The first known insect ears came from katydids 160 million years ago.

 

The chirps of insects known as katydids dominated the nighttime noises of Earth more than 100 million years ago. The appearance of the katydid ears that heard those noises is now known thanks to fossils.

The earliest known insect ears are 24 fossilised, roughly 160 million year old katydids that were discovered in China, according to a report published in Proceedings of the National Academy of Sciences on December 12.

The earliest short-range, high-frequency cries of any type may have been detected by these ancient sound sensors, which are identical to those present on modern katydids and may have assisted the insects in avoiding predators.

The ability to transmit sound waves through the air was initially developed by insects, enabling the critters to interact across greater distances than are frequently possible with sight.

The mid-Jurassic period, between 157 and 166 million years ago, is when male and female katydid ears first developed the ability to listen for possible mates or male rivals, according to analyses of the Chinese fossils. In Colorado, katydids and crickets held the previous record for the oldest insect ears, and they date back about 50 million years.

87 preserved male katydid wings from China, South Africa, and Kyrgyzstan, dating from around 157 million to 242 million years ago, feature sound-producing components that suggest they may have produced a range of chirps, including high-frequency cries up to 16 kilohertz. (In contrast, human hearing ranges from around 20 hertz to 20 kilohertz.)

Since high-frequency chirps don't go very far, katydids might have communicated over close ranges.