This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The sights and sounds of the Jurassic era are long gone, and we will never know for sure what that ancient world looked and sounded like. Fossils can offer clues, and reconstructions can give us a sense of the noises some animals might have made.
Now scientists have turned their attention to insects and reconstructed the calls of Jurassic relatives of modern-day crickets and katydids (grasshopper-like insects). Details of the research have been published in the Proceedings of the National Academy of Sciences. In this study, scientists examined 20 fossilized wings from nine species of katydid relatives from Inner Mongolia, China, dating to around 165 million years ago in the Middle Jurassic.
In particular, they studied the microscopic, tooth-like ridges on the wings that make a noise when a scraper on the opposite wing rubs across them. The resulting sound is determined by the spacing of these ridges and the size of the vibrating wing area. To get an idea of what this may have sounded like millions of years ago, the team measured these structures on all the fossil wings.
They fed this information into computer models, along with data from modern insects and how the species were related, to figure out the frequency and basic structure of each ancient call. Then, a machine learning model estimated their likely call rate to build a hypothetical Jurassic soundscape. The results revealed a rich acoustic environment.
"We reconstructed their acoustic landscape, showing pure tone, diverse, and in some cases ultrasonic calls," wrote the research team in their paper. Many of the species studied produced pure-tone calls at pitches of around 5 kHz (kilohertz), similar to those of some living crickets. But one species, Sigmaboilus peregrinus, appears to have produced high-frequency ultrasonic calls above 20 kilohertz.
This is significant because it suggests insects used ultrasonic signals long before bats arrived on the scene. The flying mammals are often proposed as a driver behind the evolution of ultrasonic communication. "We here reject the hypothesis that bats were the sole driver of ultrasound evolution in katydids." According to the study authors, the diversity of acoustic signals may have served a useful purpose and kept the insects out of harm's way.
Extract — continue reading at the source.
