonstrating how fossilized wings vibrated, and machine learning models trained to forecast song patterns from wing shape.
The outcome was a remarkably diverse soundscape. Most of the nine species produced low, pure-tone calls around 5 kHz (kilohertz), resembling the sounds of some present-day crickets.
However, in some species, Sigmaboilus peregrinus appeared to be calling at frequencies above 20 kHz, in the ultrasonic range audible to humans.
This finding is significant because it precedes the arrival of bats, which emerged about 55 million years later and are traditionally believed to have facilitated the development of ultrasonic communication and hearing in insects as a defense against echolocating predators.
New evidence proposes that ultrasound signaling in insects was already established before the existence of bats.
This indicates that bats were not the sole driving factor behind the evolution of high-frequency insect calls.
Researchers suggest that early mammals and other predators may have exerted pressure on insects to produce quieter and more challenging to locate pure tone signals.
Competition for acoustic space among numerous calling species in congested environments may also play a role.
Fossilized wings of nine Ensiferan species analyzed by Gu others. Image credit: Gu others., doi: 10.1073/pnas.2615107123.
“For now, all we can confirm is that Jurassic ensiferans communicated over a wide range of frequencies, from low to moderately ultrasonic waves,” the authors state in their paper.
“We demonstrated that ultrasonic communication was likely embraced by the ancestors of katydids during the Middle Jurassic Period, around 165 million years ago. This marks the earliest documented instance of ultrasonic communication in animals.”
“Furthermore, these ancient ensiferans had already commenced diversifying their acoustic signaling strategies through alterations in body size and beat file morphology, producing pure-tone and high-pitched calls.”
“Though the observed diversity of acoustic signaling strategies and prevailing use of pure-tone ultrasound in present-day katydids are believed to be influenced by predator eavesdropping, we reject the notion that bats were the sole catalyst in the evolution of ultrasound in katydids.”
“Instead, early mammalian and non-mammalian ancestors may have also perceived ensiferan songs, promoting early diversification of acoustic signaling strategies.”
“The development of ultrasound may also have been motivated by acoustic niche partitioning due to interspecific competition.”
“Together with the proof of ultrasound in Cretaceous moths, it highlights that bats emerged almost a century following the ensiferan song bursting into a soundscape already buzzing with ultrasound.”
today, Proceedings of the National Academy of Sciences._____
Gu Junjie others. 2026. Reconstruction of extinct soundscape reveals ultrasonic communication in the Jurassic period. PNAS 123 (36): e2615107123;doi: 10.1073/pnas.2615107123
Source: www.sci.news
