The clue comes from a fossil of an extinct fish ancestor named Shuyu. Its age is 438 million years.
The study of fish fossils over 400 million years old may seem like something unexpected and strange for the study of human anatomy. But as scientists have found, fish gills eventually became part of the ear of modern vertebrates, writes IFLS.
The bones of the middle ear convert the vibrations of the eardrum into more powerful sound waves that allow us to hear even very small interference in a wide frequency range. Their very interesting names translated from Latin as hammer, anvil and stirrup are familiar to everyone from school.
But a new study has shown that our middle ear developed from a spiracle – an evolved gill opening.
Some fish, whales, and sharks have spatter, but terrestrial vertebrates have evolved to use nostrils and mouths for breathing. In early tetrapods, the spiracles first developed into an auditory notch and later evolved into an ear, becoming an auditory canal that transmits sounds to the brain. This function has been preserved throughout human evolution.
It is important to note that the origin of the vertebrate spatter has long remained a great mystery to experts. However, in the course of a new study in China, experts found confirmation of their assumptions. They discovered a 438-million-year-old skull fossil of a vertebrate fish ancestor, named Shuyu. Reconstruction of Shuyu's skull revealed the presence of a spattered gill.
“Thanks to this fossil, we finally managed to get the first anatomical and fossil evidence that vertebrate spiracles originate from the gills of fish,” concluded one of the authors of the study, Dr. Zhikong Gai from the Chinese Academy of Sciences.