Scientists recreate Jurassic soundscape from 150M-year fossil

Scientists have reconstructed part of a Jurassic forest soundscape by turning fossil insect wings into estimates of ancient calls. A study published in the Proceedings of the National Academy of Sciences said the team examined 20 fossilized wings from nine species of ensiferans — relatives of modern katydids and crickets — from the Jiulongshan Formation in Inner Mongolia, China, dated to about 165 million years ago. The researchers used preserved sound-producing structures on the wings to model how the insects likely chirped, including calls in both audible and ultrasonic ranges. ### How can a fossil wing preserve a sound? The PNAS paper said some insects make sound with hardened wing structures that fossilize well, unlike soft tissues such as vertebrate vocal cords. In these Jurassic specimens, the researchers focused on the stridulatory apparatus — a file of microscopic tooth-like ridges and the opposing scraper that would have rubbed across it to generate sound. (pnas.org) Phys.org’s summary of the paper said the team studied the microscopic ridges on the wings because those structures preserve a physical record of how the insects produced sound. That left the researchers with a rare fossil trace tied directly to acoustic behavior rather than just body shape. ### What exactly did the researchers do with those wings? The study said the team combined phylogenetics, laser Doppler vibrometry, numerical simulations and an AI-based approach to reconstruct the insects’ basic sound units and estimate carrier frequencies. (pnas.org) The fossils came from a single Middle Jurassic locality, which let the researchers model multiple species from one ancient ecosystem rather than one isolated specimen. (phys.org) Smithsonian Magazine reported that the work linked fossil measurements with data from living insects to estimate how the ancient wings vibrated and what frequencies they likely produced. That approach let the researchers move beyond saying an insect could make sound to proposing what that sound may have been like. (pnas.org) ### What did the Jurassic chorus sound like? The reconstructed calls varied by species, according to the paper and coverage of it, with some resembling lower musical chirps and at least some extending into ultrasonic frequencies above human hearing. The PNAS abstract materials described the work as a reconstruction of a lost soundscape, while Phys.org said the resulting calls evoked a 165-million-year-old forest. (smithsonianmag.com) The Smithsonian report said some of those calls would have been too high-pitched for humans to hear. That matters because it suggests Jurassic acoustic environments were more layered than the familiar image of a dinosaur-dominated landscape might imply. ### Why are scientists interested in the ultrasonic part? (pnas.org) The study’s broader significance is tied to timing. Coverage of the paper said at least one reconstructed signal indicates ultrasound in insects existed roughly 165 million years ago, well before bats evolved. TechTimes, summarizing the study, said the authors described this as the oldest ultrasonic record in any animal; that characterization should be read as reported in coverage unless confirmed directly from the full paper text. (smithsonianmag.com) Earlier PNAS work had already shown that Mesozoic katydids evolved high acoustic diversity, including high-frequency musical calls, and that evidence for fossil insect acoustic communication from this era is rare. The new paper expands that record from a single famous specimen to a broader community-level reconstruction. ### How complete is this picture of a Jurassic forest? The answer is partial by design. (techtimes.com) The study reconstructed insect calls from one group with fossilizable sound organs, not every sound in the ecosystem. A New York Times pickup summarized by DNYUZ said the soundscape accounts for only a small fraction of what would have echoed through Jurassic forests. The next step is already visible in the paper itself: the PNAS study provides reconstructed calls from nine species and a framework other researchers can apply to additional fossil insects from other sites and periods. (pnas.org) As more specimens are analyzed, the archive of ancient soundscapes could extend beyond the Jiulongshan Formation and further into the Mesozoic record. (pnas.org) (dnyuz.com)